Chronic pain in the front and center of the knee (anterior knee pain) is common among active, healthy young athletes-especially girls.

Causes
The complex anatomy of the knee is extremely sensitive to small problems in alignment, training and overuse. Pressure may pull the kneecap sideways out of its groove, causing pain behind the kneecap. In teenagers, a number of factors may be involved, such as inflexibility of thigh muscles that support the knee joint; knock-knees or abnormal hip rotation; and using improper sports training techniques or equipment. A direct blow can also cause pain behind the kneecap.

Symptoms
The pain usually begins gradually. There may be popping or crackling sounds in the knee when you climb stairs, or stand up and walk after prolonged sitting. Pain might flare up during activities that repeatedly flex the knee (i.e., jumping, squatting, running and other exercise) and at night. The knee may become swollen and tender. Without treatment, tendon strains and thigh muscle (quadriceps) weakness may develop. The knees could begin to buckle or give way from pain.

Treatment
Ice, rest and rehabilitation are the usual treatments for teenagers with pain behind the kneecap.
Ice: To relieve swelling and inflammation, apply ice wrapped in a towel to your sore knee a few times a day.
Rest: Stop doing whatever activities make your knee hurt. This probably means changing your training routine. You may need to learn proper exercise techniques. If you are obese, your doctor may recommend that you lose weight to reduce pressure on the knee. You may also benefit from using a simple knee sleeve with kneecap (patellar) cutout or strap, support devices (i.e., braces, shoe orthoses) and nonsteroidal anti-inflammatory medications for pain.

After the pain and swelling go down, you will probably need to regain range of motion, strength, power, endurance, speed, agility and coordination. Your doctor may prescribe an exercise program to normalize your thigh muscle and hamstring flexibility and strength, or recommend cross-training activities that emphasize stretching of the lower extremities.