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 22/11/2004. Reviewed Dr ÍOS 01/02/2007, 26/08/2009. Last reviewed Dr ÍOS 16/12/19.