We use our rotator cuffs all the time in Pilates, in each movement of our arm. Let's learn about the muscles that make it up and their function! Our rotator cuff is often spoken about as a singular piece, as in "a rotator cuff tear". Actually, the rotator cuff is made of four muscles and their tendons. Together they stabilize our glenohumeral joint, articulate the humerus and play a role in scapular movement. Individually they are called subscapularis, supraspinatis, infraspinatis and teres minor.
Let's start deep with the subscapularis. The subscapularis runs along the anterior border of the scapula (meaning the side of your scapula that sits on your rib cage) and attaches to the lesser tubercle of the humerus. The subscap medially rotates the upper arm. You might think of this as internal rotation of your upper arm, when your elbow fold looks in towards your center line.
Supraspinatus starts at the supraspinous fossa of the scapula and slides under the acromioclavicular joint, inserting on the highest part of the greater tubercle of the humerus. The supraspinatus has two main functions, to help hold and stabliize the humeral head in the socket or glenoid fossa and abduction of the humerus for the first 30 degrees. Above 30 degrees of abduction your deltoid takes over. Abduction in the joint occurs when you move your arm out to the side away from your body.
Infraspinatus originates from the infraspinous fossa on the scapula and inserts on the greater tubercle of the humerus. The insertion for the infraspinatus on the humerus is behind and below the supraspinatus. The infraspinatus laterally rotates your humerus and assists in abduction (described above). You might think of lateral rotation as external rotation or when you turn the fold of your elbow away, looking out from your center line.
The teres minor originates from the lateral border of the scapula and inserts on the head of the humerus just below the infraspinatus. Teres minor also laterally rotates your humerus.
When you take a moment to consider the direction and attachments of these four muscles you can easily understand their role in holding your humerus steady during many movements.