Monday, September 24, 2012

Patellofemoral pain

Patellofemoral pain, Managing patellofemoral pain syndrome is a challenge, in part because of lack of consensus regarding its cause and treatment. Contributing factors include overuse and overload of the patellofemoral joint, biomechanical problems and muscular dysfunction. The initial treatment plan should include quadriceps strengthening and temporary activity modification. Additional exercises may be incorporated as dictated by the findings of the physical examination. Footwear should be closely evaluated for quality and fit, and the use of arch supports should be considered. Patellofemoral pain syndrome can be defined as retropatellar or peripatellar pain resulting from physical and biochemical changes in the patellofemoral joint. It should be distinguished from chondromalacia, which is actual fraying and damage to the underlying patellar cartilage. Patients with patellofemoral pain syndrome have anterior knee pain that typically occurs with activity and often worsens when they are descending steps or hills. It can also be triggered by prolonged sitting. One or both knees can be affected. Consensus is lacking regarding the cause and treatment of the syndrome.1 Pathophysiology and Etiology The patella articulates with the patellofemoral groove in the femur. Several forces act on the patella to provide stability and keep it tracking properly A common misconception is that the patella only moves in an up-and-down direction. In fact, it also tilts and rotates, so there are various points of contact between the undersurface of the patella and the femur.2,3 Repetitive contact at any of these areas, sometimes combined with maltracking of the patella that is often not detectable by the naked eye, is the likely mechanism of patellofemoral pain syndrome. The result is the classic presentation of retropatellar and peripatellar pain. This pain should not be confused with pain that occurs directly on the patellar tendon (patellar tendonitis). Many theories have been proposed to explain the etiology of patellofemoral pain. These include biomechanical, muscular and overuse theories. In general, the literature and clinical experience suggest that the etiology of patellofemoral pain syndrome is multifactorial. OVERUSE AND OVERLOAD Because bending the knee increases the pressure between the patella and its various points of contact with the femur, patellofemoral pain syndrome is often classified as an overuse injury.4–8 However, a more appropriate term may be “overload,” because the syndrome can also affect inactive patients. Repeated weight-bearing impact may be a contributing factor, particularly in runners.3 Steps, hills and uneven surfaces tend to exacerbate patellofemoral pain. Once the syndrome has developed, even prolonged sitting can be painful (“movie-goer's sign”) because of the extra pressure between the patella and the femur during knee flexion. BIOMECHANICAL PROBLEMS AND MUSCULAR DYSFUNCTION No single biomechanical factor has been identified as a primary cause of patellofemoral pain,9,10 although many have been hypothesized. Some of the more popular theories are discussed in the following sections. Pes Planus (Pronation). The terms “flat feet” and “foot pronation” are often used interchangeably. Technically speaking, foot pronation is a combination of eversion, dorsiflexion and abduction of the foot. This condition often occurs in patients who lack a supportive medial arch (Figure 2). Foot pronation causes a compensatory internal rotation of the tibia or femur (femoral anteversion)11 that upsets the patellofemoral mechanism. This is the premise behind using arch supports or custom orthotics in patients with patellofemoral pain. Pes Cavus (High-Arched Foot, Supination). Compared with a normal foot, a high-arched foot provides less cushioning for the leg when it strikes the ground. This places more stress on the patellofemoral mechanism, particularly when a person is running.3 Proper footwear, such as running shoes with extra cushioning and an arch support, can be helpful. (It is preferable to purchase such footwear from a reputable athletic shoe store with knowledgeable staff.) Q Angle. Although some investigators believe that a “large” Q angle (Figure 3) is a predisposing factor for patellofemoral pain, others question this claim. One study12 found similar Q angles in symptomatic and non-symptomatic patients. Another study6 compared the symptomatic and asymptomatic legs in 40 patients with unilateral symptoms and found similar Q angles in each leg. Furthermore, “normal” Q angles vary from 10 to 22 degrees,3 depending on the study, and measurements of the Q angle in the same patient vary from physician to physician.13 Therefore, the physician should be wary of placing too much emphasis on such biomechanical “variants,” as this can lead patients to believe that nothing can be done about their pain. Muscular Causes. The potential muscular causes of patellofemoral pain can be divided into “weakness” and “inflexibility” categories (Table 1).3,4,6,7,9–11,14–23 Weakness of the quadriceps muscles is the most often cited area of concern. However, each potential cause should be evaluated and addressed appropriately to help guide conservative care. Treatment A review of the literature yields few quality randomized, controlled trials on the treatment of patellofemoral pain syndrome.1,24 Prospective long-term follow-up studies provide the most useful data.8–10,25,26 Until long-term randomized, controlled clinical trials are conducted, the treatment of patellofemoral pain syndrome must be guided by the available literature and clinical experience. EXERCISES AND PHYSICAL THERAPY Exercises for patellofemoral pain are based on the muscular causes listed in Table 1.3,4,6,7,9–11,14–23 Quadriceps strengthening is most commonly recommended because the quadricep muscles play a significant role in patellar movement. Hip, hamstring, calf and iliotibial band stretching may also be important. The decision to incorporate these additional exercises depends on an accurate physical examination. (Exercises used in the treatment of patellofemoral pain are illustrated in a patient information handout that follows this article.)
Title: Patellofemoral pain
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