Author: Charles Stewart, MD, FACEP, Associate Professor of Emergency Medicine, University of Rochester School of Medicine, Rochester, NY.
Peer Reviewers: Stephen A. Colucciello, MD, FACEP, Clinical Services Director, Trauma Coordinator, Department of Emergency Medicine, Carolinas Medical Center, Charlotte, NC.
Justin Kaplan, MD, Research Co-director, Department of Emergency Medicine, Albert Einstein Medical Center of Philadelphia, Philadelphia, PA.
The knee is one of the most frequently injured joints in the body and can have a bewildering array of injuries.1 Since it is a weight-bearing joint, it is constantly subjected to substantial force. Unfortunately, the knee is found at the end of two relatively long lever arms, so a modest amount of force beyond "design limits" can cause a major disruption of the joint. Falls, automobile accidents, and virtually any sports activity can result in an acute knee injury.
Despite the frequency of injuries and the resultant wide experience with their management, consensus standards for the treatment of many acute knee injuries do not exist. In addition, the initial bedside diagnosis of intra-articular ligamentous and cartilaginous injuries is imprecise. As such, the expeditious diagnosis and referral of patients with traumatic hemarthrosis and/or suspected ligamentous injury is most likely to yield optimal results.2 The emergency physician is in an ideal position to facilitate early diagnosis and surgical repair when appropriate.
This review of acute knee trauma will focus on anatomic essentials and examination and imaging techniques. Special attention will be given to ligamentous, meniscus, and fracture/dislocation injuries.
The Editor
The knee is a hinge joint with a range of motion from about 0° in full extension to about 130° of flexion. There is some rotational flexibility in the knee joint, but this varies from patient to patient. There are three bones, four ligaments, and two cartilages included in the knee. These are augmented by the extensor and flexor mechanisms. The bony knee is formed by the articulation of the distal femur, the proximal tibia, and the posterior aspect of the patella. Although the proximal fibula is an attachment for ligaments that support the joint, it is not part of the knee joint articulation. (See Figure 1.)
There is no inherent stability to the knee joint. All stability is provided by the ligamentous structures that surround the knee. Anterior and posterior stability is provided by the two cruciate ligaments, with the posterior cruciate providing most of this stability. The medial and lateral collateral ligaments stabilize the knee in side-to-side motion. Finally, the meniscal cartilages provide some stability, but they mostly act as shock absorbers for the knee.
The extensor mechanism of the knee is the quadriceps femoris muscles, the quadriceps tendon, the patella, the patellar tendon, and the insertion of the patellar tendon into the tibial tubercle. Four muscle groups comprise the quadraceps femoris: the superficial rectus femoris, the vastus medialis, vastus lateralis, and the deeper vastus intermedius muscles. Fibers of the rectus femoris invest the patella and contribute to the patellar tendon. The patellar tendon inserts into the anterior lip of the tibia and the tibial tubercle.
The approach to an acute knee injury depends, in part, on when the patient presents to the ED. In most cases, there is little problem with the history. The patient comes to the department with a history of force applied to the leg or knee directly. This may be caused by a sporting accident, an automobile accident, or a fall. Certain mechanisms provide clues to diagnosis: "catching a tip" while skiing leads to anterior cruciate ligament (ACL) tear; a side tackle in football leads to a medial collateral tear; a head-on motor vehicle accident (MVA) may produce rupture of the posterior cruciate.
Many of the injuries that occur to the knee involve more than one ligament. It is essential to appreciate this fact before attempting to diagnose the condition.
If the emergency physician is careful in obtaining a mechanism of injury and appropriate history, then the diagnosis may be obvious prior to examination of the knee. Acute swelling may mean bleeding from a fracture or torn ligament. Immediate loss of extension may indicate a cartilaginous tear, a loose foreign body, or rupture of the extensor mechanism (quadriceps or patellar tendon). Contact injuries may involve a valgus load that will first tear the medial collateral ligament (MCL), then the posterior medial capsule of the knee and, finally, the ACL. This is known as O’Donaghues’ triad.3 A force that produced hyperextension will first disrupt the ACL, then the posterior cruciate ligament.
The examiner should be wary of hip problems (such as slipped capital femoral epiphysis) that present with knee pain, especially in children. A complete examination should include palpation of the hip and complete range of motion of the hip. Pain with flexion, internal rotation, or external rotation should suggest a possible hip fracture, Legg-Perthe’s disease, avascular necrosis, or arthritis of the hip. If there is any question of referred pain or concomitant hip injury, then radiographs of the hip should also be obtained.
Most acute knee injuries can be completely evaluated with an adequate history that includes mechanism of injury and careful examination of the knee. The emergency physician must master the physical examination of the acutely injured knee. (See Table 1.)
When examining the patient’s knee, the patient should be supine, since this relaxes the muscles of the leg.4 Sitting up will contract the quadriceps. Hanging the leg off of the side of the bed will obscure many findings but does allow for visualization of active flexion beyond 90°. Examination of the patient in a wheelchair is completely inadequate.
Inspection of the knee joint may reveal ecchymosis about specific structures. Areas of ecchymosis should be examined closely to check the underlying structures. The most common areas are the tibial tubercle, the MCL, the patella, the iliotibial band, and the postero-lateral aspect of the knee. Inspection may reveal lacerations that can potentially invade the knee joint, as well as evidence of swelling or patellar dislocation.
Palpation. Palpation is one of the most important sections of the physical examination of the knee. It is wise to start away from the area of injury and work toward the injury. This will allow the examiner to establish a rapport before starting the painful part of the examination. If a fracture is strongly suspected, the emergency physician should defer stressing the knee until after radiographs are taken. If a significant fracture is present, stressing the knee to determine ligamentous laxity is unnecessary and potentially harmful.
Palpate the course of the collateral ligaments and the posterior corners of the joint capsule. Tenderness along the course of the collateral ligament should point the examiner toward an injury of that ligament, while tenderness in the joint line may mean a meniscal tear. Patellar tendinitis and chondromalacia patella may be associated with tenderness at the inferior portion of the patella. Palpate the epiphyseal plates in children and adolescents so that a nondisplaced epiphyseal injury is not missed.
An acute hemarthrosis may be found on examination of the knee. This finding usually indicates serious injury to one or more structures of the knee. The most common injury is to the ACL (about 70% of cases). Peripheral meniscal tears make up another 10% of cases. Patellar subluxation is seen in about 10-15% of cases, and osteochondral fracture fragments occur about 5% of the time.5 Meniscal and cruciate ligament tears may co-exist in as many as 60% of the cases.5 Osteochondral fractures are the predominant injury associated with ACL tears in children.
Extensor Mechanism. Determine whether the patient can raise the leg straight against gravity. If the patient cannot do this, then look for a fracture of the patella or rupture of the quadriceps tendon. Quadriceps rupture occurs when there is a sudden stop during active extension, as in stumbling forward. Patellar tendon ruptures and fractures of the tibial tubercle should also be considered.
