Shoulder Impingement

Also known as

  • Impingement syndrome
  • Shoulder bursitis
  • Subacromial bursitis
  • Rotator cuff tendinitis

Shoulder impingement is a very common condition. It occurs when there is inflammation of the rotator cuff tendons and the bursa around them.

Your rotator cuff is a group of muscles around your shoulder joint. They are very important as these muscles play an essential role in moving your shoulder in all directions, especially when lifting your hand above your head and rotating your shoulder.

They also have the important function of keeping your shoulder joint in place. Without them, the ball of your shoulder joint would not sit or function properly in the socket of your shoulder joint.

A bursa is a fluid-filled sac that acts as a cushion between tendons, bones and skin. There are numerous bursae around the shoulder, but the most important one is called the ‘subacromial bursa’. It’s located above your shoulder joint and rotator cuff muscles, and protects them from rubbing on the bone above called the ‘acromion’.

Impingement syndrome is usually a combination of the tendons becoming inflamed (tendinitis) and the bursa becoming inflamed (bursitis).

shoulder impingement

Symptoms

The pain of shoulder impingement is felt over the outside and top of the shoulder. The signs and symptoms include:

  • Pain when lifting the arm out to the side, especially between shoulder height and overhead
  • Pain when reaching behind your back, doing up a bra or taking a wallet from a back pocket
  • Pain at night, particularly when lying on that side
  • A painful arc, where the shoulder hurts through part of the movement and eases again at the top
  • Weakness, often because movement hurts rather than because the muscle has failed

Night pain is often the symptom that leads people to seek help. The shoulder is not usually swollen, red or hot, and if it is, you should see your doctor.

Causes

There is a narrow space between the top of the arm bone and the bony roof above it, and the rotator cuff tendons and the bursa run through this space. When they are squeezed or rubbed, they swell and become sore. The swelling then makes the space tighter still, so the problem feeds itself.

Common triggers are repeated work or sport above the head, a sudden increase in activity, weakness of the muscles around the shoulder blade, and shoulder posture. The shape of the bony roof varies between people and plays a part, as does age, because tendons cope less well with load as we get older.

Risk Factors

Shoulder impingement is most common in people who work or play sport with the arm above the head. Factors that increase the risk include:

  • Jobs involving overhead reaching, such as painting, trades and shelf stacking
  • Overhead sports, including swimming, tennis, cricket, throwing sports and volleyball
  • A recent increase in training or overhead work
  • Age, most commonly from the forties onward
  • Weak muscles around the shoulder blade
  • A previous shoulder injury

Investigations

Your doctor can usually diagnose impingement by examining your shoulder, moving the arm in set ways to see which positions bring on the pain. Tests that may be used include:

  • Ultrasound, which shows the tendons and bursa well and can be done while the shoulder moves
  • X-ray, which does not show tendons but shows the shape of the bony roof and any arthritis
  • MRI, used when the picture is unclear or a rotator cuff tear is suspected

Complications

Most people recover, but where impingement is left untreated it can lead to:

  • Pain that carries on and disturbs sleep for months
  • A stiff shoulder, which develops if the arm is not used because it hurts
  • Wasting of the shoulder muscles
  • A rotator cuff tear, as long-standing irritation weakens the tendon

Treatment

Most people get better without an operation, although it takes time. Treatment includes:

  • Physiotherapy, which builds up the rotator cuff and the muscles around the shoulder blade
  • Cutting down overhead work for a period, rather than stopping using the arm
  • Simple pain relief and anti-inflammatory medication
  • A steroid injection into the space above the tendons, which can settle severe pain

Physiotherapy is the mainstay, and it should be given at least three months before it is judged to have failed. An injection works best where it is used to make the exercises possible, rather than on its own. Surgery is considered when pain has not improved after several months of proper physiotherapy, and involves making more room above the tendons. See subacromial decompression.

Prevention

The risk of shoulder impingement can be reduced by:

  • Keeping the rotator cuff and the muscles around the shoulder blade strong
  • Building up overhead work and overhead sport gradually
  • Taking breaks from long spells of reaching above your head
  • Warming up before overhead sport

If your shoulder starts to ache with a new activity, it is better to deal with it early than to push on.