Shoulder instability describes a range of conditions affecting the shoulder. Instability means that the shoulder joint is too loose and is able to slide around too much in the socket. In some cases the shoulder actually slips out of the socket and becomes dislocated. In a normal shoulder the ball portion of the joint moves approximately one inch forward or backward within the socket. Instability results when movement is too great and becomes painful.
Shoulder instability often follows an injury that causes the shoulder to dislocate. This initial injury is usually fairly significant. It is important that the shoulder be reduced, or put back in the socket. Sometimes individuals can achieve this on their own; however, often physician assistance is required in the Emergency Department. Two injuries occur with a dislocation that often leads to recurrent dislocations. (1) The labrum is often torn away from the bone. (2) The ligaments in the capsule are stretched (like a rubber band that has been overstretched- it becomes loose and floppy.) An unstable shoulder can result in repeated episodes of dislocation, even during normal activities.
In some cases, shoulder instability can happen without previous dislocation. People who do repeated shoulder motions may gradually stretch out the joint capsule. This is especially common in athletes such as baseball pitchers, swimmers and volleyball players. If the joint capsule gets stretched out and the shoulder muscles weaken the ball of the humerus begins to slip around too much within the shoulder. Eventually this can cause irritation and pain in the shoulder.
A genetic problem with connective tissues of the body can lead to ligaments that are too elastic. When ligaments stretch too easily, they may not be able to hold joints in place. All the joints in the body may be too loose. Some joints, such as the shoulder, may be easily dislocated. People with this type of condition are sometimes referred to as double jointed.
Signs & Symptoms
Chronic instability causes several symptoms. When the shoulder slips, but does not dislocate, or come completely out of the socket, it is called subluxation. The shoulder may actually feel loose. This commonly happens when the hand is raised above the head. Subluxation of the shoulder usually causes a quick feeling of pain, like something is slipping or pinching in the shoulder.
The shoulder may become so loose that it starts to dislocate frequently. This can be a real problem, especially if it can’t go back into the socket and must go to the emergency room for assistance to get the shoulder back into the joint. A shoulder dislocation is usually very painful and the shoulder may look abnormal in appearance. Any attempted movement results in extreme pain. A dislocated shoulder can also lead to damage of the nerves around the shoulder.
If the nerves have been stretched, a numb spot may develop on the outside of the arm, just below the top point of the shoulder. Several of the shoulder muscles may become slightly weak until the nerve recovers. The weakness is usually temporary.
Treatment of shoulder instability depends on several factors, and almost always begins with non-surgical options. If patients complain of a feeling that their shoulder is loose or about to dislocate, physiotherapy with specific strengthening exercises will often help maintain the shoulder in proper position. Shoulder strengthening is most likely to help those patients with multi-directional instability. It often takes several months of non-surgical treatment before an assessment to see if it is working. Other treatments include cortisone injections and anti- inflammatory medications.
If any of the above conservative treatment options fail, there are surgical options that can be considered depending on the cause of the instability.
- If the cause of the shoulder instability is a loose shoulder joint capsule, then a procedure to tighten the capsule of the shoulder may be considered.
- If the problem is due to a tearing of the ligaments around the shoulder, called the labrum, then a procedure called a Bankart repair can be performed to fix this ligament.
- The surgical operations that can be done in order to prevent shoulder dislocations are designed to repair and strengthen the ligaments that normally keep the shoulder in the joint.
After surgery, therapy progresses in stages. At first, the repair needs to be protected while the shoulder heals. To keep the arm from moving, a sling is most likely used and the arm cannot be used for the first 4 to 6 weeks. Full healing takes 12 to 16 weeks and occurs in 80-85% of patients who undergo surgery.