McMurray Test. A positive McMurray test is indicative of a cartilaginous tear. It is performed by hyperflexing the knee, internally rotating it, and extending the knee while palpating the knee joint. The knee is then hyperflexed and externally rotated. If the examiner feels a crunch, grind, or pop in the joint line, the test is positive.
Drawer Test. The drawer test determines the integrity of the ACL. Have the patient lie supine on the examination table and flex the knee to 90° with the foot planted flat on the table. Stabilize the foot with your body. Wrap your hands around the knee with the fingers in the areas of insertion of the medial and lateral hamstrings and the thumbs on the joint line. Put the thumbs in the joint line to feel a step-off. Draw the tibia toward you. If it slides under the femur toward you, the ACL may be torn. A little anterior draw is normal if present on both sides. The anterior drawer test is unreliable in the acutely injured knee because of pain and swelling.
It the test is positive, repeat with the leg in internal and external rotation. External rotation will tighten the postero-medial portion of the joint capsule, so there should be reduction of the motion, even when the anterior cruciate is torn. When there is no reduction of the motion, suspect that both the anterior cruciate and the posterior medial potion of the joint capsule were damaged. Internal rotation demonstrates tears of the postero-lateral joint capsule.
The posterior cruciate (posterior-drawer test) is tested by pushing on the tibia rather than pulling. If it moves posteriorly, then the posterior cruciate may be damaged. Isolated tears of the posterior cruciate ligament are not common. Normal knees have no posterior excursion.
Lachman’s Test. The Lachman’s test is more sensitive than the anterior drawer test for acute rupture of the ACL. (See Figure 2.) The knee is placed in full extension while the distal femur is elevated, thereby permitting the knee to flex. Next, the proximal tibia is pulled anteriorly in an attempt to displace the tibia on the femur. If the tibia moves forward excessively on the femur, the test is positive. The result that should be noted on the chart is the maximum displacement of the knee at the joint line. This should be compared to the opposite side. A difference of more than 2.5 mm from side to side is diagnostic of a tear of the ACL in most cases.6 A partial tear may allow an elastic rebound to the pull rather than a full, firm stop. The Lachman’s test is much more sensitive for an anterior cruciate tear than the standard drawer test. The Lachman’s test can also be done for a posterior cruciate injury by pushing rather than pulling.
Pivot-shift Test. The pivot-shift test reproduces the instability experienced by the patient. The knee is examined in full extension, the tibia is internally rotated, with one hand grasping the foot and the other hand applying lateral (valgus) stress at the knee joint. The knee is then flexed to about 20-30°. The examiner will feel a jerk at the anterolateral corner of the proximal tibia. The Lachman’s test is probably a better test for ACL insufficiency than the pivot-shift test.
Like the Lachman’s and the anterior drawer tests, the posterior cruciate ligament can be tested by reversing the directions above. The examiner supports the limb with a hand under the heel, the knee in full extension, and then applies a mild valgus stress with the other hand on the patient’s lateral calf and flexes the knee. If the test is positive, the tibia will externally rotate and the lateral tibial plateau will subluxate. When the knee is extended, the tibia will reduce. Unlike the Lachman’s and anterior drawer tests, the reverse pivot-shift test is probably the best test for a posterior cruciate ligament injury.
Collateral Ligaments. To test the medial aspect of the knee for stability, push medially against the knee and laterally against the knee to open the knee joint on the medial side. Palpate the medial joint line for gaps. If there is a gap, then the medial collateral ligament is torn. These gaps may be either palpable or visible. When the stress is released, the examiner may feel a "clunk" as the tibia and femur close.
Palpate the medial surface of the medial femoral condyle for tenderness. This is the area where the MCL is most often torn.
Since the MCL is more crucial to stability than the lateral collateral ligament, a complete tear may cause joint instability. Most collateral ligament tears are medial.
To test the lateral aspect of the knee for stability, push laterally against the knee and medially against the knee to open the knee joint on the lateral side. Palpate the lateral joint line for gaps. These gaps may be either palpable or visible. When the stress is released, the examiner may feel a "clunk" as the tibia and femur close. Both lateral and medial stability should be tested with the leg in full extension and in 20° flexion. The extended-knee exam tests the posterior capsule. By flexing the knee, the posterior capsule becomes lax, and the collateral ligaments are tested in isolation.
Patellar Apprehension Test. To perform the patellar apprehension test, the examiner will attempt to laterally displace the patella in extension, at full hyperextension, and at 30° of flexion. This test is sensitive but not always specific. If there has been a recent dislocation of the patella, the patient will be apprehensive of the examiner’s attempt to push on the patella.
Aspiration of the Knee. Aspiration of the hemarthrosis often markedly relieves the patient’s pain and provides a good clue to diagnosis of the injured knee. Seventy-two percent of bloody effusions are caused by a tear of the cruciate ligament.7 Conventional wisdom states that if the effusion contains fat globules, a fracture should be suspected, though data substantiating this point are lacking. If the physician instills 10 cc of 1% lidocaine into the joint and then re-examines the knee, additional pathology may be unmasked, and the patient will be far more comfortable. A combination of marcaine and morphine in the joint gives up to 48 hours of pain relief. A Lachman’s or pivot-shift test may be possible to perform after the patient’s knee has been aspirated and the hemarthrosis drained.
The technique is simple and rapid. Although the effusion may reaccumulate, it can be slowed by ice, elevation, and a compression dressing of the knee. The emergency physician should not hesitate to perform this diagnostic and therapeutic technique.
When the patient presents with a possible knee injury, the evaluating physician can choose from conventional radiography, imaging with tomography, skeletal scintigraphy, arthrograms, arthroscopy, computed tomography, and magnetic resonance imaging (MRI). The costs, capabilities, and limitations of these techniques must be appreciated by the diagnostician. Each of these techniques gives additional information at an incremental cost to the patient. The emergency physician should realize that only rarely will his or her emergency therapy be changed by one of these advanced techniques. (See Table 2.)
Plain Film Radiographs. The standard knee series varies from institution to institution. The ideal approach involves establishing a presumptive diagnosis after a careful examination before ordering radiographs. A standing anteroposterior (AP) view of the injured knee, or a regular AP if the patient cannot stand, is standard. Lateral, oblique, and notch views may also be obtained. The cross-table lateral view may reveal a blood/fat level in the joint which is pathognomonic of a fracture. The oblique view may demonstrate a fracture or loose foreign body in the joint. The notch view will allow evaluation of an osteochondral fracture. The sunrise view demonstrates the patella. If a plateau fracture is suspected despite normal films, consider a plateau view of the knee.
The plain films can show intra-articular effusions, fractures, tendinous calcifications, and most foreign bodies. They are not particularly helpful in diagnosis of soft-tissue and many cartilaginous and osseous abnormalities. In part, abnormalities of movement are often rotatory, and the conventional films will not demonstrate these problems. If the cortex of the bone is violated, or the periosteum is stimulated or displaced, the injury will usually be seen on a plain film of the knee. The five ligaments of the knee are not seen at all on plain films.
