Knee pain in front of the knee in young people is becoming common.Knee cap (Patella) is a small bone which lies in front of lower end of thigh bone (Femur). The back side of knee cap is lined by smooth tissue called cartilage. This covering helps the patella to glide in a groove on the lower end of thigh bone. The knee cap is held on the top by thigh muscles (Quadriceps) and lower part is connected to the shin bone by Patellar tendon. Function of knee cap is to aid knee movement and stabilize knee joint while walking.