This tissue covers the shoulder joint and attaches the upper end of the humerus to the scapula. Your shoulder is also strengthened by strong tendons and muscles that keep the joint stable. Shoulder dislocation may be incomplete, it occurs when the head of the humerus moves only partially beyond the acetabulum. This is called a subluxation.
A complete dislocation means that the head of the humerus moves completely beyond the acetabulum. When the ligaments, tendons and muscles of the shoulder become too loose or torn, this leads to recurrent dislocations. Recurrent shoulder instability occurs when the shoulder is unable to hold the humerus in the center of the acetabulum.
Serious injury or trauma often causes primary dislocation of the joint. When the humeral head is dislocated, the acetabulum and ligaments in the front of the shoulder are often damaged. A ligament rupture at the front of the shoulder joint is called a bankart injury. Major primary dislocation can lead to recurrent dislocations, loss of function, or instability.
Repetitive strain on the joint
Some people with shoulder instability have never had a dislocation. Most of these patients have more loose ligaments in their shoulder joints. This excessive relaxation is sometimes their correct structure. Sometimes it is the result of repetitive movements with raised arms. Looser ligaments can make it difficult to maintain the stability of the joint. Repetitive or strenuous activities can be a big challenge for a weakened shoulder. This can result in a painful, unstable shoulder joint.
In a minority of patients, the shoulder joint may become unstable, even though there has been no injury or repetitive strain. In such cases, the arm may be loose or dislocated in different directions, which means that the head of the humerus can move forward, backward and downward from the acetabulum. This condition is known as multidirectional instability. These patients have naturally loose joints throughout their body and may have so-called hypermobility syndrome.
Common symptoms of recurrent dislocations include:
- Pain from shoulder injury.
- Repetitive dislocations of the shoulder joint.
- Repetitive instances of loss of ability to move.
- Persistent feeling of your arm becoming loose, ‘popping and hopping’ into a joint, or your arm ‘dangle loose’.
Physical examination and medical history. After discussing your symptoms and medical history, your doctor will examine your shoulder. Special examinations will help the doctor assess any instability in your shoulder joint. The doctor can also check that all ligaments are loose. For example, your doctor may ask you to try to touch the inside of your forearm with your thumb.