Chondromalacia of the knee, or patello-femoral pain, is a common cause of knee pain in young athletes. This is most often seen in athletes who are engaged in competitive running and jumping activities. The athlete experiences pain in the front of the knee around the kneecap (patella), worse when going up and down stairs, sitting, squatting, jumping, or kneeling. In many cases, there is associated stiffness with the quadriceps muscle.

Patello-femoral pain can be corrected with appropriate exercises, which include stretching and strengthening in such a way that does not cause more pain. This rehab program, under the supervision of a physical therapist, improves the function of the kneecap in its contact with the femur. Patello-femoral bracing, anti-inflammatory medication, and ice also help relieve the pain and allow the athlete to rehab effectively and return to sport.

Instability of the kneecap is a severe variation of patellofemoral pain, in which the kneecap may dislocate completely or partially (subluxate). Physical therapy is prescribed for patellar instability, although many athletes may require surgical treatment.

When adolescents experience pain about the knee severe enough to limit athletic achievement or enjoyment, a medical evaluation is needed.