The shoulder has a very shallow ball and socket joint. Because the shoulder joint is shallow, a normal shoulder will have a lot of mobility (think of all the different ways one can move their arm), however, issues can occur when the shoulder has too much mobility. Shoulder instability occurs when the ball moves around too easily in the socket.
To get a better idea of the shoulder's structure, watch this video on the anatomy of the shoulder.
Shoulder instability may result from a variety of different things. It can often follow an injury that causes the shoulder to dislocate. When the shoulder dislocates, the head of the humerus (the “ball”) is forced out of the glenoid (the “socket”). Dislocation may lead to Frozen Shoulder.
This is a traumatic injury that typically results in immediate medical attention to have the shoulder reduced, or when the ball is manually put back into the socket by a physician.
While the shoulder then appears to be normal, it may, in fact, continue to be unstable due to possible damages to the ligaments that help to hold the ball into the socket. When the ligaments become stretched or even torn, they become too loose, causing the shoulder to become unstable.
Shoulder instability can also follow an injury to the shoulder that is less severe. When people do repetitive motions with the shoulder, the shoulder can become stretched out creating a “looseness” in the shoulder. If this occurs and the muscles that surround the shoulder become weak, the ball begins to move around too much in the socket causing irritation and pain. This is commonly seen in overhead athletes like baseball pitchers, volleyball players, and swimmers.
Some people are genetically “loose-jointed” and have ligaments that stretch too easily making it difficult for the ligaments to hold the shoulder joint in place. People with this type of shoulder instability might not have a problem with day to day activities but will begin to have difficulty with repetitive or overuse activities.
Most people with shoulder instability will describe a sensation of shifting in the shoulder joint. They might complain that the shoulder feels as if it comes partially in and out of place (also known as subluxation). Some people will complain of pain at rest or with certain activities and might start avoiding activities that cause pain.
An orthopedic physician can typically diagnose shoulder instability through a patient’s medical history and physical exam. Sometimes diagnostic imaging such as X-rays or MRIs are used to determine the severity of the shoulder instability.
Based on the findings, the physician will determine whether conservative or surgical management is best. Conservative treatment may include immobilization in a sling, medication or injection to reduce pain and physical therapy.
In some cases, surgery is required to repair the structures of the shoulder to make it more stable. Whether the physician treats shoulder instability conservatively or surgical, most patients are referred to physical therapy.
The physical therapist will initially work on reducing pain; they may use modalities such as ice and electrical stimulation to help accomplish this. Once the pain has decreased, the focus will be on strengthening the muscles that surround to shoulder that help to stabilize the ball in the socket.
By retraining these muscles of the shoulder, the shoulder will move more smoothly, be less painful and have improved stability and return to desired activities.
Be sure to visit more JOI articles for more information about other injuries.