There are not significant radiographic clues to the diagnosis of medial collateral tears. A valgus force may cause a lateral tibial plateau fracture in the older patient. There are a number of radiographic findings that may help to make the diagnosis of a lateral collateral injury. The capsule may tear a bony fragment from the proximal tibia. Likewise, the head of the fibula may be avulsed in a lateral collateral or biceps femoris injury. A tibial spine injury may suggest a tear of the cruciate ligament.
Recently, rules similar to the Ottawa Decision Rules for ankle injuries have been applied to knee injuries.8-11 The reliability of these decision rules has not yet been established in multiple settings. Given the current moves toward cost-containment in medical care and the obvious overuse of radiography, a reliable tool to support clinical decision making is needed. Further work is necessary before widespread adoption of decision rules is appropriate.
Magnetic Resonance Imaging. There has been an explosion of interest in MRI since 1985. The major reason for the rapid acceptance of MRI in the diagnosis of acute and chronic knee injuries is that it provides additional clinical information that is not easily obtained by any other imaging technique, including arthrograms and arthroscopy.12 This should be considered an advanced imaging technique. Only rarely should the emergency physician even consider employing MRI in the emergency management of the acute knee injury.
In many centers, MRI has completely replaced arthrograms for the investigation of the internal disorders of the knee, since MRI has superior tissue-contrast resolution and is totally noninvasive.13 There is no need for intra-articular contrast injection and no use of ionizing radiation. MRI is not limited to the surface of the joint or only to the surfaces that can be exposed by arthroscopy. Using MRI, the physician can evaluate more structures than just the bones, cruciate ligaments, and the surfaces of the menisci. The MRI can show both internal and external meniscal abnormalities. Osteochondral injuries, such as osteochondritis dissicans or traumatic osteochondral fracture, can be easily seen on MRI. MRI can also show acute or chronic damage to the articular cartilages of the tibia, femur, and patella. Tears of the anterior cruciate that are difficult to diagnose in the presence of a significant joint effusion are easy to find on MRI. These cruciate ligament tears are diagnosed on physical examination about 85% of the time but are seen 95% of the time on MRI. Rupture of the extensor tendon mechanism at either the patellar tendon or the quadriceps femoris is most easily diagnosed by MRI.14
The major disadvantage of MRI is its high cost. Since the MRI is both new and fairly expensive, cost-benefit ratios in the evaluation of acute knee injuries have not yet been determined. A more detailed knowledge of the anatomy and pathology is required as more anatomic areas are now visible and more diseases able to be diagnosed in the knee.
Arthroscopy of the Knee. The knee is the largest joint in the body and, as such, is the most amenable to both visualization and operative repair of lesions. Initially, diagnostic arthroscopy allows assessment of meniscal and cruciate ligament injuries. Arthroscopy of the knee is usually accomplished through an anterolateral port, and evaluation of the inferior surface of the posterior part of the medial meniscus is quite difficult.15 Other areas that are difficult to see with an arthroscope include the peripheral attachments of the meniscus on both sides and the posterior section of the lateral meniscus. Evaluation may include performance of a drawer test during the arthrogram.
The arthroscope can be used not only to diagnose knee injuries but, in skilled hands, repair them. The resulting morbidity of the athlete is markedly reduced, with far shortened times in both hospital and recuperation. Meniscal repair through the arthroscope allows the patient to return to full activity sooner and, possibly, with a decreased likelihood of complications than with open surgery.16 Needless to say, arthroscopy is not an emergency medicine procedure.
Ultrasound. Ultrasound scanning can display lesions in ligaments with considerable accuracy. It is more accurate than CT scanning but somewhat less accurate than MRI.17 With the availability of relatively inexpensive and more accurate MRI, ultrasound examination of the knee has been largely supplanted.
Anterior Cruciate Ligament Sprain. Incidence. The ACL is the most commonly injured major ligament of the knee, with these injuries occurring predominantly during non-contact sports. It also has the potential for causing the greatest disability. Early diagnosis decreases further injury and shortens the time until resumption of normal activity.
Anatomy and Function. The ACL attaches to the posterior aspect of the lateral femoral condyle and to a fossa just anterior and lateral to the anterior tibial spine. The tibial attachment is broad and extends into the lateral meniscus. The femoral attachment is a semicircle, with the anterior border straight and the posterior border convex. There are two major bundles within the ligamentthe anteromedial and the posterolateral. The anteromedial bundle tightens during flexion, and the posterolateral bundle tightens during extension. This means that the ligament is under tension, and hence, at risk during all motions of the knee.
The vascular supply is almost exclusively from the synovial covering. There is little blood supply from the bony attachments. The nerve supply is mechanoreceptors with only scant pain fibers.7 Since there are few pain fibers, ACL tears may not hurt much.
The ACL has five major functions: controling and resisting internal rotation of the femur and the tibia, resisting displacement of the tibia anteriorly on the femur, preventing hyperextension of the knee, acting as fine-tuning for the locking mechanisms of the knee, and restraining against valgus and varus strain in flexion of the knee. Of these functions, perhaps the prime role is to prevent internal rotation of the flexed knee on the femur.
History. The ACL is the most frequently injured ligament in the knee.18 No single common mechanism causes rupture of the ACL, although a twisting motion of the knee is a common one. (See Table 3.) Basketball, football, soccer, and, to a lesser extent, rugby are common sports in which this injury occurs. Failure of ski binding to release may be associated with an anterior cruciate tear. The patient may note a "pop" or tear at the time of the injury.19
The patient may describe hyperextension of the knee by falling while playing basketball or missing a dismount in gymnastics. Basketball, football, soccer, and rugby players may attempt to stop suddenly in order to change directions. This appears to produce a quadriceps contraction that displaces the tibia anteriorly. Skiers may injure the ACL when they catch the outside edge of a downhill ski and both extend and internally rotate the tibia on the femur.
The patient will usually complain of posterolateral knee pain, immediate swelling of the knee, and varying degrees of knee instability. The patient may be unable to continue to play or walk but may also have sufficient stability of the knee to walk off of the field. A tense, bloody knee effusion is common, but if there is sufficient disruption of the joint capsule, the blood may extravasate into the surrounding tissues. Early application of ice may delay the hemarthrosis. Intense pain may develop within hours as the swelling from hemarthrosis ensues.
Examination of the acutely swollen knee is usually difficult and often unrewarding. A positive anterior drawer or Lachman’s test is strongly suggestive. The anterior drawer test is often normal in acute injuries because the meniscus may block the forward motion of the tibia, or the hamstring spasm may prevent forward motion in the patient with a tense effusion of the knee.
Classic symptoms and signs of complete ACL tear are: the knee gave way, buckled, or "popped," there is a question of the patient being able to continue activity, or there is acute hemarthrosis within the first few hours.
