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Patellofemoral Pain Syndrome (PFPS)

BASICS

  • Definition: Pain in or around the patella, aggravated by increased patellar loading (sitting, squatting, kneeling, stairs); not attributable to other causes.
  • Synonyms: Anterior knee pain, retropatellar pain syndrome, chondromalacia patellae, runner's knee

EPIDEMIOLOGY

  • Prevalence: Incidence 6% (2007–2011, US); 55% female; 12–15% in military populations
  • Geography: More cases in southern US regions

ETIOLOGY & PATHOPHYSIOLOGY

  • Mechanisms: Increased patellofemoral joint loading, often multifactorial:
  • Patellar malalignment/maltracking (e.g., patella alta, trochlear dysplasia)
  • Quadriceps asymmetry, weakness, or tightness
  • Hamstring tightness
  • Laxity/tightness of lateral retinaculum
  • Increased hip joint internal rotation
  • Altered tibiofemoral mechanics

RISK FACTORS

  • Activity: Running, squatting, climbing stairs, sudden increase in activity
  • Biomechanics: Dynamic valgus, patellar instability, quadriceps weakness, foot abnormalities (pes pronatus, rearfoot eversion)
  • Demographics: Female gender
  • Others: Knee ligament injury/surgery, prolonged synovitis

GENERAL PREVENTION

  • Exercise: Strengthening/stretching—especially hip abductors, quadriceps (terminal extension)
  • Other: Avoid sudden increases in activity

COMMONLY ASSOCIATED CONDITIONS

  • Overuse injury, knee ligament injury, patellar tendinopathy, iliotibial band friction syndrome, prolonged synovitis

DIAGNOSIS

History

  • Diffuse anterior knee pain, exacerbated during/after activity
  • Pain with squatting, stairs, uneven surfaces, running

Physical Exam

  • ROM assessment, check for effusion
  • Pain on palpation of patellar edges
  • Compression/patellar grind test: Pain on patellar compression with quad contraction suggests PFPS
  • Single leg squat: Pain in 80% with PFPS
  • Patellar apprehension test: Pain/apprehension with passive lateral patellar displacement (specific, not sensitive)
  • Patellar tilt test: Assess lateral retinacular tightness
  • Gait/posture: Look for imbalances (femoral IR, hip height, scoliosis, quad atrophy)
  • Footwear: Assess for pes pronatus/rearfoot eversion

Differential Diagnosis

  • Prepatellar bursitis, patellar/quadriceps tendinopathy, chondromalacia, patellofemoral arthrosis, subluxation/dislocation, ligament/meniscal injury, ITB syndrome, plica syndrome, osteochondral defect, Osgood-Schlatter, Sinding-Larsen-Johansson, infection, tumors, referred pain (hip/spine)

Diagnostic Tests

  • Imaging not required unless symptoms are severe, atypical, or persistent
  • Knee x-rays (4 views) if indicated
  • CT for patellar malalignment grading
  • Radiographs may be normal in early stages

TREATMENT

General Measures

  • Conservative: Physical therapy, rehabilitation, NSAIDs (gold standard)
  • Therapy Focus: Strengthening hip abductors, external rotators, knee extensors, core; flexibility (esp. hip, knee)
  • Stretching: Proprioceptive neuromuscular facilitation

Medications

  • Acetaminophen or NSAIDs for pain
  • Glucosamine, chondroitin, hyaluronic acid not routinely recommended

Additional Therapies

  • Patellar taping, manual therapy as adjuncts
  • Foot/ankle orthoses—short-term relief possible, limited evidence for long-term use

Surgery

  • Rarely indicated. Consider only if all conservative measures fail
  • Tight lateral retinaculum: surgical realignment
  • Cartilage defects: resurfacing/restoration

REFERRAL

  • Failure of conservative management
  • Recalcitrant cases with psychosocial overlay—consider mental health referral

ONGOING CARE

  • Patient Education:
  • Home exercise programs, but not a substitute for formal PT
  • Emphasize compliance and participation in specialized therapy
  • Prognosis: May become chronic; >12 months of pain predicts long-term symptoms
  • No clear link to later OA

ICD-10 Codes

  • M25.569 Pain in unspecified knee
  • M25.561 Pain in right knee
  • M25.562 Pain in left knee

CLINICAL PEARLS

  • PFPS = most common cause of anterior knee pain in active adults
  • Clinical diagnosis: accurate history + exam
  • Best evidence: Well-designed exercises for core, hip, and lower extremity strength/flexibility