Patellofemoral pain syndrome: evaluation and treatment
Section snippets
Terminology
Patellofemoral pain is a descriptive term that simply means pain coming from the area of the patellofemoral joint. The patellofemoral joint is composed of supporting structures in addition to patella and femur. In fact, the pain usually originates from these supporting structures, and for this reason the term anterior knee pain is often used interchangeably with patellofemoral pain. Both anterior knee pain and patellofemoral pain syndrome should be distinguished from chondromalacia, which is
Epidemiology of patellofemoral pain
Patellofemoral pain syndrome is one of the most common disorders of the knee, and affects athletes and nonathletes alike. It accounts for 30% of all injuries seen in a sports medicine clinic [8]. Nine percent of young athletes [9] and 15% of military recruits [10] report patellofemoral pain. Females experience anterior knee pain more often than males, with incidence rates of 10% in young female athletes, and 7% in young male athletes [9]. Patellofemoral pain accounts for 33% of all knee
Anatomy and biomechanics of the patellofemoral joint
The most important function of the patella is to facilitate knee extension. The patella increases the force of knee extension by up to 50% [12]. The patella also functions to centralize the divergent forces of the quadriceps and to transmit this force evenly to the patellar tendon and the underlying bone. The patella also protects the patellar tendon from friction by holding it away from the femur. The patella undergoes changes in tilt, rotation, and medial–lateral position as the knee goes
Anatomic sources of anterior knee pain
Histologic studies show that nerve fibers capable of transmitting pain are found in the retinaculum, patellar and quadriceps tendons, synovium, fat pad, and subchondral bone [31], [32], [33], [34], [35], [36], [37]. Hyaline cartilage is devoid of nerve fibers [38]; therefore, superficial defects in the chondral surface do not directly cause pain. This was demonstrated in an interesting experiment in which the primary investigator underwent knee arthroscopy without intra-articular anesthesia.
Mechanism of injury
The three main mechanisms responsible for patellofemoral pain are trauma, overuse, and abnormal patellar tracking, all of which can lead to increased strain on the peripatellar soft tissues, increased patellofemoral joint stress, or both. In many cases the mechanism of injury is multifactorial.
Risk factors
Several factors may increase the risk for patellofemoral pain by increasing patellofemoral joint stress, altering patellar tracking, or both.
Diagnosis
A thorough history and targeted physical examination will confirm the diagnosis of patellofemoral pain syndrome, locate the anatomic source of the symptoms, and identify all of the contributing risk factors. A precise diagnosis is essential to designing the optimal treatment program.
Nonoperative treatment
Nonoperative treatment can include one or more of the following interventions: rest, physical therapy with patellar taping and biofeedback, nonsteroidal anti-inflammatory medications (NSAIDs), shoe orthoses, knee sleeves, a resistive knee brace, acupuncture, and intra-articular and intramuscular injections of glycosaminoglycan polysulfate. Nonoperative treatment is successful in 75% to 84% of cases [72], [111], and prognosis is optimized when treatment is tailored to the specific findings on
Prognosis
Although nonoperative treatment eliminates symptoms in better than 75% of patients [11], [51], [72], [133], 70% experience a return of symptoms within 12 months [8], [126], [134]. Long-term studies have found persistent pain in 50% to 94% of subjects 6 to 8 years after presentation [10], [98]. Several studies have attempted to identify the factors that predict prognosis. Patients who reported the largest improvements with physical therapy tended to have more pain and disability at baseline, as
Surgical treatment
Arthroscopy can be helpful in understanding the etiology and pathophysiology of anterior knee pain in patients who do not respond to conservative management [136]. Surgical treatment can include excision of a painful medial synovial plica or retinacular neuroma [43], [137]. Synovectomy may be helpful in a patient who has chronic synovial inflammation. Patients who evidence lateral patellar compression syndrome may benefit from a lateral retinacular release. Some patients may also require
Summary
Patellofemoral pain syndrome is common among athletes and nonathletes. It results from an imbalance of forces acting on the patellofemoral joint, which leads to increased strain on the peripatellar soft tissues, increased patellofemoral joint stress, or both. The most important risk factors are overuse, quadriceps weakness, and soft-tissue tightness. In most cases, the etiology is multifactorial. A careful history and targeted physical examination will confirm the diagnosis and determine the
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Formerly at Center for Athletic Medicine, Chicago, Illinois, USA.