What is shoulder impingement?

DEAR DOCTOR K:

I have pain in my shoulder when I raise my arm above my head. My doctor says it’s caused by “impingement.” What does that mean, and what can I do about it?

DEAR READER:

You know the wide variety of things your shoulder allows you to do — such as reach for a box of cereal, swing a golf club and wash your hair. Its wide range of motion makes all these things possible. However, the design of a joint that lets you do all of that also leaves the joint vulnerable to injury.

Joints are places where two or more bones meet. The shoulder joint is where three bones meet: the clavicle (collarbone), the scapula (shoulder blade) and the humerus (upper arm bone).

The shoulder is a highly mobile ball-and-socket joint. The top of the humerus is a ball of bone that sits in the bony socket formed by the clavicle and scapula. The ball-and-socket construction allows the arm to move freely. It moves when muscles, tendons and ligaments tug on the bone to move it. That group of muscles, tendons and ligaments is called the rotator cuff. (I’ve put an illustration at the end of this post.)

Shoulder impingement occurs when the rotator cuff is weakened or torn and cannot hold the humerus in its proper place when you lift your arm. As a result, the arm bone gets slightly dislodged and pinches the tendons and ligaments against another of the shoulder bones. This can cause a pinching sensation, pain or weakness when you raise your arm above your head.

Impingement can cause inflammation and swelling in the tendons. This narrows the space between the arm bone and the shoulder blade. As the space shrinks, the arm bone can’t rotate fully in the socket. It gets harder to lift your arm above shoulder level.

When impingement occurs suddenly, it’s usually a result of overworking your shoulder. If you are a professional baseball pitcher, you’re at high risk. (By the way, if you are, and if you’re really good, my Boston Red Sox need you as soon as your shoulder gets fixed!) But even if you’re just playing 18 holes of golf after a winter away from the course, you can develop the condition. Impingement can also develop slowly as tendons tighten with age or arthritis develops.

If your shoulder pain came on suddenly, try treating it with rest and ice. Avoid reaching overhead. But don’t immobilize your shoulder by wearing a sling. Apply ice packs every few hours to reduce inflammation. Over-the-counter medications like acetaminophen (Tylenol), ibuprofen (Advil, Motrin) or naproxen (Aleve) can help relieve pain.

The longer you have pain, the more likely it is that your shoulder movement gradually will become limited. Eventually you may not be able to lift your arm over your head. It’s called a “frozen shoulder.” Your doctor can refer you to a physical therapist. He or she will help you adjust your movements to strengthen your rotator cuff muscles and loosen the tendons and ligaments.

If you catch it early, shoulder impingement can usually be improved or cured. On occasion, surgery is required. When your condition is improved, you’ll look back in appreciation of all the things a healthy shoulder lets you do.

Anatomy of the shoulder joint

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Many shoulder injuries involve the shoulder’s main joint, where the humerus connects with the shoulder socket (called the glenoid) at the scapula.