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The glenohumeral, or shoulder, joint is a synovial joint that attaches the upper limb to the axial skeleton. It is a ball-and-socket joint, formed between the glenoid fossa of scapula (gleno-) and the head of humerus (-humeral).
Acting in conjunction with the pectoral girdle, the shoulder joint allows for a wide range of motion at the upper limb; flexion, extension, abduction, adduction, external/lateral rotation, internal/medial rotation and circumduction. In fact, it is the most mobile joint of the human body. This shoulder function comes at the cost of stability however, as the bony surfaces offer little support. Instead the surrounding shoulder muscles and ligamentous structures offer the joint security; the capsule, ligaments and tendons of the rotator cuff muscles. Because of this mobility-stability compromise, the shoulder joint is one of the most frequently injured joints of the body.
| Type | Synovial ball and socket joint; multiaxial |
| Articular surfaces | Glenoid fossa of scapula, head of humerus; glenoid labrum |
| Ligaments | Superior glenohumeral, middle glenohumeral, inferior glenohumeral, coracohumeral, transverse humeral |
| Innervation | Subscapular nerve (joint); suprascapular nerve, axillary nerve, lateral pectoral nerve (joint capsule) |
| Blood supply | Anterior and posterior circumflex humeral, circumflex scapular and suprascapular arteries |
| Movements | Flexion, extension, abduction, adduction, external/lateral rotation, internal/medial rotation and circumduction |
| Rotator cuff muscles | Supraspinatus, infraspinatus, teres minor, subscapularis Mnemonic: Rotator cuff SITS on the shoulder |
This article will discuss the anatomy and function of the glenohumeral joint.
The glenohumeral joint is the articulation between the spherical head of the humerus and the concave glenoid fossa of the scapula. Being a synovial joint, both articular surfaces are covered with hyaline cartilage.
The glenoid fossa is a shallow pear-shaped pit on the superolateral angle of scapula. The concavity of the fossa is less acute than the convexity of the humeral head, meaning that the articular surfaces are not fully congruent. Congruency is increased somewhat by the presence of a glenoid labrum, a fibrocartilaginous ring that attaches to the margins of the fossa. The labrum acts to deepen the glenoid fossa slightly, it is triangular in shape and thicker anteriorly than inferiorly. The surface of the humeral head is three to four times larger than the surface of glenoid fossa, meaning that only a third of the humeral head is ever in contact with the fossa and labrum.
This incongruent bony anatomy allows for the wide range of movement available at the shoulder joint but is also the reason for the lack of joint stability. Instead, joint security is provided entirely by the soft tissue structures; the fibrous capsule, ligaments, shoulder muscles and their tendons.
The shoulder joint is encircled by a loose fibrous capsule. It extends from the scapula to the humerus, enclosing the joint on all sides. The internal surface of the capsule is lined by a synovial membrane.
On the humerus, the capsule attaches to its anatomical neck. Extending only at its medial margin, where the fibers protrude by around 1 cm. On the scapula, the capsule has two lines of attachments. The first is on its anterior and inferior sides where the capsule inserts into the scapular neck, posterior to the glenoid labrum. The second is on its superior and posterior aspects, where the capsular fibers blend directly with the glenoid labrum. Here the capsule arches over the supraglenoid tubercle and it’s long head of biceps brachii muscle attachment, thus making these intra-articular structures.
The capsule remains lax to allow for mobility of the upper limb. It relies on ligaments and muscle tendons to provide reinforcement. The anterior capsule is thickened by the three glenohumeral ligaments while the tendons of the rotator cuff muscles spread over the capsule blending with its external surface. These tendons form a continuous covering called the rotator capsule. It is comprised of the supraspinatus superiorly, infraspinatus and teres minor posteriorly, subscapularis anteriorly and the long head of triceps brachii inferiorly.
Two weak spots exist in this reinforced capsule. The first is the rotator interval, an area of unreinforced capsule that exists between the subscapularis and supraspinatus tendons. The second is the inferior capsular aspect, this is the point where the capsule is the weakest. The loose inferior capsule forms a fold when the arm is in the anatomical position. It becomes stretched, and least supported, when the arm is abducted.
The capsule has two openings;
Synovial fluid filled bursae assist with the joint’s mobility. The subdeltoid-subacromial (SASD) bursa is located between the joint capsule and the deltoid muscle or acromion, respectively. Similarly the subcoracoid bursae are found between the capsule and the coracoid process of the scapula. The subscapular bursa sits between the capsule and the subscapularis tendon, while the coracobrachial bursa is located between the subscapularis and coracobrachialis muscles. These bursae allow the structures of the shoulder joint to slide easily over one another.
Jump straight into the anatomy of the glenohumeral joint with this integrated quiz:
Explore our video tutorials, quizzes, articles and atlas images of glenohumeral joint for a full understanding of its anatomy.
Several ligaments limit the movement of the GH joint and resist humeral dislocation. These are the coracohumeral, glenohumeral and transverse humeral ligaments. Glenohumeral and transverse humeral are capsular ligaments while coracohumeral is an accessory ligament.
The transverse humeral ligament extends horizontally between the tubercles of the humerus. It covers the intertubercular sulcus and the long head tendon of the biceps brachii muscle, preventing displacement of the tendon from the sulcus. The coracohumeral ligament extends between the coracoid process of the scapula to the tubercles of the humerus and the intervening transverse humeral ligament, supporting the joint from its superior side. It acts to limit inferior translation and excessive external rotation of the humerus.
