Impingement syndrome (trapped shoulder tendon)

Impingement syndrome is pain and often weakness when you raise your arm, caused by a muscle tendon 'catching' in your shoulder.

It involves the rotator cuff tendon – a tough, rubbery cord that connects your shoulder blade to your arm bone (see diagram, left). This tendon runs through a narrow space between the top of your arm bone and the shoulder blade.

In impingement syndrome, the tendon becomes trapped in this space and is repeatedly scraped against the shoulder blade, causing pain which tends to be worse when you raise your arm over your head, and at night.

It can start suddenly after an injury, or (generally from middle age onwards) it can come on gradually without any obvious cause.

What is the cause?

The space through which the rotator cuff tendon passes is quite narrow to begin with, especially when the arm is raised. Any condition that further narrows this space can cause the tendon to become trapped.

The most common causes are:

osteophytes (bony growths) growing from the shoulder blade into the space
calcium deposits that build up within the rotator cuff tendon
poor shoulder blade posture and muscle control

How is it diagnosed?

Your GP should be able to diagnose impingement syndrome by listening to your symptoms and examining your shoulder.

You may be asked to raise your arm to the side, with your palm facing away from your body (thumb down). This is usually painful in impingement syndrome.

Your GP may want to rule out other possible causes of shoulder pain, if the diagnosis isn't clear. You may be referred for a specialist assessment from a shoulder surgeon, which often involves a scan of your shoulder.

How is it treated?

Caring for your shoulder at home

If impingement syndrome is only mild then rest, ice and painkillers may be all that's needed.

You can follow this advice:

Rest the tendon. Avoiding any overarm movements will help prevent any further inflammation (swelling) or damage. Your doctor or physiotherapist will tell you how long you should rest it for, and when you should start exercises (see below).
Ice packs. Holding an ice pack to the shoulder for 15-20 minutes several times a day can help ease the pain. Do not put ice directly on your skin – wrap it in a towel. If you do not have an ice pack, wrap ice cubes or a bag of frozen vegetables in a towel and use this.
Painkillers. Mild non-steroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen, are effective at providing short-term pain relief and are available as tablets or a gel that you apply to the shoulder. Other painkillers, such as paracetamol, will also help ease the pain. If your pain is more severe, a stronger painkiller such as codeine can be prescribed.

Physiotherapy

While it is important to rest the shoulder joint, you shouldn't stop movement altogether. Inactivity will cause the muscles to weaken, which will worsen the problem, and your shoulder will stiffen up. For this reason, a sling is not usually recommended.

Your GP may refer you to a physiotherapist, who will be able to recommend some arm exercises – especially those for the shoulder blade muscles, as these are important in treating this condition.

Corticosteroid injections

Corticosteroids are medicines containing steroids, a type of hormone, that can be used to reduce inflammation. If there is swelling and evidence of inflammation, corticosteroids can be injected into the affected area of the shoulder.

Possible side effects include thinning and lightening of the skin.

Although corticosteroid injections can relieve pain, without physiotherapy they do not have a long-term effect and it is common for the pain to return. You can sometimes have another injection, but you will need to wait at least six weeks.

Surgery

If calcium deposits have formed in the tendon in your shoulder, they may need to be removed using surgery. This can be done using a technique called arthroscopy, which is keyhole surgery used to look inside a joint and repair any damage that has occurred. The cuts in your skin required for this surgery are small – around 5mm.

Alternatively, you may need to have an operation to widen the space under the roof of your shoulder so the tendon is no longer rubbing against the bone. This is also done as a keyhole (arthroscopy) operation. Your shoulder surgeon will explain the procedure to you and address any concerns you may have.