About Patellofemoral Pain Syndrome
Patellofemoral pain, better known as “runner’s knee,” refers to a dull, aching pain under or around the patella (kneecap) where it articulates with the distal femur (thigh bone). This type of pain may occur in one or both knees, and tends to worsen with activity. The patella can move up and down, side to side, tilt and rotate against the femur. Overuse and/or overload of this mechanism can cause irritation to the cartilage on the underside of the patella. In later-stage cases, even prolonged periods of sitting can be painful due to the extra pressure between the patella and femur during knee flexion. The exact cause of patellofemoral pain is unknown, and is likely to be a combination of several factors.
Risk Factors
- Q Angle: The Q angle, or patellofemoral angle, is the angle between the quadriceps muscles (namely the rectus femoris) and the patellar tendon. This angle is determined by drawing a line from the anterior superior iliac spine (a prominent bone marking on the front of the hip) to the midpoint of the patella, and measuring the angle between this line and the vertical. Normal Q angles range from 13 to 18 degrees. Due to wider pelvic girdles, women tend to have higher Q angles than men. Larger Q angles are associated with a greater risk of knee and patellar problems. - Muscle Weakness or Imbalance: Because the knee is so central to the lower limb, imbalances and weaknesses in one or several of the muscle groups in the leg can lead to knee problems. Because of the close relationship of the quadriceps muscle insertion and the patella, weak quads can lead to poor knee tracking. Conversely, if the hamstrings are tight, more posterior stress may be placed on the knee and this can also lead to patellar pain. Some studies have even shown correlations between weakness in the hip muscles and patellofemoral pain. Finally, imbalances within any of the major muscle groups of the leg (such as the lateral quad muscle being stronger than the medial) can cause the patella to be pulled off center, leading to pain and irritation.
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| Excess movement of the patella can be caused by a number of factors. |
- Foot Pronation: Many overuse injuries of the lower limb can be linked, at least partially, to foot mechanics. Overpronation, or excess “rolling in” of the foot during weight bearing, is very common, but can cause problems all throughout the leg. When the foot and ankle roll in excessively, the tibia or femur may rotate internally to compensate. For this reason, overpronation can upset the patellofemoral mechanism, and is thought to be a contributor to patellofemoral pain syndrome.
- Athletics: Any one or combination of the aforementioned biomechanical risk factors may predispose an individual to patellofemoral pain syndrome. The risk goes up substantially if these factors are present in an athlete involved in any of the many sports that place a lot of stress on the knee joint. This includes, but is not limited to; running, jumping, skiing, cycling and soccer. Playing competitive sports is almost always a risk factor for overuse injury.
Treatment
- Rest: In the case of patellofemoral pain, all activities that induce symptoms should be stopped until the patient is pain free. Many athletes choose to take up non-weight bearing activities, such as swimming, to maintain fitness during recovery
- Ice and Anti-inflammatory Treatment: Applying ice for 10 to 20 minutes after activity can help reduce the pain and inflammation of patellofemoral pain syndrome, as can over the counter anti-inflammatory medications such as ibuprofen or naproxen. However, these medications should not be used over a long period of time, as they can have adverse side effects.
- Physical Therapy: Physical therapy is often the best treatment option for overuse injuries. Since so many biomechanical factors are thought to contribute to patellofemoral pain syndrome, physical therapy can provide exercises to strengthen more than one potential cause at a time. Often times, physical therapy for patellofemoral pain will focus on the quadriceps muscle groups. Physical therapists are able to test for muscle imbalances, and can tell which parts of the lower extremity need to improve in strength and/or flexibility. Regardless of whether or not these are the direct causes of patellofemoral pain, several weeks physical therapy and/or an at-home strengthening program, have been shown to be quite effective in treating knee pain symptoms.
- Proper Footwear/Orthotics: Since many common biomechanical factors can lead to patellar pain, braces, orthotic inserts, and proper footwear have been shown to provide relief in some patients. Certain knee braces and taping techniques have been shown to stabilize the patella. Orthotic inserts and proper footwear can correct exaggerated pronation patterns in the foot, which allows the entire lower leg to function more efficiently and can also prevent a multitude of other lower leg overuse injuries.
An Ounce of Prevention
Because the exact cause of patellofemoral pain is unknown, it can be difficult to prevent. However, there are a number of measures that can be taken to reduce the risk of nearly any lower limb overuse injury. Staying in shape and maintaining a healthy weight are often the first steps to preventing knee pain. Major leg muscle groups (such as quadriceps, hamstrings, hip abductors and adductors, etc.) should be strengthened equally to avoid muscle imbalances. With the onset of any new form exercise, the training load should be increased gradually. Individuals who overpronate, or have very high or low arches, should consult with a local running store to be properly fitted for running shoes, and older shoes should be replaced after 300-500 miles. It is also important to maintain proper running form during exercise, and in the case of knee pain, steep downhill runs should be avoided where possible.
Sources and Additional Information
American Academy of Orthopaedic Surgeons http://orthoinfo.aaos.org/
American Association of Family Physicians http://www.aafp.org/
Lippert, Clinical Kinesiology and Anatomy 4th edition.