I work as a medical transcriptionist. Lately I’ve been typing the notes for an orthopedic surgeon who treats mostly children. She often refers to joint mice. What does this refer to?

Fragments of cartilage or bone that have come loose in a joint are sometimes called joint mice. This name comes from the fact that the joint makes a squeaking sound as these pieces crunch against each other or rub against the bone.

The most common cause of joint mice is osteochondritis dissecans (OCD). OCD is a painful condition within a joint. The loose fragments inside the joint set up an inflammatory response that can be very painful.

Children and adolescents between the ages of five and 14 are affected most often. Overuse, repetitive use, and trauma are the usual underlying causes of the problem. The elbow in baseball pitchers and gymnasts is affected most often.