Dislocated patella associated with below-knee amputation in adolescent patients.

One-third of the adolescent patients followed up in our prosthetic clinic have developed patellar dislocation. Four cases are described, and radiographs are evaluated for femoral-tibial alignment, patellar height, and tibial length. Patella alta was present in each patient. We propose that the forces associated with the patellar tendon-bearing prosthesis may produce elongation of the patellar tendon in young patients and predispose them to patellar instability.