Patellofemoral syndrome (PFS), sometimes referred to as patellofemoral pain syndrome and chondromalacia patella, is a disorder characterized by thinning, softening, and breaking down of the cartilage located on the back side of the patella (kneecap) and/or on the medial (inner) or lateral (side) femoral condyles; pain and inflammation from synovial fluid that lubricates the lining of the knee joint and its tendons; and general deterioration in the distal femur or patella. PFS is a condition involving damage to the cartilage under and around one or both kneecaps that becomes worse when active or when getting up after being sedentary for a long time. It is frequently the result of sports injuries.
Patellofemoral is a term that incorporates the words patella, the medical name for the kneecap, and femoral that refers to the thigh and, specifically, the femur (the main bone in the thigh). The patellofemoral joint is one of the joints of the knee. It is formed by the kneecap and the femur.
The main knee joint connects the thigh bone and the shin bone (tibia). The knee joint is surrounded by a capsule containing ligaments that loop around the inside and outside of the joint (collateral ligaments), along with cruciate ligaments that cross within the joint. These ligaments provide the knee joint with stability and strength.
The kneecap is positioned over the front of the knee joint. Tendons—specifically, the patellar tendon that attaches the kneecap to the shin and the quadriceps tendon that attaches the thigh muscles to the top of the kneecap—attach the kneecap to the bones and muscles that surround the knee. As the knee moves, the underside of the kneecap slides over the knee bones. PFS can occur then the kneecap loses this normal motion as it begins to grind against the lower part of the thigh bone.
PFS is frequently diagnosed in people participating in sports that have high impact to the knees, such as basketball, handball, racquetball, and volleyball— specifically, sports that involve a lot of running, jumping, sudden stopping, and twisting. These activities place abnormally high stress onto the knees. A change of physical activity, such as its intensity or the sport itself, may also contribute to increased risk of PFS. PFS is most often found in adolescent and young adult athletes, and is more likely to occur in females than in males. The Mayo Clinic states that PFS is twice as likely to occur in women than it is in men—possibly because the wider pelvis in the female frame increases the angle in which the bones of the knee joint meet.
The exact cause of PFS is not known. However, the medical community does know that abnormal forces on the knee joint and/or prolonged repetitive stress on the knee joint (specifically, compressive or shearing stresses [forces]) can likely lead to the syndrome.
PFS is often a frequent result of pain in the back of the knee (anterior knee pain). Causes of PFS include:
Once one or more of these causes occur, the following can also result:
Symptoms of PFS include a grating or grinding feeling when the knees are bent, along with a dull, aching pain in the front of the knee and tenderness around the knee. Swelling of the knee usually does not occur. The most common symptom is knee pain that increases when walking up or down stairs. Localized pain in the front of the knee often occurs when:
If such symptoms do not improve or go away after a few days of experiencing them, then a visit to the doctor is recommended. Upon an examination by a family doctor or other such general practitioner, a physical therapist, sports medicine specialist, or orthopedic surgeon may be recommended.
A physical examination of the knee is performed by a physician. X-rays, computerized tomography (CT) scans, or magnetic resonance imaging (MRI) scans may be taken of the knee. X-ray scanning effectively shows the bones, and to a lesser degree the tissues around the knee. CT scans involve x-rays taken in many different angles to create a three-dimensional image of the knee's structure. Such a technique is a much better way (when compared to x-ray scans) to visualize both bones and soft tissues. MRI scans use radio waves (a form of electromagnetic radiation) and a strong magnetic field to produce exact images of the bones and tissues of the knee.
During the exam, the doctor examines different parts of the knee and moves the leg into various positions to analyze the extent of the pain and other symptoms. Besides eliminating other problems, the examination, along with the various scans taken, help the physician understand how to better treat the injury if all the signs point to PFS.
Initially, the knee should be rested until the pain disappears. Pain relievers, such as acetaminophen (Tylenol), and nonsteroidal anti-inflammatory drugs (NSAIDs), such as aspirin (acetylsalicylic acid) or ibuprofen (Advil, Motrin), should also be taken to reduce pain immediately after exercising. Apply ice for 10–20 minutes to reduce inflammation. The R.I.C.E. (Rest, Ice, Compression, and Elevation) treatment reduces the pain and discomfort and helps to shorten the recovery process.
