Instability of the shoulder joint

Why is the shoulder joint so easy to dislocate? The shoulder joint looks like a golf ball and the golf peg. The ball of the shoulder (humeral head) is very big but the golf peg (glenoid) is rather small in relation to it. To increase the size of the peg we have a rubbery “cuff” around it. This is known as the labrum.

Despite the rubbery cuff (labrum) the peg (glenoid) is still relatively small in relation to the ball of the shoulder (humeral head). If the patient falls in the right way the shoulder can dislocate very easily.

Shoulder dislocations and young people: Between the ages of 15 – 35 yrs., the patient has a significant change to dislocate the shoulder again after the first incidence. The reason for this is that the rubbery cuff (labrum) often tears from the peg (glenoid). This “reduces the size of the peg” and because of this the ball of the shoulder can more easily slip off.

There is a high likelihood that a young person will require surgery to prevent repeated dislocations of the shoulder.

Shoulder dislocations in older patients: After the age of forty it is unlikely that a patient will dislocate the shoulder again. Older patients have a high risk of tearing the rotator cuff muscles of the shoulder, rather. These tears are sometimes accompanied by a fracture of a part of the ball of the shoulder (greater tuberosita of the proximal humerus).

There for a shoulder sonar must always be performed a few days afterwards to make sure the supraspinatus muscle did not tear. It may not always be seen directly after the injury but may take some time. Should the patient have continued pain sometime after the dislocation, always remember to have a sonar done?