Patellofemoral syndrome is a very common condition and is characterized by pain typically behind or under the knee cap (patella) arising from the joint between the knee cap and the thigh bone. One or both knees can be affected. Patients with patellofemoral pain syndrome have anterior knee pain that typically occurs with activity and often worsens when they are descending steps or hills. It can also be triggered by prolonged sitting and long periods of inactivity.
Although the exact cause of patellofemoral pain is unknown, it is likely associated with the way the knee cap moves or tracks along the groove of the thigh bone. As the knee bends the patella should slide smoothly along this groove. However, there are forces that can be placed on the knee cap that may cause the knee cap to push against the sides of this groove resulting pain. Some possible causes of patellofemoral syndrome include overuse/overload, biomechanical problems and muscular dysfunction.
Causes:
•    Overuse/overload
•    Repetitive bending and straightening of the knee that occurs in running
•    A constant bending motion, especially on the weighted leg
•    Biomechanical problems
•    Patella tracking
•    Tightening of the knee cap, losing its normal ability to move in many directions.
•    Flat feet
•    High arches
•    Muscular dysfunctions
•    A weakness or strength imbalance of the quadriceps muscles may alter the tracking of the patella.
•    Tight muscles and tendons may also affect patella tracking.
Signs and Symptoms:
•    Generalized pain around knee cap
•    Pain with running, going down stairs or hills, squatting
•    Pain with bending of knee
•    Crepitus (a crackling noise under knee cap with movement)
Benefits of physical therapy:
•    Decrease knee pain
•    Increase strength of quadriceps and hamstrings
•    Increase flexibility
•    Decrease swelling
Treatment for patellofemoral pain consists of resting, icing, stretching, activity modification, and anti-inflammatory medication. One may also seek treatment from a physical therapist to assist in the treatment process. An exercise program provided by your physical therapist will include strengthening of the muscles around the knee such as the quadriceps. Strengthening the quadriceps muscles will be very important because they play a major role in the function of the knee cap. The healing time for patellofemoral pain varies from person to person and can be between six weeks to six months. If you continue to experience patellofemoral pain after conservative treatment, surgery may be recommended, although this is fairly uncommon.