Shoulder impingement

What is shoulder impingement?

Shoulder impingement happens when a tendon (or the small fluid-filled cushion beside it, called a bursa) gets squeezed between the bones of your shoulder as you lift your arm, causing pain. Experts believe it's behind roughly half of all shoulder pain, making it one of the most common shoulder problems.

What are the symptoms of shoulder impingement?

Symptoms usually build up gradually over weeks or months, though they can occasionally start suddenly after an injury. Common signs include:

• pain at the top or front of your shoulder, sometimes spreading down the side of your arm
• pain that's worse when you raise your arm, particularly overhead, or reach behind your back
• aching at night, particularly when lying on the affected side, which can disturb your sleep
• weakness in your arm or shoulder, and general tenderness to the touch
• stiffness, or a cracking or popping feeling when you move your shoulder.

Some people also notice tingling that spreads down the arm. This can also be a sign of a trapped nerve in the neck, so it's worth seeking advice from your GP rather than assuming it's impingement.

What causes shoulder impingement, and who is at risk?

Above your shoulder joint sits an arch formed by a bone called the acromion. The space beneath it, where your rotator cuff tendons pass through, can become narrower than usual, so the tendon (or the bursa cushioning it) gets pinched every time you lift your arm. It isn't always clear whether the narrowing causes the tendon damage, or existing tendon damage causes the narrowing; in practice, it's often a bit of both.

Shoulder impingement is usually an overuse problem, developing gradually from repeated stress on the shoulder, though a fall or other injury can occasionally bring it on suddenly. Things that make it more likely include:

• repetitive overhead movement at work or in sport, such as swimming, tennis, volleyball or throwing sports
• manual jobs involving prolonged overhead arm positions, including construction, decorating, window cleaning or hairdressing
• getting older, since tendons naturally become more vulnerable with age; it's most commonly seen between 60 and 70
• poor posture, and an acromion bone that's naturally shaped with a curve or hook instead of being flat, which some people are simply born with
• bony growths that can develop on the acromion over the years
• conditions such as diabetes or rheumatoid arthritis.

Are there different types of shoulder impingement?

Doctors sometimes describe shoulder impingement by which structure is affected:

• rotator cuff tendinitis, where one of the rotator cuff tendons itself becomes swollen and irritated
• shoulder bursitis, where the small fluid-filled cushion (bursa) between the tendons and shoulder blade becomes inflamed
• impingement linked to the shape of your acromion, which may be naturally curved or hooked, or have developed bony growths over time.

It can also be classified by where in the shoulder the pinching happens. The most common form, subacromial impingement, affects the tendon (usually one called the supraspinatus) directly beneath the acromion.

Less commonly, subcoracoid impingement affects a different tendon nearer the armpit, and internal impingement, which is rare and mostly seen in throwing athletes such as baseball pitchers, affects a tendon at the back of the joint.

How is shoulder impingement diagnosed?

Your doctor or physiotherapist will ask about your symptoms, work, hobbies and any previous injuries, then examine your shoulder's range of movement and tenderness.

Two specific hands-on tests are commonly used: one involves lifting your arm forward while your shoulder blade is held steady, and the other involves gently rotating your arm inward while your elbow is bent against your body. Pain during either points towards impingement.

Imaging isn't always necessary for a working diagnosis, but an X-ray, ultrasound or MRI scan may be used to rule out other explanations, such as a rotator cuff tear, arthritis or a biceps tendon injury.

How is shoulder impingement treated?

Most people improve with non-surgical treatment: between around 70% and 90% recover well with physiotherapy alone.

Non-surgical treatment

• modifying activities that bring on the pain, particularly repeated overhead movements, while staying as active as you comfortably can
• a cold compress or bag of ice, wrapped so it isn't in direct contact with your skin, held on for 10 to 20 minutes at a time, a few times a day
• paracetamol, ibuprofen or an anti-inflammatory gel for pain relief, though anti-inflammatory tablets are generally best used short-term (some sources suggest no more than 7 to 14 days) unless your doctor advises otherwise
• physiotherapy, with exercises tailored to rebuild strength and movement in your shoulder
• a steroid injection, if rest, exercise and painkillers haven't been enough on their own.

It's best not to rest your shoulder completely, for example by keeping it in a sling. Gently continuing to move the joint, within your comfort, helps prevent it from becoming weak or stiff, and most people start feeling better within a few weeks to a few months, though full recovery can occasionally take up to a year.

Steroid injections can settle the pain completely, or in some cases only for a short period before wearing off, and can be repeated alongside continued exercise. Because they carry a small risk of tendon damage with repeated or long-term use, they're generally reserved as a later option once simpler measures haven't fully worked.

Surgical treatment

If symptoms don't settle with rest, exercise and injections, surgery may be considered. This usually involves a keyhole (arthroscopic) procedure called a subacromial decompression, where the surgeon removes a small amount of bone to create more room for the tendon so it no longer catches.

If a rotator cuff tear is found at the same time, this can sometimes be repaired during the same operation. Most people go home the same day or the day after.

When should I see a doctor?

See a GP or physiotherapist if:

• your shoulder pain hasn't improved after a few weeks
• the pain is stopping you doing your usual daily activities, work or sport
• you have ongoing weakness, stiffness or difficulty moving your shoulder comfortably.

It's worth getting checked sooner rather than later: shoulder impingement generally responds well to treatment, but left alone it can worsen and, over time, contribute to a rotator cuff tear.