Shoulder Impingement Syndrome

Shoulder Impingement

Impingement syndrome is sometimes called swimmer’s shoulder or thrower’s shoulder, and is caused by the tendons of the rotator cuff becoming trapped as they pass through the shoulder joint. It may follow a partial tear of a rotator cuff tendon, or come on gradually through overuse. Resting the shoulder and treating it as soon as possible will help to prevent long term damage.

Symptoms

Symptoms include pain which comes on gradually over a period of time. There will be a pain at the front and side of the shoulder joint, especially during overhead movements such as in throwing, racket sports, and swimming.

There may be a pain in the shoulder when the arm is held out to the side turned outwards (abduction and external rotation). Another give away sign of impingement is a pain in an arc from about 70 degrees to 130 degrees when lifting the arm out sideways and up above the shoulder.

Read more on assessment and diagnosis.

Causes & anatomy

What is impingement syndrome? Impingement of the shoulder, which is sometimes called swimmer’s shoulder or thrower’s shoulder, is caused by the tendons of the rotator cuff muscles becoming trapped or impinged as they pass through a narrow bony channel called the subacromial space. The subacromial space is so called because it is under the arch of the acromion. With repetitive pinching, the tendons become irritated and inflamed.

This can lead to thickening of the tendon which may cause further problems because there is very little free space, so as the tendons become larger, they are impinged further by the structures of the shoulder joint and the muscles themselves.

There are at least nine different diagnoses which can cause impingement syndrome which includes bone spurs, rotator cuff injury, labral injury, shoulder instability, biceps tendinopathy and scapula dysfunction. If left untreated, shoulder impingement can develop into a rotator cuff tear. The supraspinatus muscle is probably the most commonly involved in impingement syndrome of the shoulder.

Impingement Syndrome in itself is not a diagnosis, it is a clinical sign. There are at least nine different diagnoses which can cause impingement syndrome which includes bone spurs, rotator cuff injury, labral injury, shoulder instability, biceps tendinopathy and scapula dysfunction. If left untreated, shoulder impingement can develop into a rotator cuff tear.

It is thought shoulder impingement begins as an overuse injury of the supraspinatus tendon which runs along the top of the shoulder blade. Pain then prevents the rotator cuff muscles from working properly which causes the upper arm bone to shift slightly. This may also result in inflammation of the bursa or small sack of fluid (subacromial bursitis).

Over time the pain causes more dysfunction and impingement in a vicious circle which may eventually lead to ossification or bony spurs growing and causing injury to the rotator cuff tendons and so on. So it is vitally important that impingement syndrome is rested and treated as soon as possible to avoid long-term damage.

Shoulder impingement is classified as internal or external depending on the causes:

External impingement

External shoulder impingement is classified as primary or secondary.

  • Primary external impingement is usually due to bony abnormalities in the shape of the acromial arch in the shoulder joint. It can sometimes be due to congenital abnormalities are known as os acromial, or due to degenerative changes, where small spurs of bone grow out from the arch with age, and impinge on the tendons.
  • Secondary external impingement is usually due to poor scapular or shoulder blade stabilization which alters the physical position of the acromion, hence causing impingement on the tendons. Is often due to a weak serratus anterior muscle and a tight pectoralis minor muscles. Other causes can include weakening of the rotator cuff tendons due to overuse for example in throwing and swimming, or muscular imbalance with the deltoid muscle and rotator cuff muscles.

Internal impingement

This occurs predominantly in athletes where throwing is the main part of the sport, e.g. pitches in baseball or javelin throwers. The underside of the rotator cuff tendons impinges against the glenoid labrum. This tends to cause pain at the back of the shoulder joint as well as sometimes at the front.

Treatment

Treatment for shoulder impingement is based around reducing pain and inflammation, increasing mobility and strength whilst identifying and correcting the possible causes to ensure it does not recur.

Apply the PRICE principles of protection, rest, ice, compression, and elevation. Rest the shoulder from any painful activities or movements. Pain indicates increasing inflammation and delaying the healing process. Apply ice or a cold therapy and compression wrap to the painful area for 10-15 minutes per hour initially reducing to 3 or 4 times a day as symptoms reduce. Remember to use an ice bag or a towel wrapped around the ice to protect against ice burn.

A doctor may prescribe anti-inflammatory medication such as Ibuprofen to reduce pain and inflammation. A professional therapist may use electrotherapy such as ultrasound to help reduce pain and inflammation as well as advise on a suitable rehabilitation and exercise program.

Specific tests to confirm the diagnosis including X-Rays to what is causing the impingement. They may discuss the option of directly injected steroids into the subacromial space to reduce inflammation and reduce inflammation in the local area although this is not usually an early option. It is usually recommended after a period of at least 6-12 months.

Read more on treatment and rehabilitation.