Unfortunately, some athletes will have a tear of the ACL and not only have minimal symptoms but may return to the game rapidly.7 In these patients, diagnosis may be difficult. Some patients will develop a secondary degenerative arthritis of the knee, while others will show little joint deterioration. Since the presentation of the ACL injury is so variable and the long-term prognosis is equally difficult to predict, the results of surgical procedures and nonoperative treatment alike are open to question.20
X-Rays. The astute physician should carefully examine the knee series. The standard radiographs are often normal or may simply demonstrate an intra-articular effusion. A small avulsion fracture of the lateral tibial condyle just below the joint line is a sign of an ACL tear. This is often called the "lateral capsular sign."21
MRI may be required for an accurate diagnosis. With the advent of noninvasive MRI studies, arthroscopy is now employed less often. MRI may show concomitant subchondral bone lesions (fractures or bruises) with ACL injuries.22
Treatment. Treatment of the isolated ACL injury is both individualized and controversial.17,23 There is no convincing study demonstrating that immediate surgery is essential to long-term usefulness and decreased morbidity. Both conservative non-operative approaches and operative approaches are currently recommended by significant numbers of physicians who claim advantages for their therapy.
Consider the acuteness of injury, age, instability, degree, type of injury to the ACL, ability to rehabilitate, and, most importantly, the desired level of future activity in recommending one or the other therapy. Early surgical intervention is favored in athletes who desire to return to sports that place high functional demands on the knee.24 The patient who has a positive pivot-shift examination is likely to develop functional instability and require surgical repair.3
If the patient has a tense, painful hemarthrosis, it may be aspirated and the patient placed in a knee immobilizer or other splinting device. Aspiration of the hemarthrosis will provide both a significant clue to the diagnosis and substantial pain relief for the patient. This should be followed by ice to the area, adequate pain management, and expeditious orthopedic referral.
Complications. Complications of ACL injuries include knee dislocation and functional loss that produces abnormal knee motions and major degenerative changes.
Posterior Cruciate Ligament Sprain. Mechanisms of Injury. The posterior cruciate ligament is rarely injured alone. Sports-related trauma and motor vehicle accidents (MVAs) are the most common causes of injury to the posterior cruciate ligament, but these injuries are often associated with simultaneous injuries to other ligaments in the knee. Isolated injuries to the posterior cruciate can occur with a fall on a flexed knee or a dashboard injury to the flexed knee.25 (See Table 3.) Hyperextension of the knee tears the posterior cruciate ligament only after the ACL has been destroyed. The resultant dislocation of the knee may be reduced by the time that the patient presents to the ED. A severe varus or valgus bending movement of the knee will injure the posterior cruciate ligament together with the anterior cruciate and or the collateral ligaments. A "clipping" injury can disrupt the posterior-lateral structures, including the posterior-cruciate ligament.
Symptoms and Signs. Abrasions, lacerations, or ecchymosis about the tibial tubercle should invoke suspicion of a posterior cruciate injury. The patient may walk with a slightly flexed knee to avoid a terminal extension of the knee. A thorough neurovascular examination and consideration of the possibility of an acute popliteal artery injury are essential if this injury is found, since the patient may have had a dislocation of the knee that has been reduced in the field.
The most accurate assessment of the posterior cruciate ligament is either the posterior drawer test in 90° of flexion or the reverse pivot-shift test. The posterior drawer test is performed exactly like the anterior drawer test except that the tibia is pushed posteriorly instead of pulling on it. Some authors also feel that the test should be performed at 45° to increase the sensitivity of the examination.26
Insall and Hood described the posterior sag sign associated with posterior cruciate ligament injuries. If the patient is supine and the knee is flexed 90°, the tibia will sag into posterior subluxation if the patient has a complete tear of the posterior cruciate ligament.27
The diagnosis can be confirmed by MRI. This test is essentially 100% specific and sensitive in the diagnosis of an acute posterior cruciate ligament injury.22 There may be some chronic injuries of the posterior cruciate ligament that are not noted on MRI.
Treatment. Treatment of the isolated tear of the posterior cruciate ligament is under debate. Since the posterior-cruciate ligament is often not damaged alone, orthopedic literature has focused on these combined injuries. Some authors feel that patients with slight-to-moderate posterior instability are often able to compensate adequately with good quadriceps function.26 Others feel that there is substantial long-term disability associated with isolated injuries of the posterior cruciate ligament; and these orthopedic surgeons are re-thinking the non-operative treatment currently rendered.25
If the patient has a posterior cruciate ligament injury combined with other ligament injuries, then the patient should be suspected of having a dislocation of the knee that has been reduced in the field. This patient should be treated as if he or she has had a dislocation, and the neurovascular status should be carefully evaluated by frequent examinations or arteriogram.28
Collateral Ligament Tears. Incidence. Collateral ligament strains and sprains are common. The vast majority of collateral ligament injuries result from sports. Although contact sports such as soccer and football are most often implicated, skiing is an important cause of knee injuries.29 In a study of 160 knee injuries in athletes, 12% were collateral ligament tears, and all but one occurred on the medial side. 30
Mechanisms of Injury. The patient with a collateral ligament injury usually has trauma to the contralateral side of the knee or has had excessive forces applied to the knee in a valgus or varus direction. (See Table 3.) The skier may have the ski rotate without a binding release or with the boot catching in the snow after the binding releases. Combined injuries of the ACL and the MCL are common.
Symptoms and Signs. The patient may report a tearing sensation and immediate pain at the time of the injury. The amount of swelling and ecchymosis depends on the severity of the injury. If the capsular portion of the medial collateral ligament is torn, or if the patient has a concomitant cruciate injury, then a hemarthrosis may be found. Complete capsular disruption may allow blood to extravasate into the tissues.
The patient is usually tender about the distal femur at the femoral condyle and extending to the joint line because the injury most often involves the proximal portion of the MCL. If the patient is tender about the medial side of the patella, then look for a tear of the medial retinaculum.
Since lateral collateral ligament injuries are uncommon, they may be missed. When there is lateral collateral tenderness, swelling, or ecchymosis, the examiner must carefully elicit the mechanism of injury in order to ensure that the lateral collateral ligament is not involved. MCL injuries cause joint instability more frequently than do lateral collateral ligament injuries. The wider, lateral collateral ligament is most often partially torn; hence, no instability is found.
Treatment. The treatment for a grade I or grade II collateral sprain is ice to the area, compression, elevation, and rest. (See Table 4.) A non-steroidal anti-inflammatory medication may both relieve pain and decrease swelling. A knee brace for 4-6 weeks will decrease the chance of a re-injury.
