Effect of shoulder tightness on glenohumeral translation, scapular kinematics, and scapulohumeral rhythm in subjects with stiff shoulders.

Shoulder tightness may cause altered kinematics and lead to development of subacromial impingement, tendinitis, and degenerative changes. In this investigation, the humeral head translations, scapular kinematics, and scapulohumeral rhythm were determined with a three-dimensional electromagnetic tracking device during arm elevations in six subjects with anterior shoulder tightness and in six subjects with posterior shoulder tightness to study the effects of anterior/posterior tightness on shoulder kinematics. Subjects with anterior tightness showed lower slopes in curves of glenohumeral elevation plotted against scapular upward rotation (scapulohumeral rhythm, 0.11 to 0.32; p = 0.021) and less posterior scapular tilt (2.9 to 7.5 degrees; p = 0.002) during arm elevations when compared to the group with posterior tightness. The humeral head was positioned less posteriorly (2.2 to 3.4 mm; p = 0.004) and more superiorly (3.8 to 7.0 mm; p < 0.0005) during arm elevation in subjects with posterior tightness. The alternations in shoulder kinematics between subjects with anterior and posterior shoulder tightness may be relevant to the development of subacromial impingement, tendinitis, and degenerative changes as seen in subjects with stiff shoulders.