The rotator cuff is made up of a group of muscles, ligaments and tendons that surround the shoulder joint, keeping the head of the upper arm bone firmly within the shallow socket of the shoulder. More specifically, the rotator cuff is a network of four muscles that come together as tendons to form a covering around the head of the humerus.
The four rotator cuff muscles include:
- Supraspinatus
- Infraspinatus
- Subscapularis
- Teres minor
Other muscles that help move and stabilize the shoulder include the deltoid, teres major, coracobrachialis, latissimus dorsi and pectoralis major.
The rotator cuff attaches the humerus to the shoulder blade and helps to lift and rotate the arm. There is a lubricating sac called a bursa between the rotator cuff and the bone on top of the shoulder (acromion). The bursa allows the rotator cuff tendons to glide freely when the arm is moved.
When one or more of the rotator cuff muscles/tendons is torn, the tendon no longer fully attaches to the head of the humerus. Most tears occur in the supraspinatus muscle and tendon, but other parts of the rotator cuff may also be involved. In many cases, torn tendons begin by fraying. As the damage progresses, the tendon can completely tear, sometimes with lifting a heavy object.
Damage to the rotator cuff tendons can occur because of acute injury, chronic overuse or gradual aging. This damage can cause significant pain and disability, with a reduced range of motion and use of the shoulder joint. When the rotator cuff tendons are injured or damaged, the bursa can also become inflamed and painful. A rotator cuff injury can cause a dull ache in the shoulder, which often worsens when the patient tries to sleep on the involved side.
Most tears occur in the supraspinatus muscle and tendon, but other parts of the rotator cuff may also be involved. In many cases, torn tendons begin by fraying. As the damage progresses, the tendon can completely tear, sometimes with lifting a heavy object.
There are two different types of tears:
- Partial tear. This type of tear damages the soft tissue, but does not completely sever it.
- Full-thickness tear. This type of tear is also called a complete tear. It splits the soft tissue into two pieces. In many cases, tendons tear off where they attach to the head of the humerus. With a full-thickness tear, there is basically a hole in the tendon.
Cause of rotator cuff tears
There are two main causes of rotator cuff tears: injury and degeneration.
- Acute tear – These types of rotator cuff tear can occur when a person falls down on the outstretched arm or lifts something too heavy with a jerking motion. Also, this type of tear can occur with other shoulder injuries, such as a broken collarbone or dislocated shoulder.
- Degenerative tear — Most tears are the result of a wearing down of the tendon that occurs slowly over time. This degeneration naturally occurs with aging. Rotator cuff tears are more common in the dominant arm. Several factors such as repetitive stress, lack of blood supply or bone spurs contribute to degenerative or chronic rotator cuff tears.
Symptoms of rotator cuff tears
Damage to the rotator cuff can vary from microscopic tears to large irreparable tears. Symptoms can include:
- Pain
- Weakness
- Restricted motion
- Catching
- Locking
- Feeling of instability
The symptoms are usually worse in certain positions, such as reaching backward to fasten a seat belt or pick up a briefcase out of the back seat. Symptoms can also be worse when the arm is elevated overhead, especially if there is weight on the arm, such as when picking up a stack of plates out of a cupboard. Overhead activities like pitching, throwing, playing tennis or playing racquet-ball commonly worsen symptoms.