PHYSIOLOGY JOINT PHYSIOLOGY ➢ Scapulohumeral joint This joint can achieve : ❉ Movements following a transverse axis passing through the center of the humeral head and parallel to the plane of the scapula: . ● The flexion movement (antepulsion) is carried out by the coraco-brachialis, the fasciculus anterior of the deltoid, the short portion of the biceps, the superior bundleof the pectoralis major. It is stopped by tension of the coracohumeral ligament. Itsmaximum amplitude is °, the scapulo-humeral is sufficient for its realization, beyondthis angle there is an internal rotation of the scapula. . ● The extension movement (retropulsion) is caused by the contraction of the large teres, teres minor and posterior fascicles of the deltoid. If the retropulsion isprolonged the rhomboids, the latissimus dorsi and the trapezius participate in themovement. Extension is stopped by tension of the coracohumeral ligament. Itsmaximum amplitude is ° .Movements carried out around an antero-posterior axispassing through the center of the humeral head and perpendicular to the plane of thescapula. . ● The abduction movement is caused by the simultaneous contraction of the deltoid which is the only active abductor and the supraspinatus whose role is to press thehumeral head against the glenoid cavity and thus prevent its elevation. This lattermechanism is reinforced by the capsuloligamentous vault. The movement is limitedby the contact of the greater tuberosity against the glenoid cavity (0°), then by themobility of the scapula. Its maximum amplitude is °. Up to 0° only the glenohumeraljoint participates in the movement. Beyond this value, rotation of the scapula isessential. . ● The adduction movement is caused by the contraction of the pectoralis major, latissimus dorsi and subscapularis. This is a movement most often performed duringpull-ups, that is to say when the arm is already in abduction. Its maximum amplitudeis a few degrees. Adduction is limited by the meeting of the arm with the trunk. ❉ Movements made around an axis passing through the center of the humeral head and parallel to that of the body. . External rotation is caused by the infraspinatus and teres minor. Its amplitude maximum is °.External rotation is limited by the tension of the joint capsule and the internal rotatormuscles. . Internal rotation is caused by contraction of the subscapularis, major pectoral,teres major and latissimus dorsi. Its maximum amplitude is 0°. It is limited by the tension ofthe capsule and the external rotators. ❉ Complex movements integrating abduction/adduction and flexion/extension
This type of movement, called circumduction, requires the participation of all the joints of theshoulder girdle. ➢ Acromioclavicular joint This joint has the particularity of being able to perform sliding movements of very lowamplitude, but in all planes of space. These movements allow the scapula to rotate and rockaround this point. The opening movement of the scapula relative to the clavicle is limited bythe conoid ligament, closing by the trapezoid ligament.