Treatment of a grade III injury is somewhat controversial. Most orthopedic surgeons favor nonoperative therapy and short-term immobilization. The knee should be adequately braced during the rehabilitation. Prospective studies show no benefit from surgical management, but some orthopedic surgeons still feel that a surgical repair is indicated in these cases.31,32
The menisci are semilunar fibrous cartilages in the capsule of the knee joint. In cross-section, the meniscus is triangular in shape, with the apex of the triangle directed central and the base of the triangle at the joint margin. They act as shock absorbers, provide lubrication, and more evenly distribute weight to the femoral condyles and the tibial plateau. They also act as spacers to increase the stability of the knee. The medial meniscus is attached to the capsular portion of the MCL. If the MCL is damaged, then the medial meniscus may also be disrupted. The attachments of the lateral meniscus have the popliteal tendon passing through them posteriorly and laterally. Like the lateral collateral tendon, the lateral meniscus is less frequently damaged than the medial meniscus.
The peripheral portion of the meniscus is vascular, while the central portion of the meniscus is relatively avascular. Both menisci receive their entire blood supply from their peripheral attachments, so a torn meniscus may become avascular and degenerate rapidly. The medial avascular portion of the meniscus does not heal well, even if repaired.
The majority of patients with a meniscus tear are in their 20s.33 Because the meniscus has such important functions in load bearing and stability of the knee, a loss of this structure in the young athlete is associated with significant degenerative changes. When the meniscus is removed or becomes avascular and degenerates, the mechanics of the knee will change.34 The articular surface contact forces rise 2-3 times, and substantial degenerative changes in the contact surfaces of the joint result.
The two meniscal cartilages are easily injured, often with seemingly trivial trauma.35 The menisci can be injured as a result of twisting, hyperflexion of the knee, and rotatory instability of the knee. Patients may note that they planted the foot and twisted the knee or fell on the hyperflexed knee. This combination is often found in the martial arts.
There is no generally accepted classification of meniscal tears. They can be classified by shape, position in relation to the anterior or posterior "horn" of the meniscus, and by whether or not they have been displaced from the normal position. They can also be graded by whether or not they occur due to trauma, degeneration, or are in association with ligamentous knee instability. The most common types of meniscal tear are the "bucket handle" tear and a flap tear, where one end of the "bucket" handle has been torn free. These are both vertical lesions that occur following injuries, and are often displaced. Medial tears are more common than lateral tears. Medial bucket-handle tears may be associated with a chronic ACL tear.
When they are torn, meniscal injuries frequently present with a clear effusion and delayed swelling. The patient often notes swelling the day after the injury. If the meniscus is torn in the vascular peripheral third of the meniscus, the effusion may be both bloody and immediate. However, the acuity of the hemarthrosis is of limited help in differentiating meniscal from ligamentous injuries. Occasionally, the patient may complain that the knee "locks." Later in the course, the patient may note pain during activity (turning and pivoting) and morning stiffness.
The examiner may note tenderness in the medial or lateral joint line. This may be the most predictive clinical finding of meniscal injury.36 If the tear is posterior, then hyperflexion of the knee will increase the pain. Likewise, hyperextension of the knee will be painful if the tear is anterior. A spongy block to full knee extension may be noted when the patient has a displaced bucket-handle tear that is in the intercondylar notch. A chronic injury may be accompanied by visible quadriceps atrophy or may be documented by measuring thigh circumference about one hand-breath above the patella in both thighs.
Definitive diagnosis of a meniscal tear may be made with arthroscopy or MRI. Arthroscopy has the advantage of simultaneous repair if indicated, while MRI is completely non-invasive.
Meniscus tears may be managed nonoperatively, by meniscectomy (both open and by arthroscopy), and by repair of the meniscus by various means.37 In general, the smaller tears, or those that are only partial thickness, may best be managed by leaving them alone. Meniscectomy, by either arthroscopy or open surgery, still causes significant long-term disability in many cases, beginning after only a few years.38,39 Disability is markedly reduced if the repair is done within two months of the injury.33
Distal Femur Fractures. Fractures of the distal femur are usually caused by axial loading combined with varus or valgus stress and rotation. They may be classified as supracondylar, intercondylar, or condylar fractures.
Supracondylar fractures are often transverse or slightly oblique, with varying degrees of displacement and/or comminution of the fracture fragments. Like all fractures, they may be open or closed. If there is a posterior component, the popliteal artery may be involved. If there is sufficient force, then the patient may have also sustained damage to the four major ligaments at the same time. Some supracondylar fractures can extend into the knee to form an intercondylar fracture.
Condylar fractures result from varus or valgus force. These fractures are more difficult to detect on routine radiographs. MRI or CT scan may demonstrate the fracture site. In children and adolescents, the attachment of the adductor muscle group may be avulsed, leaving a cortical irregularity.
Proximal Tibia Fractures. Mechanism. Mechanisms that can cause a tibial plateau fracture include axial loading (fall from a height), varus or valgus forces, and/or rotation. Sports that can cause these injuries include football, soccer, rugby, hang gliding, gymnastics, and sport parachuting. Common features of these fractures include a very stable fracture and intact ligaments of the knee.
Violent, twisting movements or abduction-adduction injuries can cause fractures of the tibial spine or the intercondylar eminence. These injuries are often combined with significant soft-tissue and ligamentous lesions and may be classified as a "fracture dislocation" of the knee. Needless to say, these injuries may also cause simultaneous arterial or nerve damage.
Signs and Symptoms. Signs and symptoms include tenderness and swelling over the fracture site, instability of the knee with stress testing, and the inability to bear weight.
Diagnosis. Intra-articular fractures of the proximal tibial plateau may be quite subtle. In addition to the conventional radiographic series of the knee, computerized tomography may be required for diagnosis. The films should be carefully examined for disruption of the articular surface, effusions, and avulsion fractures at the sites of ligamentous attachments in the femoral condyles, fibular head, and intercondylar eminence. Tibial plateau fractures should be suspected in the presence of localized bony tenderness, effusion, and pain with axial loading.
Treatment. Conservative treatment with long-leg splinting is appropriate unless the fracture is depressed or displaced by more than a centimeter. These fractures may require operative reduction with internal fixation (ORIF) if the fragments are widely separated or depressed. If there is a depressed fragment in an area of weight bearing, then operative intervention may be indicated.
Deep vein thrombosis is a common complication in tibial plateau fractures.40 Doppler studies are indicated in these patients at the slightest suspicion of DVT.
Complex trauma involving the proximal tibia may also cause compartment syndrome. If there is any suspicion that the patient has a compartment syndrome, then compartmental pressures should be measured promptly.
Fibular Fractures. The fibula is rarely fractured in isolation. These injuries may result from direct trauma to the head or neck of the fibula (bumper injuries), varus forces that avulse a fragment of the proximal pole or styloid process of the fibula, valgus forces that also produce lateral tibial plateau fractures or medial collateral ligament injuries, or twisting injuries at the ankle with pronation and external rotation. Detection of a fracture of the fibula should prompt evaluation of the ankle or a simultaneous ligamentous injury.
