Patellofemoral Pain Syndrome (PPS)

Ovid: 5-Minute Sports Medicine Consult, The

Patellofemoral Pain Syndrome (PPS)
Christopher D. Meyering
  • Overuse injury with pain located around or behind the patella
  • Multifactorial in origin resulting in biomechanical changes in normal alignment of the patella
  • Synonym(s):
    • Chondromalacia patella (term frequently used synonymously in older literature; a subset of anterior knee pain related to softening and damage to the articular cartilage)
    • “Runner's knee”
  • Anterior knee pain represents 20–40% of all knee problems.
  • Most common running injury presenting to a sports medicine clinic
Risk Factors
  • Recent increase or change in training/activity
  • Deviations of normal rollover pattern of foot (ie, excessive or insufficient pronation)
  • Patellar hyper- or hypomobility
  • “Miserable malalignment syndrome” (ie, increased femoral anteversion, inward-looking patella, external tibial torsion, pronated feet, and bayonet sign)
  • Valgus deformity of the leg
  • Vastus medialis oblique (VMO) muscle strength deficit relative to vastus lateralis
  • Varus position of the subtalar joint
  • Gluteus medius inhibition or dysfunction; leads to decreased hip control and greater femoral adduction and/or internal rotation
  • Family history of patellofemoral or anterior knee pain
  • Q-angle formerly felt to be a significant risk factor, but multiple studies have not seen any significant correlation when comparing symptomatic and asymptomatic individuals
Commonly Associated Conditions
  • Chondral injury, especially with history of blunt trauma
  • Increased residual laxity or tearing of the medial patellar stabilizers with lateral dislocation of the patella
  • Recent changes in activity frequency, type, and intensity
  • Duration of wearing and changes to current exercise footwear
  • Past effusion, if knee currently not swollen. Effusion is not a typical finding of patellofemoral pain syndrome (PFPS). Its presence is likely related to other pathology, although PFPS cannot be excluded.
  • Subluxation vs dislocation episodes and/or history of direct trauma
  • Prior treatments, including NSAIDs, taping, physical therapy, orthotics, injections, or surgery
  • The presence of crepitus is not helpful to make a diagnosis, as most healthy women and almost half of healthy men also have crepitus on exam.
Physical Exam
  • Insidious onset of anterior knee pain with activity
  • Pain around or behind the patella with one or more of the following activities: prolonged sitting, squatting, stair climbing, running, kneeling, hopping/jumping
  • In-line “giving way” of the knee secondary to pain and not ligamentous or tendinous deficiency
  • Physical examination tests have been reported to have sensitivities <50%, although specificity for some tests have ranged from 72–100% (1)[B].
  • Evaluate gait and overall limb alignment, as mentioned in “Risk Factors.”
  • Note any atrophy of the lower extremity, especially VMO.
  • Assess strength of gluteus medius using Trendelenburg test or side-lying hip abduction test.
  • Examine flexibility of quadriceps (Thomas' test), iliotibial band (Ober's test), hamstring (popliteal angle test), hip (Thomas' test), and gastrosoleus (ankle range of motion).
  • Assess for presence of crepitus or J-sign (abrupt lateral motion of patella with full extension) during active flexion and extension of the knee.
  • Assess for patella alta, patella baja, squinting patella, or grasshopper eyes (proximal and lateral patellar rotation).
  • Rule out patellar and quadriceps tendinopathy, ligamentous instability, and meniscal pathology.
  • Evaluate the prepatellar, infrapatellar, and pes anserine bursae and presence of joint effusion.
  • Examine for patellar facet and retinaculi tenderness. Tenderness over lateral retinaculum present in 90% of patients.
  • Evaluate patellar glide and apprehension:
    • Divide patella into quadrants.
    • If moves 1 quadrant or less laterally or medially, a tight medial or lateral retinaculum is present.
    • If able to translate >3 quadrants medially or laterally, the patella is hypermobile. Hypermobility usually results in apprehension as the patient senses impending patellar dislocation.
  • Perform patellar tilt test: With knee in full or 30 degrees of flexion, if examiner cannot get the lateral border of patella to horizontal with posterior pressure on medial edge, a tight lateral retinaculum is present.
Diagnostic Tests & Interpretation
  • Imaging studies are not required for an accurate diagnosis of patellofemoral pain syndrome. Multiple studies have evaluated sulcus angle, patellar height (determined by Insall-Salvati index), patellar tilt (determined by Laurin angle), and patellar displacement (determined by Merchant angle) and have found no significant difference between symptomatic and asymptomatic patients (1)[A].
  • Imaging studies are recommended if there is clinical suspicion of another diagnosis or if a patient has failed initial conservative management. Most radiographs will appear normal. Any structural abnormalities may need to be addressed when determining the appropriate care plan for an individual patient.
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  • CT, MRI, and bone scintigraphy are recommended to determine presence of additional pathology causing anterior knee pain or to assist with surgical options when conservative management has failed.
  • Plain films:
    • Anteroposterior bilateral standing: May show varus or valgus orientation of femur, knee, or tibia
    • Lateral view of affected knee: Evaluate for patella alta (patella length to patellar tendon length <0.8) or patella baja (patella length to patellar tendon length >1.2) with Insall method.
    • Merchant view of bilateral patellofemoral joints, as this view does not distort the trochlea/patella appearance. Evaluate for a shallow sulcus angle, subluxation degree, and femoral condyle appearance.
    • Tunnel view if osteochondral deficit lesion suspected
  • CT:
    • Useful to evaluate patellofemoral relationships (eg, tilt and subluxation), especially in patients with suspected subluxation at <30–45 degrees of flexion that cannot be visualized well on plain film
    • Useful to evaluate intraosseous lesions
    • Useful to plan selective surgical realignment procedures
  • MRI:
    • Provides information similar to CT
    • May add evaluation of articular cartilage (stage III and IV chondromalacia can be evaluated reliably with accuracy of 89%), presence of loose bodies, and integrity of surrounding soft tissue structures such as the medial and lateral patellar retinacula
  • Bone scintigraphy:
    • Increased uptake at patella and distal femur believed to indicate poor prognosis with prolonged pain (average 6–9 mos)
    • Positive bone scan correlates with chondromalacia, with positive predictive value of 72%.
Differential Diagnosis
  • Patellar or quadriceps tendinopathy
  • Patellofemoral osteoarthritis
  • Patellar instability with subluxation or dislocation
  • Osteochondral defect of the trochlear or patellar surface
  • Osteochondritis dissecans
  • Iliotibial band syndrome
  • Anterior fat pad inflammation
  • Synovial plica
  • Retinacular strain
  • Osgood-Schlatter disease
  • Sinding-Larsen-Johansson disease
  • Referred pain from the hip, often affecting the anterior distal thigh and knee
  • Multiple other sources of knee pain and arthritis (eg, gout, infection, reflex sympathetic dystrophy, neuroma, or sickle cell disease)
  • Pigmented villonodular synovitis
719.46 Pain in joint involving lower leg

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