The shoulder is the most flexible joint in the body. Because it is able to move in so many directions, it can lead to an increased tendency for instability of the joint. This happens when the head of the upper arm bone is forced out of the shoulder socket.
Once the shoulder has dislocated once, it is vulnerable to repeated dislocations due to injury to the soft tissue and bony supports of the shoulder. When these dislocations are repeated it is called chronic shoulder instability.
The shoulder is made up of three bones: the upper arm bone (humerus), the shoulder blade (scapula) and the collarbone (clavicle). The shoulder is a ball-and-socket joint, which means the ball of the upper arm fits into a shallow socket in your shoulder blade.
The ball stays in the shoulder socket with the help of static restraints (labrum and ligaments) and dynamic restraints (the rotator cuff and scapular muscles). The rotator cuff is made up of four muscles that come together as tendons to form a covering around the head of the humerus. The rotator cuff attaches the humerus to the shoulder blade and helps to lift and rotate your arm.
The glenoid is the socket that the humerus fits in. This socket is surrounded by a fibrocartilaginous structure called the labrum that helps the head of the upper arm fit into the shoulder socket. Where the head of the humerus fits into the scapula is called the glenohumeral joint.
Shoulder dislocations can be partial, with the ball of the upper arm only partially coming out of the socket, referred to as a subluxation. However, a complete dislocation means the ball entirely leaves the socket.
Repeated dislocations cause the ligaments, tendons and muscles around the shoulder to become loose or torn. Chronic shoulder instability is the failure of these tissues to keep the arm centered in the shoulder socket.
What causes shoulder instability?
- Shoulder dislocation due to a severe injury or trauma. This is the most common cause of recurrent instability of the shoulder joint.
- Repetitive overhead strain on the shoulder joint from sports such as swimming, tennis or volleyball can also result in feelings of instability though the injury to the soft tissues is different then what is seen in athletes who have acute shoulder dislocations. This is often seen in people who also have hypermobile joints.
- A patient may have naturally loose ligaments throughout the body which results in a hypermobile joint (sometimes referred to as being double jointed) which can result in multidirectional instability.
What are the symptoms of shoulder instability?
- Shoulder pain
- Repeated shoulder dislocations
- Feeling of the shoulder “giving out”
- Feeling of the shoulder being loose or slipping in and out
How is shoulder instability diagnosed?
To determine whether you have instability in your shoulder, your physician will ask you for a complete medical history, have you describe your symptoms and conduct a physical examination.An X-ray or MRI may be necessary to confirm the diagnosis.
How is shoulder instability treated?
Initial treatment is nonsurgical and includes:
- Rest or change in activity
- Strengthening exercises and physical therapy
- Non-steroidal anti-inflammatory medicine such as ibuprofen
Surgery may be necessary if your pain causes disability and is not relieved with nonsurgical methods. Surgery helps to repair the ligaments so they are able to hold the shoulder joint in place.
Surgery options include:
- Minimally invasive arthroscopy: A physician will use tiny incisions, a camera and instruments to repair the soft tissues in the shoulder. This is often referred to as a labral repair or Bankart repair
- Open surgery: A physician will make a larger incision over the shoulder to repair the damaged tissues
After surgery patients are placed in a sling to limit their shoulder from moving. Physical therapy will be necessary to strengthen the shoulder joint and get range of motion back. The dynamic stabilizers are very important and strengthening is focused on the rotator cuff and scapular stabilizers to help with stability. Return to contact and overhead athletics is typically six to eight months after surgery.
Learn more about shoulder treatment at OrthoIndy.
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