The fibular fracture may be accompanied by rupture of the lateral capsule and ligamentous structures and stretching of the peroneal nerve. Other complications of the proximal fibular fracture include arterial injury to the nearby anterior tibial artery or contusion of the biceps tendon.
Fractured Patella. Mechanism. Fractures of the patella are caused by either direct trauma or indirect forces caused by forcible quadriceps tendon contraction. Direct trauma is the most common mechanism of injury. Unilateral injuries are very common, but some bilateral fractures occur. There is a 2:1 predominance in males over all age groups. About 50-80% of patellar fractures are transverse.41 Longitudinal (25%) or stellate fractures (20-35%) usually result from direct trauma, such as "dashboard knee."42 Patellar fractures caused by quadriceps traction may break the bone into equal-sized components or avulse either pole of the patella. Fractures of the inferior portion of the patella are more common.
The most important clinical feature is whether the patient can actively raise the leg off the bed in full extension. Any injury causing complete disruption of the extensor mechanism, including fracture of the pelvis and the surrounding retinaculum, will prevent this motion.
Severely comminuted fractures may require surgical removal of the patella, as degenerative arthritis is found in 39% of the cases.43 Fractures that are so disrupted that the leg cannot be raised require surgical repair of the patella for functioning of the quadriceps tendon.
Signs and Symptoms. The examiner may find tenderness and swelling over the patella or an inability to extend the knee. If the extensor mechanism is disrupted, the patient may be able to stand but not walk with a normal gait. Walking may be accomplished by leaning forward over the injured leg and allowing gravity to drop the leg. A palpable defect or a bloody joint effusion may also be noted.
X-Ray. Most patellar fractures are readily apparent in normal overhead radiographs. Be sure to get the sunrise (axial/skyline) view to ensure an adequate view of the patella if standard views are nondiagnostic in the setting of strong clinical suspicion.
Treatment. If the fragments are displaced more than 4 mm, or if the patient is unable to raise the extended leg off of the bed, then operative intervention is needed. If there is no displacement, then a long-leg cylinder cast or knee immobilizer is appropriate. Unless there is a complication requiring immediate intervention, orthopedic referral can be in the office over the next few days.
Traumatic dislocation of the knee (referring to the tibia and femur) is rare.44 It requires violent trauma to dislocate the knee, and even large teaching institutions see only a few of the these serious injuries in a year. If it is not properly and promptly managed, significant long-term disability or loss of the limb can result.45
Complete dislocation of the knee is caused by direct or indirect violence. Dislocations may be classified as anterior, posterior, lateral, medial, or rotatory. The type of dislocation will depend on the direction and location of the forces applied. Since a severe force is required to dislocate the knee, most are caused by automobile accidents, car vs. pedestrian accidents, motorcycle injuries, and contact sports.46 Motor vehicle accidents are the most common cause, with athletic injuries being a distant second.
Hyperextension of the Knee. Anterior knee dislocations are produced by hyperextension. As the knee is hyperextended, the posterior capsule ruptures at about 30°. The anterior and posterior cruciate ligaments follow shortly thereafter.47 When the posterior cruciate ligament ruptures, the tibia rides forward on the femur, producing the anterior dislocation. As the hyperextension continues, the popliteal artery is stretched, and then ruptured, at about 50°. These figures were measured in cadavers, but less hyperextension was thought to be needed for the same injury in living subjects.48
Medial, Lateral, and Posterior Dislocations. Medial, lateral, and posterior dislocations are much more difficult to produce experimentally. The experimental procedures used to produce them cause tibial plateau and supercondylar fractures more frequently than they dislocate the knee.46 This is the same pattern found in clinical practice. These dislocations are usually caused by extreme direct violence applied to the lower end of the femur with a fixed tibia, or the upper end of the tibia when the femur has been fixed in place. Medial dislocation tears the cruciate and lateral ligaments. Lateral dislocation tears the medial and cruciate ligaments. Posterior dislocation is caused by a direct force to the proximal anterior tibia.49
Rotary dislocations are caused by a rotation of the foot about the knee. The most common rotatory dislocation is the posterolateral dislocation. Surgical reduction may be required if closed reduction fails.
Signs and Symptoms. Unfortunately, evaluation of the traumatic dislocation may not reveal any deformity.46 Frequently, either spontaneous reduction or reduction at the scene by trainers or EMS providers occurs. If severe ligamentous injury is found in the knee and there is a compatible mechanism recounted by patient or spectators, then a reduced dislocation should be suspected. A knee with a torn ACL, posterior cruciate ligament, and a collateral ligament tear on one side should be considered a dislocation that has been reduced.50 Dislocations of the knee that cannot be easily reduced in the ED are quite rare indeed.51
A detailed assessment of the lower extremity and knee, including evaluation for signs of compartment syndrome, is vitally important. Particular attention should be directed to the distal pulses, the sensation of the great toe and first web space, the ability to move the toes, and examination of the knee. Swelling, coolness, lack of distal pulses, distal skin coolness, or decreased sensation should prompt rapid evaluation of the patient’s arterial supply to the lower leg.
Since it is difficult to differentiate between neural and vascular injury in the lower extremity, evaluation of the blood supply with an angiogram is almost always needed. If the patient develops a gradual loss of sensation over the digits, then critical ischemia may be present. An obvious temperature difference between the two feet should strongly suggest an arterial occlusion. If the pulses are absent, then immediate evaluation and treatment is imperative.
Complications. Open Dislocations. Dislocations may also be open or closed. A less favorable prognosis is found in open dislocations, but this may be because there is extensive soft-tissue damage and associated injuries in many of these cases.
Popliteal Artery Injury. The blood supply to the foot and leg is very dependent on the popliteal artery, and very little collateral circulation exists. Damage to the popliteal artery is the single most devastating complication of traumatic dislocation of the knee. It occurs in about 40% of all knee dislocations.52 Collateral circulation around the knee is clearly inadequate to supply the foot and lower distal leg, and the extremity will be ischemic if the popliteal artery is damaged. If it is not treated promptly and adequately, then the patient will require amputation of the lower extremity more than 90% of the time.52
An arteriogram should be obtained if there is even the remotest suspicion of vascular injury or if there is any neurologic injury. This procedure cannot wait, since the blood vessel must be repaired within 6-8 hours to maintain viability of the extremity. A good rule of thumb is that the patient needs an arteriogram if three out of four ligaments are torn.
Peroneal and Tibial Nerve Injury. Fortunately, nerve injuries associated with dislocation of the knee are less frequent than vascular injuries. The tibial and common peroneal nerves are less prone to injury because they are not as firmly attached to the structures in the back of the knee. When injury occurs, there is often extensive longitudinal damage from the traction on the nerves. Peroneal nerve injury has a poor prognosis. There appears to be no help from any operative procedure. If the patient has signs of peroneal nerve injury, an arteriogram is needed to discover any concomitant or causative vascular injury.
