"Patella" is a term for the kneecap – a flat triangular small sheet of bone in front of the knee. A patella moves as a knee bends. Knee movement is actually a coordinated motion that uses multiple bones simultaneously: the tibiofemoral (the tibia and femur, or thigh, bones) and patellofemoral (the patella and femur bones).

A healthy patella glides up and down the knee, supporting the front thigh muscles as the leg straightens. The patella acts as a protective shield to bones and tissues inside the knee.

Patellofemoral pain syndrome (PFPS) is characterized by pain in the front of the knee or around the kneecap, especially while walking up or down stairs or sitting for a long time. PFPS can also cause an inability to bend over or squat.

The condition can develop in one or both knees, and pain will increase or worsen with activity or after sitting a long time. About 2.5 million Americans experience symptoms of and are diagnosed with PFPS.

 

Causes of PFPS are mostly unknown. Medical experts suspect the pain has to do with the patella's movement over the thighbone (femur). They speculate the patella does not move smoothly or correctly when the knee bends or straightens, and that this incorrect movement can damage the underlying and surrounding tissues and cartilage. This damage causes pain.

Patellofemoral pain syndrome develops when pressure increases between the patella and femur, often when the knee has become overburdened while bending. PFPS is therefore extremely common in people who are active or play sports where pressure is increased on the knee, such as running and jumping hurdles. Having flat feet can also increase stress on the knee joint as the biomechanical alignment of the knee shifts, altering the movement of the patella.

Additionally, having a large femoral angle – the angle, sometimes called a "Q-angle," at which the thighbone intersects the knee – can cause PFPS. A large femoral angle can force the patella outside the knee, increasing pressure and damaging the knee's underlying structure, often painfully. Women are more likely to have PFPS than men because, generally, their pelvises are broader which creates a broader femoral angle. Additional causes include excessive athletic training, overusing a knee, malalignment of a kneecap, and tight, weak, or unbalanced thigh muscles.

Patients with PFPS may experience a dull ache or pain underneath the kneecap while walking, climbing up or down stairs, standing, or sitting for a long time. Sometimes, while trying to rise, a person's knee might catch and give a harsh, creaking sensation.

Pain in the knee will increase or worsen with intense activity. PFPS might be noticed or discovered while starting a new activity or increasing the intensity of an old one. Tenderness might occur in the inner side of the knee. Swelling might also occur after physical activity; however, swelling is not a major feature of PFPS.

Diagnosis

If a doctor suspects PFPS, he or she will ask many questions, including when the pain started and how the sensation feels, whether the patient has injured a knee recently, and about other health conditions such as diabetes or allergies (as these can affect a person's circulation and skin sensitivity, which might account for knee pain). The doctor will also ask about any medication the patient takes, which could influence his or her treatment.

The doctor will perform a physical examination, touching the kneecap and testing for pain and tenderness by moving its position and seeing how well the kneecap and legs flex and move. This examination is sufficient to confirm PFPS, but in rare cases a doctor might suggest running imaging tests to get a closer look before diagnosis. Imaging tests, such as an X-ray, will show the doctor if the kneecap is out of its track. Magnetic resonance imaging (MRI) scanning can detect whether the bone, cartilage, or muscle around the knee have been damaged and are causing pain. Another test, arthroscopy, involves putting a small camera on the edge of a long tube into the patient's knee to get a detailed look at the inner kneecap region.

The treatment options for PFPS include physical therapy, exercise, medications, surgery and more. Exercises for PFPS are prescribed when muscular damage is causing the pain. Usually exercises that strengthen the quadriceps (the largest extensor muscles in the legs) are recommended; quadriceps play an important role in patella movement. Additional exercise regimens might vary, depending on the doctor's diagnosis during the initial examination. Twenty minutes of exercise everyday is often sufficient for treating PFPS.

Anti-inflammatory drugs have proven largely ineffective for treating PFPS because their side effects outweigh benefits. The best anti-inflammatory treatment is icing a swollen or painful knee for 20 to 30 minutes after physical activity. Because one cause of PFPS is overusing the knee, reducing intensity and frequency of activity can reduce its symptoms. Additionally, taping the kneecap into a perfect position will help reduce friction and pain during knee movement. Many patients have found walking and athletic footwear effective in curing PFPS. In extremely rare case, surgery can smooth the undersurface of a patient's patella to allow better movement.

No PFPS treatment works over night. Treatment typically takes at least six weeks for the condition to improve. PFPS is less likely to return if a patient follows his or her physical therapy regularly. Some exercises that can relieve PFPS pain include:

Straight-leg raises: A patient lies on his or her back, fixing his or her good knee in a bent position, while keeping the affected knee straight. The patient then raises his or her affected knee into the air, holding a few seconds before releasing, resting, and repeating. (Three sets of 15 repetitions.)

Hip adduction: A patient lies on his or her side with the affected leg on the bottom. He or she positions the good leg in back or front of the affected one and then tries to raise the bad knee and hold for a few seconds. (Three sets of 15 repetitions.)

Hip abduction: A patient lies on his or her side again. This time, the affected leg is on top. The patient bends the good leg, keeping the bad one straight. He or she tries to lift the bad leg toward the ceiling and hold a few seconds. Neither the hip nor body should lift; the patient should not roll onto his or her stomach either. (Three sets of 15 repetitions.)

Hip flexion: A patient sits straight on the edge of a chair or table, knees hanging down. He or she lifts the affected knee toward the ceiling, holds a few seconds, and then lowers. (Three sets of 15 repetitions.)

Hamstring: (This stretches the posterior thigh muscles.) A patient sits on the floor with his or her legs stretched out. He or she reaches to touch the toes with a finger, while keeping his or her back straight and holding the position for 30 seconds. (Five repetitions.)

Quadriceps: (This strengthens the anterior thigh muscles.) A standing patient bends his or her affected leg backwards, pulling the ankle with a hand. The patient should try to touch his or her foot to the buttocks and hold for 30 seconds. He or she might need to balance by holding a chair or wall. (Five repetitions.)

Gastrocnemius/soleus: A patient leans against a wall with both hands for 30 seconds. This stretches his or her calves. After 30 seconds, the patient bends his or her knee, which stretches the soleus muscle, located in the lower part of the calf, for 30 seconds.

Iliotibial band: (The iliotibial band runs from a hip to the knee on the outside of a leg.) A patient sits on a floor or mat with both legs stretched out. He or she crosses one leg over the other. The hand opposite the crossed leg grips the crossed leg while the patient pulls his or her body; the torso should twist so that the opposite shoulder touches the knee.

These exercises, though simple, can relieve much of the pain from PFPS.

Outlook

Knee pain is a common problem facing millions of people around the world. Often, people who have PFPS are wrongly diagnosed with or treat themselves for arthritis. In order to prevent or treat PFPS, knowing its symptoms and signs can help by preventing false diagnosis and treatment. A patient should always consult his or her doctor to learn the proper cause of knee pain and direct his or her treatment toward curing the condition and its symptoms.