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The consensus statement (2016) defines PFP as pain presenting behind or around the kneecap that is provoked by at least one activity that stresses the PFJ while weight-bearing on a flexed knee. The aggravating activities include: climbing stairs, squatting, running and jumping. However, the term PFP was previously used interchangeably with chondromalacia patellae, but the latter refers to the softening of articular cartilage detected on MRI and arthroscopy. On the other hand, structural defects are not present in PFP and investigations are not required for making a diagnosis of PFP.(1)
The cardinal feature for PFP is peri patellar or retro patellar pain or stiffness provoked by prolong sitting with knee flexed (movie sign).(1) That condition is commonly found in athletes and physically active individuals. Its impact is significant, frequently decreasing the sport performing abilities.(2) As a matter of fact, a number of recreational athletes quit their sport, due to PFP.(3) The annual prevalence of PFP in adults is almost 23% and roughly covers 29% of the adolescents in the general population. 36% of the professional cyclists are affected by PFP.(4)PFP affects physically active persons and account for 25 to 40% of all knee complains examine in a sports injury setting.(5) Females are 2.23 times more likely to develop PFP than male counterparts.(6) Its occurrence varies from 22 newly discovered cases per 1000 individuals per year in highly active population to 5-6 newly discovered cases per 1000 individuals in general practice.(7)
Painful symptoms associated with this condition decreases the level of physical activity and limit participation in athletic events.(4) PFP is the preferred terminology used for diffuse anterior knee pain.(2) In the UK there are approximately more than 100 million primary care appointments per day for musculoskeletal disorders. On the other hand there are almost 126.6 million citizens affected from musculoskeletal disorder in the US. In above all musculoskeletal related disorders, knee pain is the second most prevalent condition, with PFP is considered one of the most common reason of knee pain. The cited prevalence lies between 15 to 45%.(8) PFP has increase prevalence in orthopaedic, general practice and sports medicine. The condition starts in early adolescence. Approximately 71 to 91% of patients report chronic pain up to 20 years after initial diagnosis.(9) The pathogenesis is complex and multifactorial with multi interactive pathways advocated to contribute to the onset and persistence of pain.(10)
However, the true etiology is still unknown. The factors associated with PFP are lower hip extension strength, lower knee extension strength and lesser flexibility of the lower extremity muscles.(7)
Patient feels crepitus while descending stairs could indicate PFP. Unfortunately there is no patellofemoral special test that has significant accuracy in making diagnosis, so the diagnosis is made primarily on the basis of history taking and subjective assessment. Strong subjective clues such as pain while descending stairs, discomfort with prolong sitting with knee flexed (movie-goer’s sign) helps a physical therapist to make a clinical hypothesis and provocative tests are just considered to be an icing on the cake of assessment.(11) It is non-traumatic in nature, with diffuse anterior knee pain especially on joint loading activities. There is no gold standard method or special test to clinically diagnose PFP. The diagnosis is made on detailed history and objective assessment.(8)
The diagnosis is made if the patient report AKP or peripatellar pain for > 3 months, in the absence of intra-articular pathology. If the patient report pain at least 2 of the following pain provoking functional activities: squatting; stairs climbing; prolonged sitting; running; kneeling and jumping. The pain provoking clinical tests are: tenderness on palpation of patellar facets; positive response on Clarke’s test.(7)
The therapist should ask about recent changes in physical activity, current physical activity and previous history of trauma or knee surgeries. PFP is a common form of knee overuse condition. Joint locking and clicking sensation are not consistently present in PFP, but highlights internal derangements in the knee such as meniscal tears.(1)
Athletes with poor gluteal control are not able to control their hip, which causes the hip to rotate medially. This puts excessive stress through the knee with a valgus stress being exerted and therefore causing compression to the lateral compartment and stress to the medial patellar ligaments. These alignment alterations can result in ITB tightness and eventually can cause a lateral patellar tracking.(12)There is evidence that individuals with PFP demonstrate impairments regarding soft tissue restraints i.e. ligamentous injury especially the medial patellofemoral ligament. Generalized ligamentous laxity is linked with the development of PFP. Such impairments can contribute to patellar maltracking.(13) During weight-bearing, medial rotation of the femur is a contributing factor to lateral patellar tilt.(13) In women with PFP, altered joint kinematics is linked with increased medial rotation of the femur during single leg squat maneuver.(13)