Treatment. The dislocated knee must be reduced promptly. If there is any vascular compromise, immediate reduction prior to radiographs is indicated. The knee is reduced by longitudinal traction, while simultaneously lifting the femur into place. Avoid pressure in the popliteal fossa during reduction. Have an assistant provide counter-traction by holding onto the shoulders or hips. Simple traction and counter-traction will usually suffice for reduction and provide significant pain relief. Supplemental intravenous pain medication is generally needed, however. Following reduction, a posterior leg splint should be placed at 15° flexion to avoid stretching the popliteal artery. An arteriogram to evaluate the popliteal artery should then be obtained. Surgery will be needed if there is an open fracture, if the dislocation cannot be reduced, or if there is evidence of popliteal artery injury.
Mechanism. Dislocation of the patella is quite common. Lateral dislocation is most common and may be caused by flexion, external rotation, and simultaneous contraction of the quadriceps tendon. Quadriceps contraction pulls the patella lateral during push off or step. Direct trauma may also cause a dislocation. Dislocations are unlikely if the patient has normal patello-femoral anatomy.
Signs and Symptoms. Clinically, the patient will have an obvious lateral deformity and swelling. If spontaneous reduction occurs, tenderness on medial patellar and lateral femoral-line palpation can be noted.
If recurrent dislocation is suspected, check the "apprehension" test. Ask the patient to lie supine on the examination table with legs flat and the quadriceps relaxed. Press against the medial border of the patella. The patient will start to show apprehension and distress. In addition, the underside of the patella may be tender.
Complications. Osteochondral fracture with intra-articular fragments may be present and cause degenerative arthritis. This is more common when the patella is dislocated by direct trauma. Since 28-50% of patients with patellar dislocation have an associated fracture, radiographs of the patella are needed even when the dislocation has been reduced.53,54
The patient may develop a hemarthrosis following dislocation of the patella. Aspiration of the joint may be needed if reduction is obstructed by the hemarthrosis.
Recurrent dislocation is a significant problem. The younger the patient is at the time of the initial injury, the more likely a recurrent dislocation becomes.54 Recurrence of dislocation may be lessened by strengthening of the vastus medialis, oblique, and gluteus muscles.
Treatment. Treatment includes immediate reduction of the patella by simply extending the knee and moving the patella medially. The patient will be more comfortable if a hemarthrosis is aspirated when present. The patient may be treated with either a cylinder cast or a knee immobilizer with follow up in the consultant’s office. Recurrent dislocations or fractures that are associated with dislocations may require an operation.
Quadriceps and Patellar Tendon Rupture. Rupture of the quadriceps tendon is relatively uncommon.55 Like the disruption of the patella associated with a patellar fracture, the patient is unable to maintain the knee in full extension against gravity. The patient will be unable to climb stairs or to walk up an incline. A palpable soft-tissue defect may be found above the patella proximal to the superior pole of the patella. A complete rupture is usually found, but partial ruptures may also be found.
Quadriceps tendon rupture can present in a deceptively mild fashion. About half of patients are initially misdiagnosed. The patient may have little swelling and pain and is simply unable to raise the leg against gravity. If the patient is not asked to perform a straight-leg raise or to walk, the patient’s problem may be missed. If the patient is treated with a knee immobilizer, then he or she is able to walk because the immobilizer takes the place of the torn quadriceps tendon.56
Radiographs may occasionally show an avulsion chip fracture, but are most often normal. Quadriceps rupture may be noted on ultrasound or MRI, but neither is usually ordered from the ED.
Treatment of rupture of the quadriceps tendon is usually early surgical repair. Following repair of the tear, the patient is treated with cast immobilization. Most patients regain full function of the knee. If the treatment is delayed, then the quadriceps tendon will retract and atrophy, making successful reapproximation of the ends more difficult.57
Rupture of the patellar tendon is less common than either fracture of the patella or rupture of the quadriceps tendon. It is more often seen in basketball and volleyball players, who have repetitive violent contraction of the quadriceps muscles.58 An abnormally high position of the patella may be helpful in diagnosis. A knee radiograph may show an avulsion of the tibial tubercle and displacement of the patella superiorly.
The emergency physician is often the initial health care provider evaluating patients with acute knee injuries. Using basic examination techniques and selected imaging studies, identification of specific diagnoses may be possible. Many serious injuries may not be able to be diagnosed acutely; however, careful evaluation will generate appropriate suspicion and should result in early orthopedic referral such that optimal long-term management and surgical repair, as indicated, result.
References
1. Dehaven K, Litner DM. Athletic injuries: Comparison by age, sport, and gender. Am J Sports Med 1986;14:218-224.
2. Tubbs N. Injured ligaments of the knee. Injury 1990;21:291-293.
3. Gersoff WK, Clancy WG Jr. Diagnosis of acute and chronic anterior cruciate ligament tears. Clin Sports Med 1988;7:727-738.
4. Lombardo JA. The athlete’s knee: An orderly examination. Emerg Med 1984;16:34.
5. Baker CL. Acute hemarthrosis of the knee. J Med Assoc Georgia 1992;81:301-305.
6. Daniel DM, Malcom LL, Losse G, et al. Instrumented measurement of anterior laxity of the knee. J Bone Joint Surg 1985;67A:720-726.
7. King JB, Aitken M. Treatment of the torn anterior cruciate ligament. Sports Med 1988;5:203-208.
8. Stiell IG, et al. Derivation of a decision rule for the use of radiography in acute knee injuries. Ann Emerg Med 1995;26:405-413.
9. Weber JE, et al. Clinical decision rules discriminate between fractures and non-fractures in acute isolated knee trauma. Ann Emerg Med 1995;26:429-433.
10. Bauer SJ, Hollander Je, Fuchs SH, et al. A clinical decision rule in the evaluation of acute knee injuries. J Emerg Med 1995;13:611-615.
11. Stiell IC, Greenberg GH, Wells GA, et al. Prospective validation of a decision rule for the use of radiography in acute knee injuries. JAMA 1996;275:611-615.
12. Herzog RJ. Imaging of the knee. Orthop Rev 1992:21:421-424.
13. Mink JH, Deutsch AL. Magnetic resonance imaging of the knee. Clin Orthop and Rel Res 1989;244:29-47.
14. Yu JS, Petersilge C, Sartoris D, et al. MR imaging of the injuries of the extensor mechanism of the knee. Radiographics 1994;14:541-551.
15. Ekstrom JE. Arthrography: Where does it fit in? Clin Sports Med 1990;9:561-566.
16. Sonnaben DH, Collican MRJ. Recent advances in arthroscopy. Aust Fam Pract 1993;21:421-424.
17. King JB. Focal points in orthopaedics. Br Med Bull 1992;48:651-667.
18. Swenson TM, Hamer CD. Knee ligament and meiscal injuries. Orthop Clin North Am 1995;26:529-546.
19. Perko MMJ, Cross MJ, Ruske D, et al. Anterior cruciate ligament injuries: Clues for diagnosis. Med J Aust 1992;157:467-470.
