Shoulder Joint Ligaments

Diagrams

1. Glenohumeral Ligaments (GHLs)

A. Superior Glenohumeral Ligament (SGHL)

• Attachment: Anterosuperior glenoid rim (near apex of labrum, conjoined with long head of biceps) → intertubercular groove and lesser tubercle of humerus
• Function: Limits inferior translation and external rotation of the adducted shoulder. Together with the coracohumeral ligament, it forms the rotator interval
• Taut position: 0° abduction (arm at side)

B. Middle Glenohumeral Ligament (MGHL)

• Attachment: Upper margin of glenoid cavity → anatomic neck of humerus (passes almost at a right angle to the subscapularis tendon)
• Function: Secondary restraint to anterior translation; limits external rotation at ~45° abduction
• Clinical note: Highly variable in size - may be absent (e.g., Buford complex: cord-like MGHL + absent anterosuperior labrum, found in ~1.5-2% of individuals)

C. Inferior Glenohumeral Ligament (IGHL)

• The most important glenohumeral ligament
• Attachment: Inferior glenoid margin → distal lesser tuberosity / proximal humeral shaft
• Three components:
  • Anterior band (ABIGHL) - primary restraint to anterior dislocation; most important restraint in abduction + external rotation
  • Posterior band (PBIGHL) - resists posterior instability in flexion + internal rotation
  • Axillary pouch (recess) - lies between the two bands; forms a "hammock" during abduction
• Function: Primary restraint to anterior, posterior, and inferior glenohumeral translation. The major restraint to external rotation in neutral and abducted positions
• Taut position: Arm in abduction and external rotation

2. Coracohumeral Ligament (CHL)

• Attachment: Base of coracoid process → greater and lesser tubercles of humerus (two parts/bands)
• Function:
  • Limits inferior translation and external rotation of the adducted shoulder (in conjunction with SGHL)
  • Stabilizes the tendon of the long head of biceps brachii as it passes through the intertubercular groove
  • Forms the roof of the rotator interval (together with SGHL and part of the joint capsule)
• Clinical note: Contracture of the CHL is implicated in adhesive capsulitis (frozen shoulder)

3. Coracoacromial Ligament (CAL)

• Attachment: Undersurface of the medial acromion → superolateral border of coracoid process
• Function:
  • Forms the coracoacromial arch (with acromion and coracoid) - provides a roof over the humeral head, prevents superior dislocation
  • Acts as a tension band between acromion and coracoid, transmitting forces from surrounding muscles
  • The subacromial bursa lies between the CAL and the rotator cuff tendons
• Clinical note: The CAL limits upward movement of the humerus. Thickening or osteophytes under it cause subacromial impingement

4. Transverse Humeral Ligament

• Attachment: Greater tubercle → lesser tubercle of humerus
• Function: Bridges the intertubercular (bicipital) groove, holding the long head of the biceps tendon in place within the groove
• Clinical note: Disruption can allow the biceps tendon to sublux or dislocate out of the groove

5. Rotator Interval

• SGHL
• Coracohumeral ligament
• Part of the joint capsule

Positional Function Summary

Key Clinical Points

• The capsule is broad and thin posteriorly - not reinforced by ligaments, hence posterior dislocations can occur with fewer restraints
• The axillary recess (inferior capsular fold) provides reserve capacity for abduction; with prolonged disuse it can become atrophic - contributing to adhesive capsulitis
• The joint cavity communicates with the subtendinous bursa of subscapularis and the biceps tendon sheath within the intertubercular groove
• The IGHL anterior band is the single most important restraint to anterior dislocations

Shoulder Joint Ligaments - Simplified

The Main Ligaments

1. Glenohumeral Ligaments (3 bands on the front of the joint)

2. Coracohumeral Ligament

• Runs from the coracoid process → humerus
• Stops the arm from dropping downward when at rest
• Keeps the biceps tendon in its groove

3. Coracoacromial Ligament

• Runs from coracoid process → acromion
• Forms a roof over the shoulder (coracoacromial arch)
• Prevents the humeral head from popping upward
• When this arch is too tight → impingement syndrome

4. Transverse Humeral Ligament

• A small strap across the bicipital groove
• Holds the biceps tendon in place

Simple Memory Aid

"3 GH bands front, 1 roof above, 1 strap on top, 1 strap across the groove"