Shoulder instability exists on a continuum, and on the extreme end is complete dislocation, or when the ball of the joint becomes so loose it actually comes out of the socket. It’s also possible to partially dislocate your shoulder, called subluxation, which occurs when the shoulder almost slips completely out of the socket, but then pops back in. With subluxation, people often notice that their shoulder feels loose and slips in certain positions—often when their arm is raised over their head. Both subluxation and dislocation can also result from trauma, such as a fall or blow that occurs with enough force to overpower the strength of the muscles and ligaments of the shoulder.
If your shoulder dislocates, it’s important to seek medical help: As tempting as it may be to let someone place the bone back in the socket (once a dislocation is “reduced,” the severe pain stops almost immediately), an X-ray to rule out a fracture is a must. “Even if you know what you’re doing, you can sever a nerve with a piece of sharp bone,” says Dr. Stark.
Your doctor will return the ball of the joint to the socket, then control the residual pain and swelling with rest, NSAIDs, and possibly cortisone injections. You may also have your shoulder immobilized in a sling for a few weeks. Physical therapy is also usually required to regain full use of your arm. In some cases, surgery to tighten loose ligaments is necessary.