20. Daniel DM, Fithian DC. Indications for ACL surgery. Arthroscopy 1994;10:434-441.
21. Woods GW, Stanley RF, Tullos HS. Lateral capsular sign: X-ray clue to a significant knee instability. Am J Sports Med 1979;7:29-33.
22. Fowler PJ. Bone injuries associated with anterior cruciate ligament disruption. Arthroscopy 1994;10:453-460.
23. Noyes FR, McGinnis GH. Controversy about treatment of the knee with anterior cruciate laxity. Clin Orthop 1985;198:61-76.
24. Gooch JI, Geiringer SR, Akau CK. Sports medicine. 3: Lower extremity injuries. Arch Phys Med Rehabil 1993;74:S438-S442.
25. Covey DC, Sapega AA. Current concepts review: Injuries of the posterior cruciate ligament. J Bone Joint Surg 1993;75A:1376-1384.
26. Whipple TL, Ellis FD. Posterior cruciate ligament injuries. Clin Sports Med 1991;1:515-527.
27. Insall JN, Hood RW. Bone-block transfer of the medial head of the gastrocnemius for posterior cruciate insufficiency. J Bone Joint Surg 1982;64A:691-699.
28. Bratt HD, Newman AP. Complete dislocation of the knee without disruption of both cruciate ligaments. J Trauma 1993;34:383-389.
29. Steadman JR, Sterett WI. The surgical treatment of knee injuries in skiers. Med Sci Sports Exerc 1995;27:328-333.
30. Jensen JE, Conn RR, Hazelrigg G, et al. Systematic evaluation of acute knee injuries. Clin Sports Med 1985;4:295-312.
31. Indelicato PA. Non-operative management of complete tears of the medial collateral ligament of the knee. J Bone Joint Surg Am 1983;65:323-329.
32. Smith BW, Green GA. Acute knee injuries part II. Diagnosis and management. Am Fam Phys 1995;51:799-806.
33. Henning CE. Current status of meniscus salvage. Clin Sports Med 1990;9:567-576.
34. Renstrom P, Johnson RJ. Anatomy and biomechanics of the menisci. Clin Sports Med 1990;9:523-538.
35. Hardin GT, Farr J, Bach BR. Meniscal tears: Diagnosis, evaluation, and treatment. Orthopedic Rev 1992;21:1311-1317.
36. Hede A. Treatment of meniscal lesions in the knee. Dan Med Bull 1993;40:317-331.
37. Muckle DS. Meniscal repair in athletes. Sports Med 1988;5:1-5.
38. Henning CE. Semilunar cartilage of the knee: Function and pathology. Exer Sport Sci Rev 1988;16:205-213.
39. DeHaven KE, Sebastianelli WJ. Open meniscus repair: Indications, technique, and results. Clin Sports Med 1990;9:577-586.
40. Tscherne H, Lobenhoffer P. Tibial plateau fractures: Management and expected results. Clin Orthop Rel Res 1993;292:87-100.
41. Calkins C, Sartoris DJ. Imaging acute knee injuries. Phys in Sports Med 1992;20:91-99.
42. Duncan GF, Meals R. One hundred years of automobile induced orthopedic injuries. Orthopedics 1995;18:167-170.
43. Crenshaw AH, Wilson FD. The surgical treatment of fractures of the patella. South Med J 1954:47:716.
44. Hoover NW. Injuries of the popliteal artery associated with fractures and dislocations. Surg Clin North Am 1961;41:1099-1112.
45. Kremchek TE, Welling, RE, Kremchek EJ. Traumatic dislocation of the knee. Orthop Rev 1989;18:1051-1057.
46. Roman PD, Hopson CN, Zenni EJ. Traumatic dislocation of the knee: A report of 30 cases and literature review. Orthop Rev 1987;16:917-924.
47. Girgis M. The cruciate ligaments of the knee joint. Clin Orthop 1975;106:216-231.
48. Kennedy J. Complete dislocation of the knee joint. J Bone Joint Surg 1963;45A:889-904.
49. Taylor AR, Arden GP, Rainey HA. Traumatic dislocation of the knee: A report of 43 cases with special reference to conservative treatment. J Bone Joint Surg 1972;54B:96-102.
50. Merrill KD. Knee dislocations with vascular injuries. Orthop Clin North Am 1994;25:707-173.
51. Nystrom M, Samimi S, HaEri GB. Two cases of irreducible knee dislocation occurring simultaneously in two patients and a review of the literature. Clin Orthop Rel Res 1992;277:197-200.
52. Green A. Vascular injuries associated with dislocation of the knee. J Bone Joint Surg 1977;59A:236-239.
53. Garrick JG. Knee problems in adolescents. Pediatr Rev 1983;4:235-243.
54. Cash JD, Hugston JC. Treatment of acute patellar dislocation. Am J Sports Med 1988;16:244-249.
55. Ramsey RH, Muller GE. Quadriceps tendon rupture: A diagnostic trap. Clin Orthop Rel Res 1970;70:161.
56. Roberts J. Quadriceps tendon rupture. Emerg Med News 1993;July:14-16.
57. Siwek CW, Rao JP. Ruptures of the extensor mechanism of the knee joint. Am J Bone Joint Surg 1981;63:932-937.
58. Nance EP, Kaye JJ. Injuries of the quadriceps mechanism. Radiology 1982;142:301-307.
Physician CME Questions
1. When examining the patient with a knee injury, the most appropriate position is:
A. supine.
B. sitting up.
C. hanging the leg off of the side of the bed.
2. Palpation of the knee may reveal all of the following except:
A. tear of the medial collateral ligament
B. tear of the lateral collateral ligament
C. tear of the patellar tendon
D. tear of the posterior cruciate ligament
3. The most commonly injured ligament of the knee is the:
A. lateral collateral ligament.
B. posterior cruciate ligament.
C. medial collateral ligament.
D. anterior cruciate ligament.
4. Which of the following injuries is least painful?
A. Medial collateral tear
B. Anterior cruciate tear
C. Dislocation of the patella
5. Which of the following tests is most appropriate for diagnosis of the anterior cruciate ligament tear?
A. Reverse pivot-shift test
B. Lachman’s test
C. Murphy’s test
6. Which of the following tests is most appropriate for diagnosis of tears of the medial collateral ligament?
A. Reverse pivot shift test
B. Lachman’s test
C. Direct palpation of the joint
7. What is the most important complication of fracture of the patella?
A. Distraction of the fracture fragments
B. Hemarthrosis
C. Joint instability
D. Comminution of the fragments
8. The most important complication of dislocation of the knee is:
A. instability of the joint.
B. inability to bear weight.
C. inability to reduce the joint.
D. arterial injury.
You have reached your article limit for the month. Subscribe now to access this article plus other member-only content.
- Award-winning Medical Content
- Latest Advances & Development in Medicine
- Unbiased Content