Question

1. List as many features as you can that facilitate the mobility of the glenohumeral joint. Think about the shape of the capsule, shape of the joint surfaces, ligaments, structures around the joint, accessory joints, and bones that contribute to full range of movement around the shoulder. Consider how these affect the mobility of the shoulder joint and shoulder complex, and how they may be a tradeoff for loss of stability.

Factors increasing mobility of the joint:

- Bones:

- Capsule:

- Synovial membrane & bursae:

- Muscles:

- Accessory joints:

- Scapulo-humoral rhythm:

Factors maintaining stability of the joint:

- Labrum:

- Rotator cuff:

- Ligaments:

- Tendons:

When you talk about each factor, please focus on its role in either mobility and stability. For example, you don't have to describe the attachment of the capsule and the ligaments, but what is specific in the capsule to increase mobility, and how each ligament supports and stabilizes the joint. Another example about the rotator cuff muscles, you don't have to describe each muscle in detail, but how they are the most important factor in maintaining the stability of the joint.

Answer 1

14. The shoulder joint or glenohumeral joint is a Synovial Joint of ball and socket variety. The mobility and stability of this joint are due to:

Bones like scapula which bears glenoid cavity on lateral border that is directed towards laterally and slightly upwards in order to form a ball and socket Variety of joint the head of humerus which is directed medially upwards and backwards forms one third of the sphere much larger than glenoid cavity. This type of arrangement permits greater mobility.

Capsule of shoulder joint attaches to margin of glenoid cavity of scapula and the Anatomical neck of humerus which is 2 cm down on medial side. Capsular ligament is very loose and permits free movements.

Capsule is lined by Synovial membrane which extends to form a tubular sheet for tendon of long head of biceps brachii. Bursae related to the joint or subacromial barsa, subscapularis barsa and intraspinatous bursa communicates with joint cavity and permit smooth motion.

Muscles related to shoulder joint that brought about the various movements of the joint are: clavicular head of pectoralis major, anterior fibres of deltoid causes flexion and posterior fibres of deltoid, latissimus dorsi causes extension. Pectoralis major, latissimus dorsi, biceps brachii short head, triceps brachii long head causes adduction and supraspinatus sergatus anterior, prapezius cause abduction, pectoralis major, deltoid (anterior fibres), latissimus dorsi, teres major cause medial rotation. Deltoid (posterior fibres), Infraspinatus, Teres major cause lateral rotation. Thus, these muscles are responsible for a wide range of movements of shoulder joint causing it, freely mobile.

Acromioaclavicular joint is formed by acromion of scapula and clavicle which helping or associated with movements of shoulder joint. Other joints include sternoclavicular and scapulothoracic joints.

Overhead movements of flexion and abduction of shoulder are brought about by smooth and co-ordinate motion of all joints of shoulder Complex mentioned about. Only glenohumeral joint motion cannot bring about 180 degree e off moment that takes place in overhead shoulder movement. Scapula contributes by rotating upwardly by 50 to 60 degrees. Glenohumeral joint contributes a total of 170 to 180 degrees of overhead movements. This makes overall ratio of 2° motion of shoulder to 1° motion scapulothoracic motion and it's called scapulohumeral rhythm.

Glenoid labrum is a fibrocartilaginous Rim which cover the margins of glenoid cavity and increases the depth of glenoid fossa for providing more stability.

Rotater cuff / musculotendinous cuff is a fibrous sheet formed by 4 flattened tendons of subscapularis, supraspinatus, infraspinatus, teres minor which blend with capsule of shoulder joint and strengthen it.

Coracohumeral ligament give the strength to capsule by connecting root of coracoid process to the neck of humerus. Transverse humeral ligament bridges upper part of bicipital groove of humerus providing way for passage of tendon of long head of biceps brachii.