Brian Parlier, age 11, of Gastonia, N.C., for his question:

WHAT IS TENNIS ELBOW?

When the motion of straightening the elbow is overdone, such as in playing tennis, a bursa between the upper arm and forearm becomes inflamed, resulting in the condition called radiohumeral bursitis, or tennis elbow.

If you had tennis elbow, there would be a throbbing pain in your forearm near the elbow, on the thumb side of your arm. The pain is worse when the wrist is bent backward, as in making a fist or picking up a small object.

Oddly enough, lifting a large object doesn't heighten the pain because the wrist does not bend backward during this action.

Much of the pain and discomfort of bursitis is caused by calcium deposits.