Patellofemoral pain syndrome

Medical quality assurance by Dr. Albrecht Nonnenmacher, MD at August 1, 2016
StartDiseasesPatellofemoral pain syndrome

Patellofemoral pain syndrome (PFPS) refers to pain originating from the front of the knee around the patella (also known as the kneecap). No one specific cause is associated with patellofemoral pain syndrome, but it is sometimes referred to as runner's knee because it frequently results from participation in sports that involve running and jumping.

Contents

Definition & Facts

Patellofemoral pain syndrome is a common sports injury in the United States, especially among teenagers, young adults, and those who are physically active or who perform manual labor. It is defined as a type of knee pain originating from above, below, in front of, or behind the patella or kneecap. Treatment commonly includes RICE (medicine). Rest, ice, stretching exercises, and physical therapy to strengthen the quadriceps femoris muscles are used to treat the syndrome.

Two terms, patellofemoral pain syndrome and chondromalacia patellae are sometimes used interchangeably to describe the same syndrome, but the latter technically refers to a condition involving damage to the patellar articular cartilage. This cartilage covers the back of the patella, the end of the femur or thighbone, and the trochlear groove, a small groove at the end of the thighbone where the patella is located. The patellar articular cartilage provides a slippery surface that allows the patella to glide easily up and down the trochlear groove as the knee bends or straightens. Patellofemoral pain syndrome does not involve damage to the cartilage. 

Symptoms & Complaints

The pain from patellofemoral pain syndrome ranges from a mild to a severe ache felt in the front of the knee. Stiffness and some swelling may accompany the pain. On occasion, the knee may suddenly buckle and fail to support weight.

Other symptoms include a popping or grinding sensation in the knee or a catch in the knee as it moves. Those suffering from patellofemoral pain syndrome may place a hand over the front of the knee or draw a circle around the knee to indicate the location of the pain. 

Prolonged periods of sitting or squatting as well as jumping, climbing up or down stairs, or walking up and down a slope, such as walking or hiking on a hillside, may produce symptoms or make them worse. Descending a flight of stairs or a slope is more likely to produce symptoms than ascending. 

Causes

Patellofemoral pain syndrome does not have a single specific cause. It is associated with injuries to the knee, with overuse, and with problems that interfere with the smooth movement of the patella within the trochlear groove. Injuries can result from falls that impact or twist the knee. Knee injuries also result from lifting objects that are too heavy or from not using the correct technique for lifting a heavy object. 

Overuse of the knee can result from an increase in or sudden change in physical activity that requires the knee to absorb more force or a higher number of impacts. Activities that require the knee to absorb more force include beginning weightlifting, increasing the weight you lift during exercise or at work, or increasing the number of times you lift weight during exercise or at work.

Increasing the number of aerobic activities or the duration of aerobic activities increases the number of impacts the knee must absorb. Aerobic activities that result in impact include stair climbing, running, jogging, dance exercise, and sports such as basketball, soccer, football, and tennis.

Incorrect exercise, weightlifting, or lifting techniques; incorrect use of exercise equipment; switching footwear; or changing to a different surface for running, jogging, or playing sports can also lead to patellofemoral pain syndrome. 

Problems that interfere with the smooth movement of the patella include misalignment of the legs between the knees and the hips and weakness in the leg muscles or an imbalance in the strength of one set of muscles over the other, especially when the quadriceps muscles are weak. These problems cause the patella to push out to one side or the other of the trochlear groove instead of gliding up and down in the center of the groove. 

Diagnosis & Tests

Diagnosis includes questions about type and severity of the pain and its location, when the pain began, activities that make the pain worse, general health, past knee injuries, and recent activities that may have caused patellofemoral pain syndrome to develop.

During the physical examination, the doctor may gently guide the knee into various positions, gently press and pull on the front of the knee and the patella, test core body strength, and test the knee with requests to jump, squat, lunge, and walk.

Most often the doctor will make a diagnosis on the basis of the physical examination and the answers to the questions. However, the doctor may order an X-ray, a CT scan, or a magnetic resonance imaging (MRI) test to rule out chondromalacia patellae.

Treatment & Therapy

Treatment may be as simple as RICE -- rest, ice, compression, and elevation. The doctor may recommend arch supports or a supportive brace for the knee, but wrapping the knee with an elastic bandage may provide enough support. A nurse or physical therapist can demonstrate the proper way to wrap the knee.

Usually over-the-counter pain medications such as ibuprofen, acetaminophen, or naproxen sodium are sufficient to ease the discomfort. A physical therapist will suggest exercises to strengthen and stretch the quadriceps, hamstrings, and hip abductors. These muscles control the alignment of the leg and support the knee. If exercise does not sufficiently improve alignment, surgery may be needed to remove pressure on the cartilage and properly align the patella. 

Prevention & Prophylaxis

Performing exercises that strengthen and stretch the quadriceps, hamstrings, and hip abductors enable them to continue to support the knee and maintain proper alignment of the leg.

In addition, always warming up and stretching before and after participating in sports and aerobic activities, and increasing the level of activity gradually can reduce the risk of patellofemoral pain syndrome and other knee injuries and sports injuries writ large.

Wearing the correct footwear for the activity and making sure the shoes are properly fitted are important preventative approaches. Using the correct technique when exercising or lifting heavy objects, reducing activities that have resulted in previous knee injuries, and seeking to achieve and maintain a healthy body weight to reduce stress on the knee, can all help prevent patellofemoral pain syndrome.