Glenohumeral Joint Laxity and Stiffness in Healthy Men and Women
Abstract & Commentary
Synopsis: Shoulder arthrometry finds differences in glenohumeral joint laxity and stiffness in males and females.
Source: Borsa PA, et al. Patterns of glenohumeral joint laxity and stiffness in healthy men and women. Med Sci Sports Exerc 2000;32(10):1685-1690.
Borsa and colleagues used a shoulder arthrometer to measure glenohumeral joint laxity and stiffness in 51 physically active and healthy men and women. The subjects were free from history of shoulder injury and had not participated in regular physical activity involving upper-extremity overhead throwing motions. Prior to participation in the study, each subject was screened by an orthopaedic surgeon for hyperlaxity and pathology involving joint instability. No subjects had greater than 1+ laxity of the glenohumeral joint in any direction.
Joint laxity was defined as the amount of humeral head translation from the glenoid in response to 67, 89, 111, and 134 N of force. Joint stiffness was measured as the slope of the force-displacement curve using least squares regression. The instrumented arthrometer applied force to the glenohumeral joint using a custom applicator. Two linear displacement transducers individually measured linear motion of the humeral head and the acromion. Subjects were seated and secured in a test chair, with the humerus positioned and secured in 20° of abduction and neutral rotation, flexion, and extension. Generalized joint hypermobility was also measured with a standard plastic goniometer. For all measurements, both shoulders were tested in random order.
The women were found to have more anterior joint laxity than men (11.4 vs 8.3 mm), and the men had more posterior than anterior joint laxity (9.6 vs 8.3 mm). The women had less anterior joint stiffness than the men (16.3 vs 20.5 N/mm), and the women had less anterior than posterior stiffness (16.3 vs 22.1 N/mm). The women also had more generalized joint hypermobility than the men (2.9 vs 1.0°).
Comment by David H. Perrin, PhD, ATC
Joint arthrometry is commonly used to assess anterior and posterior laxity of the knee (tibio-femoral) joint and compliance of the ACL. These assessments are undertaken for purposes of pre-season screening of athletes, to aid in diagnosis of injury to the cruciate ligaments, and to assess the success of surgical reconstruction. Borsa et al have developed a model that permits easy assessment of anterior and posterior glenohumeral joint displacement. From these measures, one can determine not only absolute values of laxity but can calculate joint stiffness as well. Borsa et al previously reported on the reliability of the device,1 and now they provide us with baseline comparative values for males and females.
It is interesting that the glenohumeral joint laxity and stiffness findings in males and females are relatively consistent with values reported for the knee. It would be interesting to determine if laxity of the shoulder reacts the same as the knee in response to training and the influence of female hormones. It will also be interesting to determine through prospective longitudinal studies if the increased anterior laxity and decreased joint stiffness in females predispose them to joint instability and injury. As with knee arthrometry, a practical method of assessing glenohumeral joint laxity and stiffness has endless potential for advancing our understanding of this complex joint in both athletes and nonathletes.
Reference
1. Borsa PA, et al. In vivo assessment of AP laxity in healthy shoulders using an instrumented arthrometer. Journal of Sport Rehabilitation 1999;8:157-170.
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