Carlos Moffatt, age 11, of Tucson, Ariz., for his question:

HOW DO YOU DEVELOP TENNIS ELBOW?

Excessive or violent twisting of the forearm may injure the elbow ligaments or the synovial capsule. This type of injury is sometimes called tennis elbow because it often results from playing tennis.

A capsule or pouch of tough connective tissue surrounds the elbow joint. This capsule and several strong cordlike tissues called ligaments hold the bones in place. Synovial fluid in the capsule usually reduces friction at the elbow.

An elbow joint can become dislocated if a person falls on his outstretched arm.

An elbow connects a person's upper arm with his forearm. The humerus    the bone of the upper arm    and the radius and ulna    the two bones of the forearm    meet at the elbow.