Rotator Cuff Muscles – What They Are And How Do They Work

In our latest health and fitness blog, we look at rotator cuff muscles and examine their purpose and how they function.

Rotator cuff muscles are a group of four muscles that serve to stabilise the shoulder joint during movement and prevent dislocation. One is positioned at the top of the humeral head, one on the front of the humerus and two on the back of the humerus.

All the rotator cuff muscles originate from the scapula and insert into the upper humerus. The four muscles are:

• Supraspinatus
• Infraspinatus
• Teres minor
• Subscapularis

The supraspinatus is the most superior of the muscles and connects on to the top of the humeral head. It’s origin is the supraspinatus fossa of the scapula, which is a tunnel running from the medial side of the superior aspect of the scapula to the humeral head. Its action is to initiate the process of abduction at the shoulder joint, which the deltoid will then take over.

The infraspinatus is a slightly larger surface area muscle, which originates from the posterior aspect of the scapula and connects on to the posterior aspect of the head of the humerus. This rotator cuff muscle laterally rotates the humerus and helps prevent posterior dislocation of the shoulder joint.

The teres minor originates in the upper two-thirds of the lateral edge of the dorsal surface of the scapula and the insertion is on the back of the greater cubicle of the humerus. Working as a rotator cuff muscle, it rotates the humerus laterally and helps prevent upward dislocation of the shoulder joint.

The subscapularis is the only rotator cuff muscle positioned on the anterior surface of the scapula – all the others originate from the back. It comes on to the front of the humerus and aids the medial rotation of the shoulder joint. It originates in the suprascapular fossa and its insertion is the lesser tubercle out of the top of the humerus. As a rotator cuff it stabilises the shoulder joint and prevents the top of the humerus being pulled upwards by the deltoid biceps, dislocating the shoulder.