Knee pain - Patellofemoral



Summary

Dx and Mx a challenge. Overuse and muscular dysfunction common contributors. Initial management includes quads strengthening. Check footwear and add arch supports if necessary.

Background

Retropatellar / peripatellar pain from changes in patellofemoral joint.

Also referred to as anterior knee pain, runner’s knee, and chondromalacia patellae.

All ages but max younger adults and teenagers (growth spurt).


Causes

  • Overuse/overload, biomechanical and muscular dysfunction. Theories in bold below

Pes Planus (Pronation) - "Flat feet"

  • Combination of eversion, dorsiflexion and abduction of foot leads to compensatory internal rotation of tibia and femur, stressing patellofemoral fxn
  • Treat with medial foot arch support and footwear advice

Pes Cavus (High arched foot, supination)

  • Less cushioning for leg when foot strikes ground causes more stress on patellofemoral mechanism especially when running
  • Advise proper (cushioned) footwear with arch support

Muscular causes

  • Quads weakness causes instability.  Treat with MVO exercises

Key Clinical Features

  • Gradual onset anterior knee pain (±bilateral) with exercise - particiularly squatting, hiking, running. Often worse going down hill
  • Rarely after patellar dislocation or direct trauma
  • ±patellar crepitus
  • Pain free at rest but can also occur with prolonged sitting (movie-goer's sign)
  • Clinical Dx with Hx and patellar pain on squatting (80%) and patellar margin tenderness (70%)

Red Flags

Investigations

Consider plain x-rays only if concern about Osteochondritis dessicans or rare neoplasm (red flags or lock / letting down)

Differential diagnoses

  • Hip pathology in children / adolescents
  • Lower patellar tender - Sinding Larson or Osgood Schlatter?
  • Effusion = another (cartilage/meniescal/ligamentous) pathology
  • Popping patellar subluxation?
  • Check for other joint symptoms (arthropathy)

Management

  • Quadriceps (especially VMO) exercises.
    • Physiotherapy supervised hip, hamstring and calf iliotibial band stretching exercises (NNT 3.6)
  • Relative rest - initially, e.g. change to swimming in runners
  • Patient education (NNT 5 at 24 months)
  • Movie-goers should start walking regularly
  • Ice - particularly immediately after running (for 10 - 20 minutes)
  • No strong evidence for (or against) NSAIDs
  • Do not use knee splint / braces (unless physiotherapist requests)
  • Taping the knee - no strong evidence either way - physiotherapist can educate patient how to tape their knee for trial
  • Quality footwear - Arch support usually helps (NNT 4)
  • Surgery only for true chondromalacia (fraying retropatellar cartilage)
  • Spontaneous resolution. Masterful inactivity (by physician) may be best option in growing adolescents

Prognosis

Most patients do well with conservative management.


Content by Dr Íomhar O' Sullivan. Last reviewed Dr ÍOS 18/10/21.