For those with worsening pain from sitting too long, periodically straighten the leg. Individuals who are overweight or extremely overweight (obese) should begin a weight loss program that will help to place less stress onto the knees.
Physical therapy may be recommended, including rehabilitation exercises. These exercises stretch and strengthen the muscles of the knees and help them to properly realign themselves. Other exercises help areas positioned away from the knee but still important for knee health. Some of the recommended exercises include those for the quadriceps (especially the front quadriceps), back (hamstrings), calf, and hips (especially the hip abductor muscles and the iliotibial band, near the hip joint). Strengthening the hip abductor muscle has been medically shown to decrease both pain and joint problems within the knee. In addition, strengthening the quadriceps helps to stabilize the kneecap. Overall, strong muscles help to correct problems with the knee. Proper flexibility of the muscles is also important to reduce the risk of getting PFS.
Exercise is important to strengthen muscles around the knee. Until symptoms disappear or reduce, stop performing high-impact exercises and physical activities such as running. Nonimpact or low-impact exercises (sometimes called “knee-friendly” activities) such as aerobics, bicycling, swimming, and walking should be substituted. The use of elliptical trainers or similar machines are excellent ways to get a workout without introducing high forces onto the knees.
If running is continued, it is better to run on a smooth, soft surface (such as a running track) than on a hard surface (such as concrete or asphalt). It is also better to walk down slopes rather than running up them. Once the pain has subsided, slowly return to normal activities by increasing the amount of time by no more than about 20% per week.
Supportive braces, arch supports, custom orthotics, tape, and other external measures can be worn to help protect and stabilize the knee joint and improve the alignment of the kneecap. In addition, such external measures may help to prevent future injury. A physical therapist can provide proper instruction on how to use such devices. Shoe inserts help to provide extra support to cushion impacts onto the knees. This is especially true for people with flat feet. When exercising, especially for running and other high-impact activities, make sure the athletic shoes are made of quality materials, fit comfortably, and have sufficient cushion. Discuss shoes and shoe inserts with a doctor because proper footwear can reduce the impact on the knees.
PFS is difficult to treat and is usually not resolved in the short term. It may take six weeks or longer for the knee to improve to any noticeable degree. However, it usually improves with treatment in the long term. In a small percentage of cases—when symptoms and pain are not reduced or eliminated—surgery may be necessary.
Two types of surgery for the knee are arthroscopy and open surgery. Arthroscopic surgery involves the insertion of an arthroscope, a thin device with a camera and light that goes into the knee through a tiny incision in the skin. The surgery involves various procedures, such as removing fragments of damaged cartilage, that improve the condition of the knee. Open surgery may be performed in more serious cases, such as when the knee must be realigned. When performed, surgery usually resolves the problem. However, in a small number of surgical cases, infection may occur, along continuation of the pain, or even a worsening of the symptoms.
The knee is less likely to be injured with PFS if the entire body is in good shape and muscles remain strong. Attention to strong muscles, in order to keep the knee properly balanced and aligned during exercise, resides primarily with the hip abductor muscles and quadriceps. Asking a family doctor or physical therapist for a list of recommended exercises that can build flexibility and strength into the muscles, especially those that are used for running, jumping, moving from side to side, squatting, and stepping down, will help minimize the potential for injuries. Regular exercise is a good preventive measure to avoid hurting the knee.
Always warm up with light exercises (walking, stretching, etc.) for at least five minutes before doing any type of exercises or activities. Stretching is important to add flexibility to the muscles before exerting them. Caution should be used when performing high-impact sports. Overexertion in such sports or making drastic changes in the intensity of workouts should be avoided. Instead, if changes occur, do them gradually over a long period. Make sure proper footwear is used, and that shoes fit well and provide adequate shock absorption.
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American Association of Orthopaedic Surgeons, 9400 W Higgins Rd., Rosemont, IL, 60018, (847) 823-7186, (800) 626-6726, Fax: (847) 823-8125, firstname.lastname@example.org, http://www.aaos.org .
American Pain Society, 8735 W Higgins Rd., Ste. 300, Chicago, IL, 60631, (847) 375-4715, email@example.com, http://americanpainsociety.org .
William A. Atkins, BB, BS, MBA