What Is Patellofemoral Pain Syndrome?

Patellofemoral pain syndrome (PFP syndrome) is pain in and around the kneecap (patella). PFP syndrome is also called "runner's knee."

Rest and exercises that stretch and strengthen the hips and legs can help PFP syndrome get better.

What Causes PFP Syndrome?

Patellofemoral (pronounced: peh-tel-oh-FEM-er-ul) pain syndrome is an overuse disorder. These happen when someone does the same movements that stress the knee over and over again.

In PFP syndrome, repeated bending and straightening the knee stresses the kneecap. It's most common in athletes.

Some people with PFP syndrome have a kneecap that is out of line with the thighbone (femur). The kneecap can get out of line, or wiggle as it moves along the thighbone, because of muscle weakness, trauma, or another problem. If this happens, the kneecap doesn't glide smoothly over the thighbone when the knee bends and straightens. The kneecap gets injured and this causes the pain of PFP syndrome.

Who Gets PFP Syndrome?

Patellofemoral pain syndrome usually happens in people who do sports that involve a lot of knee bending and straightening, such as running, biking, and skiing. It also can happen to people, particularly young women, who do not do a lot of sports.

PFP syndrome is more common in women and happens most often to teens and young adults.

Tight or weak leg muscles or flat feet can make someone more likely to get PFP syndrome.

What Are the Signs & Symptoms of PFP Syndrome?

Patellofemoral pain syndrome causes pain under and around the knee. The pain often gets worse with walking, kneeling, squatting, going up or down stairs, or running. It may also hurt after sitting with a bent knee for a long time, such as in a long car ride or in a movie theater.

Some people with PFP syndrome feel a "popping" or creaking after getting up from sitting or when going up or down stairs.

How Is PFP Syndrome Diagnosed?

To diagnose patellofemoral pain syndrome, health care providers:

• ask about physical activities
• do an exam

Usually no testing is needed. Sometimes the health care provider orders an X-ray or other imaging study to check for other knee problems.

How Is PFP Syndrome Treated?

Someone with patellofemoral pain syndrome needs to limit or completely avoid activities that cause pain. Sometimes a change in training is all that's needed. For example, someone who usually runs hills to train can try running on a flat, soft surface instead. 

A person who has severe pain or pain that interferes with activity (for example, if it causes a limp) needs to rest the knee until the pain is better.

For pain:

• Put ice or a cold pack on the knee every 1–2 hours for 15 minutes at a time. Put a thin towel between the ice and your skin to protect it from the cold.
• You can take ibuprofen (Advil, Motrin, or store brand) or naproxen (Aleve, Naprosyn, or store brand). Follow the directions that come with the medicine for how much to take and how often. Do not take this medicine for longer than about 2–3 weeks.

An important part of the treatment for PFP syndrome is improving the strength and flexibility of the legs, hips, and core muscles. Health care providers usually recommend going to a physical therapist to make an exercise plan that will help. The plan may include stretching, squats, planks, lunges, and other exercises that improve strength and flexibility of the legs and hips.

The health care provider might also recommend:

• a knee brace
• taping of the knee
• special shoe inserts

It doesn't happen very often, but sometimes surgery is needed for PFP syndrome.

Can Someone With PFP Syndrome Play Sports?

Most people with PFP syndrome need to cut back or stop sports for some time. Follow the health care provider's instructions on when it's safe for you to go back to sports. This usually is when:

• Hip, leg, and core strength is near normal.
• Flexibility, especially in the hamstring muscle, has improved.
• There's no pain with everyday activities, such as walking and going up/down stairs.
• Any pain with activity is very mild and goes away within a few minutes of starting the activity.

Looking Ahead

It can take months to years for the symptoms from PFP syndrome to get better. Following an exercise plan given by the health care provider or physical therapist can help the knee heal.

To lower the stress on their knees after healing, athletes should:

• Warm up and stretch before running or other sports.
• Keep a healthy weight.
• Wear supportive running shoes and replace them often.
• Run on soft, flat surfaces (such as grass, dirt, or a synthetic track with a softer surface).
• Increase the intensity of workouts slowly.
• Use shoe inserts or a knee brace, if the health care provider recommends it.