Shoulder Impingement Syndrome

What is Impingement Syndrome?

Impingement Syndrome, which is sometimes called Swimmer’s shoulder or Thrower’s shoulder, is caused by the tendons of therotator cuff (supraspinatus, infraspinatus, teres minor andsubscapularis muscles) becoming ‘impinged’ as they pass through a narrow bony space called the Subacromial space – so called because it is under the arch of the acromion. With repetitive pinching, the tendon(s) 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.

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. These include:

• Bone spurs
• Rotator cuff disease/injury
• Labral injury
• Shoulder instability
• Biceps tendinopathy
• Scapula (shoulder blade) movement dysfunctions

If left untreated, shoulder impingements can result in a rotator cuff tear.

Impingement Syndrome can be classified as External or Internal:

1. External impingement, which can be either primary or secondary:

Primary

• Is usually due to bony abnormalities in the shape of the acromial arch.
• Can sometimes be due to congenital abnormalities (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

• Usually due to poor scapular (shoulder blade) stabilisation which alters the physical position of the acromion, hence causing impingement on the tendons.
• Is often due to weak serratus anterior and tight pectoralis minor muscles
• Other causes can include weakening of the rotator cuff tendons due to overuse (e.g. throwing and swimming) or muscular imbalance with the deltoid muscle and rotator cuff muscles.

2. Internal impingement

• Occurs predominantly in athletes where throwing is the main part of the sport (e.g. pitches in baseball)
• The under side of the rotator cuff tendons are impinged against the glenoid labrum – this tends to cause pain at the back of the shoulder joint as well as sometimes at the front.