Shoulder Impingement

What is Impingement Syndrome?

Impingement Syndrome, which is sometimes called Swimmer’s shoulder or Thrower’s Shoulder, is caused by the tendons of the rotator cuff (supraspinatus, infraspinatus, teres minor and subscapularis muscles) becoming irritated and inflamed as they pass through a narrow bony space called the Subacromial Space – so called because it is under the arch of the acromion.

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.

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 acromiale), 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) stabilization 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.

Symptoms of impingement syndrome:

1. External impingement symptoms:

Primary
Pain at the front and/or side of the shoulder joint with overhead activity such as throwing, front crawl swimming.

Secondary
Pain at the front and/or side of the shoulder joint with overhead activity such as throwing, front crawl swimming.

2. Internal impingement symptoms:
Pain at the back and/or front of the shoulder when the arm is held out to the side (abducted) and turned outwards (external rotation)

Please see the Virtual Sports Injury Clinic for more information on how to treat Shoulder Impingement and other causes of shoulder pain.