Rotator Cuff

Introduction

Introduction to the Rotator Cuff

The rotator cuff is a group of four muscles and their tendons that surround the glenohumeral joint, providing dynamic stability and enabling precise movements of the upper limb. Located in the scapular-deltoid region, these muscles originate from the scapula and insert on the humerus. They are: supraspinatus (superior), infraspinatus (posterior), teres minor (posterior/inferior), and subscapularis (anterior). The deltoid muscle overlies them superficially. The rotator cuff compresses the humeral head into the glenoid fossa, preventing superior translation during abduction and maintaining joint integrity.

Study

Individual Muscles: Origin, Insertion, Action & Innervation

1. Supraspinatus: Origin – supraspinous fossa of scapula; Insertion – superior facet of greater tubercle of humerus; Action – initiates abduction (0–15°), assists deltoid; Innervation – suprascapular nerve (C5-C6). 2. Infraspinatus: Origin – infraspinous fossa; Insertion – middle facet of greater tubercle; Action – lateral (external) rotation; Innervation – suprascapular nerve (C5-C6). 3. Teres Minor: Origin – lateral border of scapula (upper two-thirds); Insertion – inferior facet of greater tubercle; Action – lateral rotation, weak adduction; Innervation – axillary nerve (C5-C6). 4. Subscapularis: Origin – subscapular fossa (anterior scapula); Insertion – lesser tubercle of humerus; Action – medial (internal) rotation, adduction; Innervation – upper and lower subscapular nerves (C5-C6).

Functional Anatomy & Stabilization

The rotator cuff functions as a force couple: supraspinatus provides superior compression; infraspinatus and teres minor provide posterior and lateral rotational forces; subscapularis provides anterior and medial rotational forces. Together they center the humeral head in the glenoid during arm movement. The rotator interval (between supraspinatus and subscapularis) contains the long head of biceps tendon and superior glenohumeral ligament, critical for anterior stability.

Clinical Relevance

Rotator cuff tears are common, especially supraspinatus tendon (due to hypovascular 'critical zone'). Impingement syndrome occurs when tendons are compressed under the coracoacromial arch. Tests: empty can (supraspinatus), external rotation lag (infraspinatus/teres minor), lift-off/belly-press (subscapularis). MRI or ultrasound confirms tears. Treatment ranges from physiotherapy to arthroscopic repair.

Summary

Key Takeaways – Rotator Cuff

SITS: Supraspinatus (abduction initiation), Infraspinatus (external rotation), Teres minor (external rotation), Subscapularis (internal rotation). All originate on scapula, insert on humeral tubercles. Innervation: suprascapular (supraspinatus & infraspinatus), axillary (teres minor), subscapular nerves (subscapularis). Critical for dynamic glenohumeral stability. Most common tear: supraspinatus near its insertion.