Movements
The glenoid fossa is shallow and contains the glenoid labrum which deepens it and aids in stability. With 120 degrees of unassisted flexion, the glenohumeral joint is the most mobile joint in the body.
Scapulohumeral rhythm helps to achieve further range of movement. The Scapulohumeral rhythm is the movement of the scapula across the thoracic cage in relation to the humerus. This movement can be compromised by anything that changes the position of the scapula. This could be an imbalance in the muscles that hold the scapula in place which are the upper and lower trapezium. This imbalance could cause a forward head carriage which in turn can affect the range of movements of the shoulder.
The rotator cuff muscles of the shoulder produce a high tensile force, and help to pull the head of the humerus into the glenoid fossa.
| Movement | Muscles | Origin | Insertion |
|---|---|---|---|
| Flexion (150°–170°) |
Anterior fibers of deltoid | Clavicle | Middle of lateral surface of shaft of humerus |
| Clavicular part of pectoralis major | Clavicle | Lateral lip of bicipital groove of humerus | |
| Long head of biceps brachii | Supraglenoid tubercle of scapula | Tuberosity of radius, Deep fascia of forearm | |
| Short head of biceps brachii | Coracoid process of scapula | ||
| Coracobrachialis | Coracoid process | Medial aspect of shaft of humerus | |
| Extension (40°) |
Posterior fibers of deltoid | Spine of scapula | Middle of lateral surface of shaft of humerus |
| Latissimus dorsi | Iliac crest, lumbar fascia, spines of lower six thoracic vertebrae, lower 3–4 ribs, inferior angle of scapula | Floor of bicipital groove of humerus | |
| Teres major | Lateral border of scapula | Medial lip of bicipital groove of humerus | |
| Abduction (160°–180°) |
Middle fibers of deltoid | Acromion process of scapula | Middle of lateral surface of shaft of humerus |
| Supraspinatus | Supraspinous fossa of scapula | Greater tuberosity of humerus | |
| Adduction (30°–40°) |
Sternal part of pectoralis major | Sternum, upper six costal cartilages | Lateral lip of bicipital groove of humerus |
| Latissimus dorsi | Iliac crest, lumbar fascia, spines of lower six thoracic vertebrae, lower 3-4 ribs, inferior angle of scapula | Floor of bicipital groove of humerus | |
| Teres major | Lower third of lateral border of scapula | Medial lip of bicipital groove of humerus | |
| Teres minor | Upper two thirds of lateral border of scapula | Greater tuberosity of humerus | |
| Lateral rotation (in abduction: 95°; in adduction: 70°) |
Infraspinatus | Infraspinous fossa of scapula | Greater tuberosity of humerus |
| Teres minor | Upper two thirds of lateral border of scapula | Greater tuberosity of humerus | |
| Posterior fibers of deltoid | Spine of scapula | Middle of lateral surface of shaft of humerus | |
| Medial rotation (in abduction: 40°–50°; in adduction: 70°) |
Subscapularis | Subscapular fossa | Lesser tuberosity of humerus |
| Latissimus dorsi | Iliac crest, lumbar fascia, spines of lower 3-4 ribs, inferior angle of scapula | Floor of bicipital groove of humerus | |
| Teres major | Lower third of lateral border of scapula | Medial lip of bicipital groove of humerus | |
| Anterior fibers of deltoid | Clavicle | Middle of lateral surface of shaft of humerus |
Read more about this topic: Glenohumeral Joint
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