Impingement

Anatomy

Shoulder Anatomy - front view
Shoulder Anatomy - front view
Shoulder muscles (rotator cuff)- side view
Shoulder muscles (rotator cuff)- side view
Subacromial bursa - side view
Subacromial bursa - side view

Shoulder impingement syndrome (Subacromial impingement, painful arc) is a condition in which the tissues in the subacromial space become inflamed causing pain.

It is often difficult to distinguish between bursitis, tendinitis and small rotator cuff tears in the initial stages however the treatment is the same.

The condition may be caused or made worse by the shape of the acromion. If it is "hooked" it may rub on the tendons increasing the inflammation.

The tissues involved can be:

The bursa (lubricating sac) can become inflamed causing bursitis: The causes include: throwing sports and overhead activities such as painting, hanging wallpaper or washing windows. The chance of developing the condition increases with age.

The rotator cuff tendons: Causing tendinitis: This may occur when an overly aggressive training program is started by someone whose muscles are poorly conditioned (the post-Wimbledon syndrome) In younger athletes, the causes of tendinitis are similar to those of bursitis.

Calcium can be deposited in the tendons causing pain, again the chance of this increases with age.

What are the signs and symptoms?

There is usually no single acute initial episode and, at first, only minor pain and a slight loss of strength may be noticed. Loss of range of motion, especially the ability to lift the arm overhead, is often ignored for several months.

The symptoms of both conditions include

  • Mild to severe pain
  • Limited movement.
  • Inability to hold the arm in certain positions indicates tendinitis is present.
  • Recurrent episodes of tendinitis may indicate a rotator cuff tear.

The pain often has two forms

A continuous dull ache, which is often worse at night, is usually located over the lateral aspect of the shoulder joint and may extend someway down the side of the arm even as far as the elbow. Often it does not appear to be coming from the joint at all.

Sharp pain on lifting the arm is felt just below the acromion (the bony prominence at the top of the shoulder). The pain usually starts when the arm reaches horizontal and eases off if the arm can be brought all the way to vertical. This is the so called "painful arc".

How is the diagnosis made?

The doctor will listen to the description of the symptoms and examine the shoulder. Xrays will be taken to examine the shape of the acromion and to help exclude other pathology within the shoulder.

What is the initial treatment?

It is often not possible to differentiate between bursitis and tendinitis however the treatment is the same.

  • Avoidance of the aggravating activities.
  • Anti-inflammatory drugs should be used and may be all that is required.
  • Local injection of local anaesthetic and steroid often settle the acute episode.
  • After the inflammation subsides, the patient should do shoulder strengthening exercises.

If initial treatment doesn't work, what's next?

If the symptoms persist despite conservative treatment the shoulder will be re-examined to exclude a rotator cuff tear. It may be necessary to perform an arthroscopic subacromial decompression (acromioplasty) in which the undersurface of the acromion is shaved to prevent it rubbing on the rotator cuff.

Acromioplasty