PFJ is considered as the “joint of extensor mechanism of the knee”.(14) Patella has a major role in the distribution of compressive forces by increasing the contact area between patellar tendon and the femur. Patellar articular cartilage is the thickest cartilage of the body, 5-6 mm thick. Patella moves cadually about 7cm as the knee moves from full extension to full flexion. The patella become submerged into the intercondylar groove during full knee flexion.(14) AKP is an explanation of symptoms felt by the patient; however the term is usually misused as a diagnosis. A pseudo-locking effect is reported by patients after first gets up from prolong sitting. It is actually a stiffness, which usually settles after taking a few steps. “Walking downstairs”, aggravate the patient symptoms because the forces acting on PFJ are increased to roughly “three times” the body weight.(14) Individuals with patellar alta (high riding patella) demonstrate diminished contact area for a given knee flexion angle and greater patellofemoral stress while fast walking.(13)
Greater Q-angle or excessive knee valgus causes lateralization of the patella, which increases the loading of the medial patellofemoral ligaments, potentially resulting in PFP. In addition to this, hamstring tightness, leg length discrepancy, muscular imbalances, excessive foot pronation and abnormal trochlea or patella morphologies can bring out PFP.(15) chondromalacia patellae must not be used as a synonym for PFP, although chondromalacia is a condition in which there is pathological changes and softening of articular cartilage. Usually PFP is bilateral and patient report tenderness on patellar facet palpation. The stability of PFJ depends upon both static and dynamic restraints. Pain-free submaximal exercises and prevention of flaring activities having increased patellofemoral joint reactive forces are the fundaments of rehabilitation of PFP. Hip and trunk poor muscular control (hip abductors, hip external rotators, trunk lateral flexors and core weakness) increases the development of increase hip adduction and increase hip medial rotation during standing. This medial femoral torsion further increases the retropatellar stress. There is an increased tendency to have abnormal lower limb biomechanics especially in fatigued athletes who participate in strenuous activities.(16) Individuals with PFP demonstrate calf tightness and navicular drop and this is not a universal finding in all patients.(13)
Different causes of anterior knee pain after ACL reconstruction surgery are: contracture of retropatellar fat pad and patellar tendon and scarring in peripatellar structures and so called “Cyclops lesion”. Pain provocation on coming downstairs is the important finding because the forces acting on the PFJ are approximately three times the body weight. Muscular wasting of oblique fibers of VMO may be present in PFP. Pseudo locking with prolong sitting may be present in PFP.(14) Individuals with PFP demonstrate lesser flexibility in hamstring and quadriceps muscles groups. Tightness of both muscles can increase the PFJRFs.(13) During exercise therapy, importance is forced on the coordinated contraction of the medial and lateral components of quadriceps muscles and also on the coordinated muscular contraction of hip abductors, hip adductors and gluteal muscles.(7)
PFP has been associated with decreased contact area and increased load on the lateral PFJ, as a consequence of patellar maltracking such as increase lateral patellar tilt, translation and spin.(17) Current evidence-based recommended exercise therapy and International consensus, concentrated on knee and hip strengthening, as a cornerstone of management of PFP.(10) The current available evidence advocates that “abnormal loading of the PFJ”, propelled to a larger extent by deficits in quadriceps strength is a hallmark factor contributing to the onset and persistence of PFP.(10)
Patellar maltracking as a consequence of dynamic valgus might be an underlying cause of PFP. Potential reasons of dynamic or functional valgus are decreased hip muscular strength and foot abnormalities (hind foot eversion and pes planovalgus). The clinical importance of such findings is that an individually tailored or customized, multimodal treatment program for each athlete based on their underlying pathology is mandatory.(18)
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