What is the shoulder joint complex and what does it include?

The shoulder joint complex is a system of four articulations that work together to enable the upper limb's wide range of motion. It includes the glenohumeral joint (the true shoulder joint), the acromioclavicular joint, the sternoclavicular joint, and the scapulothoracic articulation (a functional joint). This arrangement allows for precise hand positioning and free movement.

What type of joint is the glenohumeral joint and what are its key structures?

The glenohumeral joint is a synovial ball-and-socket joint. It connects the rounded head of the humerus to the shallow glenoid cavity of the scapula, with the glenoid labrum deepening the cavity to improve stability.

What are the main ligaments of the shoulder joint and their functions?

Key ligaments include the capsular ligament, which encloses the joint; the glenohumeral ligaments (superior, middle, inferior), reinforcing the anterior capsule; the coracohumeral ligament, extending from the coracoid process to the greater tubercle; the transverse humeral ligament, forming a canal for the biceps tendon; and the coracoacromial ligament, which helps protect the joint superiorly.

What is the mechanism of abduction at the shoulder joint?

Abduction involves a coordinated sequence: up to 90° at the glenohumeral joint, 90°–120° requiring lateral rotation of the humerus, and 120°–180° involving scapular rotation. This follows the scapulohumeral rhythm with a 2:1 ratio of humeral to scapular movement.

What are some common clinical conditions affecting the shoulder joint?

Common conditions include subacromial bursitis, which can cause a painful arc syndrome; shoulder dislocation, often inferior and potentially damaging the axillary nerve; frozen shoulder (adhesive capsulitis), involving capsular shrinkage; and rotator cuff disorders, such as tendinitis or impingement.

What is the blood and nerve supply to the shoulder joint?

The joint receives blood from arteries like the anterior and posterior circumflex humeral, suprascapular, and subscapular arteries. Nerve supply includes the axillary, suprascapular, and musculocutaneous nerves.

Shoulder Joint Anatomy – Ligaments, Movements & Dislocation