Origin: Most of the inner surface of the scapula, filling the subscapular fossa from vertebral to axillary border
Insertion: Lesser tubercle of the humerus and joint capsule .
Upper and lower subscapular nerve, arsing from the posterior cord of the brachial plexus via the ventral rami of nerve roots C5 and C6, and occasionally C7 .
Shoulder: The subscapularis internally rotates the shoulder and stabilizes the humeral head in the glenoid fossa.
The subscapularis is a deep muscle, lying on the anterior surface of the scapula in the subscapular fossa. However, the subscapularis occupies majority of the anterior face of the scapula, The upper and lower subscapular nerves, as well as the thoracodorsal nerve lies between the subscapularis and serratus anterior . On the lateral side Laterally the tendon of the subscapularis emerges behind the pectoralis minor. It continues under the proximal tendons of the biceps brachii and finally inserting into the fascial web of the anterior capsule, superior and middle glenohumeral ligaments, coracohumeral ligaments, the transverse humeral ligament and the periosteum of the lesser tubercle.
Stabilization: Stabilization of glenohumeral joint
Eccentrically : Shoulder external rotation
The supraspinatus works synergistically with the pectoalis major, latissimus dorsi and teres major to internally rotate the arm. The subscapularis, as part of the rotator cuff works synergistically with the infraspinatus, teres minor and supraspinatus to dynamically stabilize the glenohumeral joint.
Ideally internal rotation of the shoulder would be accompanied by posterior glide of the humeral head.
All muscles create not only osteokinematic motions, but may create force vectors that exaggerate the translation of the humeral head. For instance, the pectoralis major not only creates a force on the humerus that results in adduction and internal rotation, but the fiber direction also pulls anteriorly, contributing to anterior glide and roll of the humeral head.
The passive structures involved in providing an opposing translatory force include the joint capsule and ligaments, as well as, the tonicity of muscles not actively involved in the joint motion (for example the latissimus dorsi and teres major may assist in creating an inferior force, opposing the superior role noted during abduction due to their inherent tone and passive resistance to stretch) . The active resistance to translatory force is generally created by co-contraction of antagonists proximal to the joint itself. The rotator cuff may be viewed as tiny boosters attempting to maintain the humeral headTo Read More Register Now or Log in
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