The rotator cuff is a group of four muscles that hold your upper arm in place in your shoulder. It helps you make all the motions of your arm and shoulder.

The head of your upper arm bone, also called the humerus, fits into the socket of your shoulder blade, or scapula. When you extend your arm out away from your body, the rotator cuff muscles keep it from popping out of the socket, or glenoid.

Rotator cuff injuries are very common, especially in people over 40, athletes, and people whose work involves repeatedly lifting their arms overhead. Conservative treatments are usually successful.

Four muscles and their attached tendons make up the rotator cuff. Each of them aids in a specific motion of your shoulder. All together they help hold your upper arm in place in the shoulder socket.

All four muscles originate in your shoulder blade, but the other end of the muscle leads to different parts of your upper arm bone.

The acronym SITS can help you remember these four muscles:

  • Supraspinatus is responsible for movement away from the centerline of your body (abduction). The supraspinatus produces about the first 15 degrees of motion. After that, your deltoid and trapezius muscles take over.
  • Infraspinatus is the main muscle responsible for lateral rotation of your arm away from the centerline of your body. It’s a thick triangular muscle. It covers the back of your shoulder blade deep below the skin and close to the bone.
  • Teres minor is a small, narrow muscle on the back of your shoulder blade just below the infraspinatus. It also contributes to lateral (external) rotation of your arm.
  • Subscapularis is a large triangular-shaped muscle that lies below the other three. It’s the strongest, largest, and most used of the four rotator cuff muscles. It participates in most shoulder motions but is especially important for rotation of your arm toward the midline of your body (medial rotation). Unlike the other three muscles, the subscapularis attaches to the front, not the back, of your upper arm.

Each of these four muscles attaches to the upper part of your humerus at a different point. From top to bottom, their order is the same as the acronym:

  • Supraspinatus
  • Infraspinatus
  • Teres minor
  • Subscapularis

Many people who visit a doctor with shoulder pain have a problem with their rotator cuff.

A rotator cuff injury can happen suddenly, such as falling on your outstretched arm. Or it can develop slowly, resulting from repetitive motions or age-related degeneration.

Here are some of the types of rotator cuff injuries:

  • Tendinopathy. This is pain in and around the tendons. Tendinitis and tendinosis are variations. Rotator cuff tendinitis is considered the mildest form of rotator cuff injury. It can develop from:
    • age-related degeneration
    • overuse
    • repetitive motion
    • trauma
  • Impingement. This occurs when the top of the shoulder (the acromion) rubs against the tendon and the bursa and irritates the rotator cuff. Between 44 and 64 percent of all shoulder pain is thought to come from subacromial impingement syndrome (SAIS), which is the most common shoulder disorder.
  • Bursitis. The bursa around the rotator cuff can fill with fluid and swell.
  • Partial tears of the rotator cuff tendons. The tendon is damaged or frayed but isn’t torn away from the bone.
  • Full-thickness tears. The tendon is completely torn from the bone. Chronic degeneration is usually the reason.
  • Bone spurs. These can form when rotator cuff tendons rub on the shoulder bones. Bone spurs don’t always cause a rotator cuff injury.

Symptoms of rotator cuff injuries vary by individual. They may include:

  • pain in the shoulder area, usually described as a dull ache
  • difficulty in moving your arm in daily activities, like combing hair
  • weakness or stiffness in your shoulder muscles
  • pain that increases at night, making it difficult to sleep on the affected side
  • cracking or popping sounds when you move your arm

Some people with a rotator cuff injury may not feel any pain. The condition can be progressive, with degeneration occurring slowly. Only one-third of rotator cuff tears cause pain, according to a 2013 study.

Your treatment for a rotator cuff injury will depend on the type of damage. For most rotator cuff injuries, doctors prescribe conservative treatment.

Nonsurgical treatment

Conservative treatment includes:

  • rest
  • icing the area for 20 minutes at a time a few times a day
  • modifications of activities involving shoulder use
  • nonsteroidal anti-inflammatory drugs (NSAIDs) like ibuprofen, whether over-the-counter or prescription
  • exercises to stretch and strengthen the shoulder blade and other muscles
  • stretching while taking a hot shower
  • corticosteroid injections

Newer types of conservative treatment now under study include:

Research estimates that conservative treatment is effective in 73 to 80 percent of cases of full-thickness rotator cuff tears. Most people regain their range of motion and strength after 4 to 6 months.

Surgical treatment

If symptoms persist or worsen, your doctor may recommend surgery. Your doctor will also prescribe surgery for severe shoulder injuries.

Discuss with your doctor which type of surgery is best for your particular injury. Options include:

  • Open surgery. This is the most invasive. It may be needed for complex repairs.
  • Arthroscopic surgery. A miniature camera guides your surgeon to do the repair. This requires only small incisions. It’s the most common type of surgery.
  • Mini-open surgery. Your surgeon uses miniature instruments to do the repair. This requires only a small incision.

Recovery times from surgery vary depending on the type of surgery and extent of your injury. In some cases, healing can take up to 2 years, but most people are back to their normal activities and recover much sooner than that.

Most surgical repairs are successful. Talk with your doctor about ways to increase a good outcome. For example, if you smoke, this will involve quitting. People who smoke are more likely to have a poorer surgical outcome.

Physical therapy is important for rehabilitation after surgery, too.

If you have bothersome shoulder pain, it’s best to see your doctor for diagnosis and treatment. Treating rotator cuff injuries early can save you from increasing pain and the inability to use your arm and shoulder in daily activities.

The ball-and-socket structure of your shoulder and arm is an intricate arrangement of muscles, tendons, and bone. Injuries to the rotator cuff are common, but treatment is often successful.