The tendon (patella tendon) from the thigh muscle (quadriceps) crosses over the kneecap (patella) and connects with the lower leg (tibia).
Irritation can occur where the tendon attaches to the lower edge of the kneecap. Although the cause of the irritation is unknown, it occurs with repeated jumping in sports such as volleyball or basketball. This problem is thus called “jumper’s knee.”
Jumper’s knee causes pain at the front of the knee, during or after exercise. Pressure just below the kneecap causes pain, as well. Sometimes the upper or lower edge of the kneecap is also sensitive when pressed.
Image 1: Jumper's Knee (Patellar tendonitis)