This instructional presentation provides a detailed lateral anatomical perspective of the glenohumeral joint (shoulder), focusing on the soft tissue structures essential for stability and movement, given the joint's inherent bony instability. The tutorial reviews the articulating surfaces of the humerus and scapula, emphasizing the shallow glenoid cavity and the deepening role of the glenoid labrum. A comprehensive dissection of the stabilizing ligaments, including the Coracohumeral, the three Glenohumeral, and the Coracoacromial ligaments, is provided. The majority of the presentation analyzes the muscular contributions to joint integrity, particularly the four muscles of the rotator cuff (Supraspinatus, Infraspinatus, Teres Minor, Subscapularis), and auxiliary stabilizers (Teres Major, Long Heads of Biceps and Triceps). Finally, it details the major associated bursae—the Subacromial/Subdeltoid complex and the Subtendinous bursa of the Subscapularis—and concludes with the clinical manifestation of subacromial bursitis and associated painful arc syndrome.
Lateral View Analysis of the Glenohumeral Joint
0:40 Joint Definition and Kinematics: The shoulder joint, or glenohumeral joint, is a highly mobile, proximal ball and socket type synovial joint allowing flexion, extension, abduction, adduction, rotation (medial/lateral), and circumduction.
1:42 Bony Elements: Humerus: Key features include the Head of the Humerus (articular surface), the Lesser and Greater Tubercles, the Inter-tubercular Groove (sulcus), and the Anatomical Neck.
2:19 Bony Elements: Scapula: Relevant features include the Glenoid Cavity (articular surface), the Supraglenoid and Infraglenoid Tubercles (muscle attachment sites), the Acromion Process (superior/posterior projection forming the shoulder girdle articulation), and the Coracoid Process (anterior projection, crucial ligament attachment site).
5:16 Joint Cavity and Stability: The glenoid cavity is shallow, and the humeral head surface is approximately four times larger, resulting in low bony stability. Stability is primarily derived from surrounding soft tissues.
6:06 Glenoid Labrum: A fibrocartilaginous ring attached to the margin of the glenoid fossa that functions to deepen the joint socket.
6:23 Joint Capsule: Composed of an outer fibrous layer and an inner synovial membrane, it encapsulates the humeral head, extending to the anatomical neck, creating the osteofibrous acetabulum.
7:16 Primary Ligaments: Ligaments strengthen the joint capsule, particularly anteriorly and inferiorly.
7:23 Coracohumeral Ligament: Runs from the posterior aspect of the Coracoid Process to the Lesser and Greater Tubercles of the humerus; prevents inferior displacement.
8:19 Glenohumeral Ligaments (S, M, I): Three distinct ligaments (Superior, Middle, Inferior) spanning from the scapula (supraglenoid tubercle and glenoid margin) to the humerus (tubercles/neck), enhancing anterior stability. These ligaments blend with the joint capsule.
9:43 Coracoacromial Ligament: Runs from the Coracoid Process anteriorly to the Acromion Process posteriorly, forming a protective superior arch over the joint. This ligament is completely separate from the joint capsule.
10:17 Muscular Stabilization: Rotator Cuff: A group of four muscles providing a compressive force to center and stabilize the humeral head against the glenoid cavity.
10:50 Supraspinatus Tendon: Crosses the superior aspect, blending with the joint capsule; originates from the supraspinous fossa and inserts on the greater tubercle.
11:20 Infraspinatus Tendon: Strengthens the posterior capsule; originates from the infraspinous fossa and inserts on the greater tubercle.
11:41 Teres Minor Tendon: Strengthens the posterior capsule inferiorly; originates from the lateral border of the scapula and inserts on the greater tubercle.
12:05 Subscapularis Muscle: The only anterior rotator cuff muscle; originates from the subscapular fossa and inserts on the lesser tubercle.
12:31 Teres Major: Crosses the joint inferiorly, originating from the inferior angle of the scapula and inserting on the medial lip of the inter-tubercular groove; does not blend with the joint capsule.
13:06 Long Head of the Triceps Brachii: Originates from the Infraglenoid Tubercle, crossing the joint distally.
13:35 Long Head of the Biceps Brachii Tendon: Originates from the Supraglenoid Tubercle, traveling within the joint capsule over the humeral head and into the inter-tubercular groove.
14:12 Associated Bursae (Cushioning): Fluid-filled sacs that reduce pressure and friction.
14:26 Subacromial Bursa: Located deep to the coracoacromial ligament and acromion process, cushioning the supraspinatus tendon. It extends laterally as the Subdeltoid Bursa (15:05) and typically does not communicate with the joint capsule.
15:37 Subtendinous Bursa of the Subscapularis: Located deep to the subscapularis tendon on the anterior aspect. This bursa normally does have an opening connecting it to the glenohumeral joint.
16:19 Clinical Correlation:Subacromial Bursitis (16:30) is inflammation of the bursa, often resulting from overuse or trauma, characterized by aggravation during abduction. Patients frequently exhibit Painful Arc Syndrome (16:58), experiencing pain between 60° and 120° of abduction due to compression of the inflamed structures under the acromion.