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Am Fam Physician. 1999;59(10):2787

See related article on shoulder instability.

What is shoulder instability?

“Shoulder instability” is what doctors say you have when your shoulder goes a little out of place or feels like it might. “Instability” means that the shoulder bones aren't stable—they aren't held together as tight as they should be.

Is shoulder instability the same as shoulder dislocation?

No. When your shoulder goes completely out of place, it's called “dislocation.” The shoulder ligaments are torn and can't keep the joint in place. The signs of dislocation and instability might seem the same to you—weakness and pain.

The shoulder becomes unstable if the ligaments and muscles around it become weak. When ligaments and muscles get stretched too much, they get weak. Your shoulder muscles and ligaments might get stretched too much if you often throw a ball, hit hard with your shoulder in a football game or serve a volleyball really hard.

What are the signs of shoulder instability?

The main sign is pain in your shoulder. The pain can start suddenly or slowly. It may hit you just as you throw a ball, for example. If the injury happens suddenly, you may also feel numb all the way down your arm.

If shoulder instability comes on slowly over time, you may only notice pain at certain times. Shoulder motions like throwing may hurt, but the pain isn't as bad as the pain of a sudden injury. Your shoulder might be sore when you move it. It might feel loose in its joint. Your arm might feel weak.

How does my doctor find out I have shoulder instability?

Your doctor looks at your shoulder, moving your arm around to find signs of instability. Your doctor may also take x-rays. The x-rays will show if your shoulder bones are in the right place. You might get a special “picture” called a magnetic resonance image (or MRI, for short). An MRI lets your doctor see the bones and other parts of your shoulder.

How is shoulder instability treated?

Some people have surgery. Some people have physical therapy. It depends on how bad your shoulder is and how important it is for you to have a strong shoulder.

What else can I do?

Some people stop playing sports and avoid things that might hurt their shoulder again. If you don't want to give up sports or other activities, you can try weight-lifting exercises to make your shoulder muscles stronger.

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