Last updated: 11/24/2009

A person of any age can break a kneecap in an accident. When the bone is shattered beyond repair, the kneecap has to be removed. No prosthesis or artificial replacement part is put in its place.

Dislocation of the kneecap is most common in young...

girls between the ages of 10–14. Initially, the kneecap will pop back into place of its own accord, but pain may continue. If dislocation occurs too often, or the kneecap does not go back into place correctly, the patella may rub the other bones in the knee, causing an arthritis-like condition. Some people are also born with birth defects that cause the kneecap to dislocate frequently.

Degenerative arthritis of the kneecap, also called patellar arthritis or chondromalacia patellae, can cause so much pain that it becomes necessary to remove the kneecap. As techniques of joint replacement have improved, arthritis in the knee is more frequently treated with total knee replacement.

People who have had their kneecap removed for degenerative arthritis and then later require a total knee replacement are more likely to have problems with the stability of their artificial knee than those who only have total knee replacement. This occurs because the realigned muscles and tendons provide less support once the kneecap is removed.