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St. Mary's Center for Orthopaedics

Shoulder Impingement Syndrome

What is Impingement Syndrome of the Shoulder?

Shoulder impingement syndrome is a painful condition in the shoulder.  It occurs when the tendons in the shoulder are irritated, inflamed or degenerated from repetitive overhead motions or structural abnormalities in the shoulder.  Impingement syndrome is a common shoulder condition seen in aging adults. This condition is closely related to shoulder bursitis and rotator cuff tendonitis. These conditions may occur alone or in combination.  Shoulder impingement syndrome is treated with activity modification, medication, and therapy.  When non-surgical options fail, surgical treatment may be used to relieve symptoms and restore function.

Shoulder Anatomy

In most parts of the body, bones are surrounded by the muscles. In the shoulder region, however, the muscle is surrounded by bone. This unique arrangement of muscle between bone leads to the condition of impingement syndrome (shoulder bursitis, rotator cuff tendonitis). The shoulder is composed of three bones.  The humerus is the upper arm bone.  The clavicle is the collarbone.  The scapula is the shoulder blade that moves on the back.  A prominent edge of the scapula, the acromion, forms the top of the shoulder.

The head of the humerus is round.  It rotates in a shallow basin on the scapula called the glenoid.  A group of ligaments, called the joint capsule, hold the head of the humerus in position.  Ligaments are strong tissues that connect bones and provide stability.  In other words, the joint capsule is responsible for holding the upper arm in place at the shoulder.

Four muscles at the shoulder form the rotator cuff of tendon that connects to the head of the humerus.  The muscles allow the arm to rotate and move upward to the front, back, and side.  A gliding membrane, the bursa, lubricates the rotator cuff tendons and reduces friction around them when they move.

The rotator cuff muscles are used whenever you perform overhead motions, such as lifting your arms up to put on a shirt or reaching for an item on a shelf.  These motions are used repeatedly during sports, such as serving in tennis, pitching in baseball, stroking in swimming, and passing in football.  Overhead motions may also be used for job duties, such as for construction.

When an injury to the rotator cuff muscle occurs, the muscle responds by swelling much the way an ankle does when it is sprained. However, because the rotator cuff muscle is surrounded by bone, its swelling causes a number of events to occur. The pressure within the muscle increases, resulting in compression and loss of blood flow in the small blood vessels called capillaries. When the blood flow is diminished, the muscle tissue begins to fray much like a rope. As the muscle tissue swells, it results in pain.  Pain is aggravated by actions such as reaching up behind the back and reaching up overhead. Night pain resulting from this shoulder condition may result in sleep interruption.

What Causes Impingement Syndrome of the Shoulder?

Shoulder impingement syndrome usually occurs as a result of muscle imbalance around the shoulder that place increase stress on the rotator cuff tendons.  Secondary impingement syndrome results from the rubbing or pinching of the tendons and bursa during repetitive overhead movements. Shoulder impingement syndrome occurs when the space beneath the acromion is too small for the rotator cuff tendons.  The space may be too narrow because of structural abnormalities in the shoulder bones, bone spurs, or thickened tissues.

As the tendons and bursa rub together during movement, it causes friction, pain, and limited motion.  Degenerated tendons can become painful.  Tendons may develop tendonitis, and the bursa may develop bursitis.  Both are painful conditions.  Continued inflammation can cause the rotator cuff tendons to tear or detach from the top of the humerus.

What are the Symptoms of Impingement Syndrome of the Shoulder?

Typical symptoms of shoulder impingement syndrome include:

  • Difficulty reaching up behind the back
  • Pain when the arms are extended above the head
  • Weakness of shoulder muscles

If shoulder muscles are injured for a long period of time, the muscles can actually tear in two. The resulting injury is called a rotator cuff tear. This causes very significant weakness and, on occasion, inability to elevate the arm against gravity. Some patients will have rupture of their biceps muscle as part of this continuing impingement process.

How is Impingement Syndrome of the Shoulder Diagnosed?

  • Diagnosis begins with a medical history and physical examination.
  • X-rays may be ordered to rule out arthritis and will show changes in the bone that reflect the injury of the muscle.
  • A magnetic resonance imaging (MRI) scan may be used to show more detailed pictures of your shoulder, particularly the rotator cuff, the muscles and joint capsule.  There may be bone spurs present or changes in the normal contour of the bone where the rotator cuff muscles normally attach.
  • An impingement test, which involves injecting a local anesthetic into the bursa, can help to confirm the diagnosis.

How is Impingement Syndrome of the Shoulder Treated?

The vast majority of patients who have impingement syndrome are successfully treated with the following:

  • Rest from the irritating activity
  • Ice packs
  • Medication for pain and inflammation
  • Cortisone injections may be used
  • Physical therapy to regain motion and strengthen weakened muscles, thereby decreasing pain.

Treatment may take several weeks to months. Many patients experience a gradual improvement and return to function.

Surgery is recommended when non-operative treatments have provided minimal or no improvement of the symptoms.  The goal of surgery is to remove the impingement and create more space for the rotator cuff. This allows the humeral head to move freely in the subacromial space and to lift the arm without pain.

The most common surgical treatment is subacromial decompression or anterior acromioplasty. This may be performed by either arthroscopic or open techniques:

  • Arthroscopic technique: In an arthroscopic procedure, two or three small puncture wounds are made. The joint is examined through a fiberoptic scope connected to a television camera. Small instruments are used to remove bone and soft tissue.
  • Open technique: Open surgery requires placement of a small incision in the front of the shoulder. This allows for direct visualization of the acromion and rotator cuff.

In most cases, the front (anterior) edge of the acromion is removed along with some of the bursal tissue. The surgeon may also treat other conditions present in the shoulder at the time of impingement surgery. These can include:

  • Acromioclavicular arthritis
  • Biceps tendonitis
  • Partial rotator cuff tear

Recovery Following Impingement Syndrome Surgery

After surgery, the arm may be placed in a sling for a short period of time. This allows for early healing. As soon as comfort allows, the sling may be removed to begin exercise and use of the arm. The surgeon will provide a rehabilitation program based on the patient’s needs and the findings at surgery. This will include exercises to regain range of motion of the shoulder and strength of the arm. It typically takes two to four months to achieve complete relief of pain, and may take up to a year.