What is a Rotator Cuff

Shoulder Joint Overview:

The Shoulder joint involves bones, muscles, tendons, ligaments and Synovial tissue. The shoulder joint is made up of three bones: the shoulder blade (Scapula), the collarbone (Clavicle) and the upper arm bone (Humerus). The shoulder is one of the most mobile joints in the body. It is a “ball and socket” joint, which holds the ball (the top, rounded part of the Humerus) in the socket (the shallow, depressed area called the Glenoid cavity, located on the outer edge of the Scapula)

What is the Rotator Cuff?

The Rotator Cuff muscles are connected individually to a group of flat tendons, which fuse together and surround the front, the back, and the top of the shoulder joint like a cuff on a shirt. The tendons attach the muscles to the bone and allow movement in the shoulder, as well as providing strength to hold the ball in its socket. They are involved in all shoulder motions: when the muscles contract, they pull on the rotator cuff tendon, causing the shoulder to rotate upward, inward, or outward, hence the name Rotator Cuff.

The Rotator Cuff ligaments attach bone to bone and provide stability to the shoulder joint bones.

Between the bones, muscle and other soft tissue there is the Bursa (a fluid filled sac) and Synovial fluid (lubricates your joint), which permit smooth gliding between the joint. They also protect the Rotator Cuff from the bony spurs or arches on the shoulder blade.

What muscles make up the Rotator Cuff?

The Rotator Cuff is made up of four small muscles situated close to the ball and socket joint of your shoulder (Glenohumeral joint). These muscles work as a unit, rather than individually. Often people injure one particular member of the Rotator Cuff (the most common diagnosis is Supraspinatus Tendinitis), however most injuries usually involve more than one muscle.

The Supraspinatus is the uppermost muscle of the Rotator Cuff which passes beneath the bone on the top of the shoulder (Acromion). This muscle permits lateral movement away from the midline of the body, so you can move your upper arm up the side and away (abduction). When your arm is raised in a forward position, this tendon and supporting bursa can be pinched (impingement), which causes them to become inflamed and swollen.

The Subscapularis is the Humeral head depressor and internal, medial rotator. This muscle allows you to move your upper arm inward and toward the centre of your body. It is located at the front of the shoulder.

The Infraspinatus is the external, lateral rotator which maintains dynamic joint stability. This muscle allows you to move your upper arm outward and away from the centre of your body (abduction). It is found at the back of the shoulder.

The Teres minor is the external, lateral rotator which maintains dynamic joint stability. This muscle allows you to move your upper arm outward and away from the centre of your body (abduction). It is located at the back of the shoulder.

What Causes a Rotator Cuff Injury?

Rotator Cuff injuries are very common, especially in people over 40 years of age. Most problems involve damage and irritation to the Rotator Cuff soft tissues (muscles, ligaments, tendons and bursa) rather than the bones, as they move frequently within a tight space. A Rotator Cuff injury usually begins as inflammation caused by some form of small but continuous source of irritation, such as repetitive overhead motions from sporting activities, work tasks or daily chores, which can lead to severe Tendonitis or Bursitis.

If you do not address the cause of the inflammation, a partial or complete tear can develop in your Rotator Cuff due to chronic wear and tear of the tendon. A tear may also result at any age from an acute or single traumatic event, such as a fall onto an outstretched arm.