Shoulder Impingement

Shoulder impingement is one of the most common causes of shoulder pain.  Rotator cuff is the four muscles (the supraspinatus, infraspinatus, subscapularis, and teres minor) that cover the ball of the shoulder joint (humeral head).  The muscles work to lift and rotate the shoulder.  As the arm is lifted above the shoulder, the underside of the acromion and coraco-acromial ligament (parts of the shoulder blade) rubs, or impinges on, the surface of the rotator cuff tendon.  The pain can be due to inflammation of the subacromial bursa (bursitis) or the cuff tendon itself (tendonitis).   With the progress of the problem, partial thickness tear to full thickness tear of rotator cuff tendon can occur.


  • Pain at rest or with movement
  • Deep discomfort in the upper arm
  • Pain with lifting, reaching and placing the arm behind the back
  • Overhead athletes may have pain when throwing or serving
  • Discomfort at night, especially if one rolls onto the sore shoulder
  • Weakness and reduced motion as it progresses

Risk Factors

Middle aged people who do repetitive lifting or overhead activities such as construction or painting are susceptible.  Young overhead athletes, such as swimmers, tennis players and basket players, are at high risk.  The pain can start spontaneously without any obvious cause.


Diagnosis begins with a medical history and precise examination by the doctor.  X-ray may show a small bone spur on the front edge of the acromion.  MRI examination can show inflammation of the bursa and the rotator cuff tendon.  Sometimes, partial tear of the tendon is seen.


Treatment consists of controlling the pain in order to allow rehabilitation of the rotator cuff muscles. The initial treatment involves oral non-steroidal anti-inflammatory medication and avoiding overhead activities.  Stretching exercises to improve the range of motion in a stiff shoulder will also help.  Injection of local anaesthetic and steroid into the subacromial bursa (there is a tiny risk of infection and allergic reaction), usually provides good pain control to allow rehabilitation.  Repeated injection is not recommended.  Rehabilitation should be supervised by a physiotherapist, as the technique is subtle.

If non-surgical treatment fails in relieving the pain, operative treatment is indicated. The operation consists of arthroscopic surgery (key holes surgery) of subacromial decompression (front edge of the acromion is removed) to give more space for the rotator cuff, removal of inflamed bursal tissue, and rotator cuff tendon debridement.

Post-operative rehabilitation

The arm is placed in a sling for a short period of time after the surgery.  The sling can be removed if comfort allows to initiate exercise and use of arm.  The rehabilitation includes exercise to regain range of motion and strength of the shoulder.  It usually takes two to three months to achieve full recovery.

Potential complication

Arthroscopic subacromial decompression involves a very small risk of wound infection and nerve injury.  Stiffness can be an issue if there is no supervised rehabilitation.  Some residual pain may be present but pain relief is usually good.

Written by Dr. Benjamin Chow