Practice Essentials
Patellofemoral syndrome (PFS) is characterized by a group of symptoms that contribute to anterior knee pain and that often respond to conservative management. The pain is associated with positions of the knee that result in increased or misdirected mechanical forces between the patella and femur. [1, 2, 3] Lack of consensus regarding the cause of PFS remains, likely because several factors associated with the syndrome present differently in each patient. Arthroscopy helps to confirm the diagnosis of PFS by allowing direct visualization of the cartilage surface. The basic exercise principles for the management of the syndrome are improving the range of motion of the iliotibial band, hip flexors, and quadriceps; strengthening the core, quadriceps, hip abductors, hip extensors, and hamstrings; and restricting the offending physical activity.
Symptoms of patellofemoral syndrome
Knee pain is the most common presentation of PFS. The pain characteristically is located behind the kneecap (ie, retropatellar) and most often manifests during activities that require knee flexion and forceful contraction of the quadriceps (eg, during squats, ascending/descending stairs).
Diagnosis and management of patellofemoral syndrome
PFS is a clinical diagnosis based on history and physical examination. Plain film radiographs can assess the patella (kneecap) position. The anterior-posterior (AP) view shows the patella over the sulcus; the lateral view is imaged at 45º of knee flexion and in full extension to determine the height of the patella (ie, whether it is baja [low] or alta [high]). The sunrise view visualizes the patellofemoral articulation in the femoral condylar groove and can determine the tilt or angle of the patella, as well as demonstrate the depth of the intercondylar groove.
Advanced imaging studies such as computed tomography (CT) scanning or magnetic resonance imaging (MRI) are rarely needed but can be part of the diagnostic workup for refractory cases to ensure that there is no concurrent intra-articular disease or other contributing pathology. In addition, arthroscopic evaluation can provide assessment of joint structures that may cause symptoms that mimic PFS when they are impaired and allows for the direct visualization of the cartilage surface.
PFS responds well to a rehabilitation program. The initial treatment stage is designed to decrease pain, using modalities such as ice, analgesic medication, nonsteroidal anti-inflammatory drugs (NSAIDs), and activity modification. Patellar taping techniques are used in patients with PFS to reduce friction on the patella. A neoprene knee sleeve with the patella cut out is also helpful, as it provides proprioceptive feedback.
The rehabilitation treatment stage uses therapeutic exercise to restore flexibility, strength, and proprioception to the lower limb kinetic chain. Orthotics or appropriate footwear are sometimes recommended.
If PFS presents concurrently with knee pain secondary to degenerative changes and conservative measures fail, aspiration of effusion, along with injection of the knee joint with steroid or hyaluronic acid, may be tried. Surgical intervention for patellofemoral syndrome usually is in the form of arthroscopic evaluation followed by release of the lateral attachments of the patella. Most authors agree that surgical treatment rarely is indicated.
Pathophysiology
While theories regarding the pathophysiology of patellofemoral syndrome vary, identification of the resultant forces involved in dynamic and static knee positions has been fundamental to the research on this syndrome. Factors believed to contribute to production of retropatellar pain include impairments affecting the patellofemoral joint interface. Such impairments may result from an imbalance of ligamentous and muscle forces, malalignment between the joint surfaces, excessive knee valgus (ie, increased Q-angle) resulting in increased lateral forces, and quadriceps contractures causing production of excessive leverage forces on the patellofemoral joint surface. Excessive use of the joint, either in frequency of loading or excessive loading, also contributes to the symptoms.
Epidemiology
Frequency
Patellofemoral syndrome is estimated to be the most common cause of anterior knee pain in athletic and nonathletic populations.
United States
Patellofemoral syndrome is common in the United States, especially among physically active persons.
International
Patellofemoral syndrome has an estimated prevalence rate of 20% in student populations.
Mortality/Morbidity
Morbidity associated with patellofemoral syndrome is directly proportional to the activity level of the patient. Curtailing physical activities that place unnecessarily stressful demands upon the patellofemoral articulation may be necessary (preferably while substituting other activities into the exercise program).
Race
No racial predilection has been identified for patellofemoral syndrome.
Sex
Patellofemoral syndrome more frequently affects females than males.
Age
Patellofemoral syndrome occurs most frequently in adolescents and young adults.
