Shoulder Instability

Published August 24, 2016 | By Adam Smith-Connor

Shoulder Instability

Hello << Test First Name >>The shoulder girdle is made up of 3 bones, the scapula (shoulder blade), the humerus (upper arm bone) and the clavicle (collar bone). The shoulder has the greatest range of motion of any joint in the body but this places it at the greatest risk of dislocations.

Shoulder instability is when the ball and socket joint is not controlled well. When the ball is sliding around it’s socket too much it can cause pain and in some cases come out of the socket and dislocate. Sometimes the ball does not completely dislocate and is only partially out and can feel locked. With a wiggle it often returns to its normal position. This is called subluxation.

To help improve the shoulder’s stability, the joint is supported by a thickened rim around the socket called a labrum, which deepens the shallow joint. The capsule around this joint is also reinforced by ligaments which become taught at the end range of all shoulder movements. When the ligaments become tight they also send important messages to the brain so that it can coordinate how the muscles around the shoulder move.

There are 4 very important muscles around the shoulder call the Rotator Cuff: supraspinatus, infaspinatus, teres minor and subscapularis. They are constantly adjusting to maintain the ball safely in the socket. They act a bit like dynamic ligaments throughout shoulders movement. They stabilise the joint during functional tasks of the arm, such as writing, driving and using the computer when the ligaments may not be tight.

There are 3 types of shoulder instability. The most common form of instability is caused by trauma, such as a fall. The large force causes structural damage to the ligaments and socket rim (labrum). This can lead to repetitive dislocations in some people. Shoulder rehabilitation may reduce the chances of this by training the rotator cuff to fully recover and compensate. In the younger population (below 28 years old) the chances of re-dislocation are much higher and they may require surgery.

The second type of instability is caused by excessive laxity of the shoulder ligaments and poor muscle control. This is not only of the rotator cuff, but also the muscles that control the scapula on the rib cage and to the rest of the body. It is difficult to keep the ball in a socket that is not controlled. This instability is known as atraumatic instability. It requires very specialist rehabilitation to achieve the complex muscle control. In some rare cases surgery can aid the muscle retraining process by tightening up the capsule and ligaments.

The third type is very rare and called “abnormal muscle patterning”. This is when the big powerful muscles that attach around the shoulder, activate inappropriately and out of sequence. This causes very large forces that the rotator cuff simply cannot compete with. This type of instability requires very specialist physiotherapy. We aim to reteach these muscles to activate in a normal way and rewrite their programming. Occasionally, the first 2 types of shoulder instability may develop these characteristics and it is important that this is identified early and addressed.

Due to the complex nature and wide spectrum of symptoms of shoulder instability, shoulder surgeons and Physiotherapists work very closely together to manage this condition.

New Forest Physiotherapy Southampton
40 Kingfisher Way, Marchwood, Southampton SO40 4XS	Telephone: 023 8008 9120 \| Email: contact@newforestphysio.co.uk