Rotator Cuff of the Shoulder Joint
Definition
The rotator cuff (musculotendinous cuff) is a fibrous sheath formed by the blended tendons of four muscles that surround and reinforce the capsule of the shoulder joint. The tendons become flattened as they cross the joint and fuse with the capsule before reaching their insertions.
Mnemonic: SITS
- Supraspinatus
- Infraspinatus
- Teres minor
- Subscapularis
Muscles of the Rotator Cuff
| Muscle | Origin | Insertion | Nerve | Action |
|---|---|---|---|---|
| Supraspinatus | Medial 2/3 of supraspinous fossa | Upper facet, greater tubercle | Suprascapular (C5, C6) | Abduction (0–90°); stabilises head of humerus |
| Infraspinatus | Medial 2/3 of infraspinous fossa | Middle facet, greater tubercle | Suprascapular (C5, C6) | Lateral rotation |
| Teres minor | Upper 2/3, dorsal surface of lateral border of scapula | Lowest facet, greater tubercle | Axillary (C5, C6) | Lateral rotation |
| Subscapularis | Medial 2/3 of subscapular fossa (multipennate) | Lesser tubercle | Upper and lower subscapular (C5, C6) | Medial rotation and adduction |
Reinforcement of the Capsule
- Anteriorly: Subscapularis tendon
- Superiorly: Supraspinatus tendon
- Posteriorly: Infraspinatus and teres minor tendons
- Inferiorly: No cuff reinforcement — weakest point; site of common dislocation
Function
- Stabilises the head of humerus in the glenoid cavity during arm movements
- Compresses the humeral head against the glenoid (concavity-compression mechanism)
- Controls rotation of the humerus
- Together with the deltoid, forms a “force couple” for true abduction in the plane of the scapula
Clinical Significance
- Rotator cuff tear: Most commonly involves the supraspinatus tendon — the most vulnerable due to its passage under the coracoacromial arch
- Degeneration of the supraspinatus tendon may lead to calcification and spontaneous rupture
- Rotator cuff disorders are the most common cause of shoulder pain; typically occur in males after 50 years or with repetitive overhead activity (throwing, swimming, weight lifting)
- Tear leads to inability to initiate or sustain abduction