Overview of Knee Pain
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Knee pain accounts for about 1 in 50 general practice presentations – and is thus a very common presentation.

Presenting features

  • Swelling that occurs within 30 minutes of an injury is typically haemarthosis
    • This is more commonly associated with ACL injuries
  • Swelling that occurs over a period of days is typically synovial fluids / effusion
  • Any red, warm swollen joint is septic arthritis until proven otherwise

Ligamentus injuries

  • Collateral ligament tears require prompt surgical treatment
  • Other ligament injuries – such as ACL and PCL, as well as meniscal injuries are not so time-critical
  • Twisting injuries tend to cause meniscal injuries
  • Lateral force injuries tend to cause cruciate ligament and collateral ligament injuries

Differentials

  • Patellofemoral syndrome
    • The most common cause of knee pain
    • Typically an overuse injury
    • A bit of a “catch-all” term for minor ligament and muscle strains – which are usually benign and self-limiting
    • Previously known as “chonromalacia patellae”
  •  Injury
    • ACL
    • PCL
    • Collateral ligaments
    • Meniscal tear
    • Tibial plateau fracture
    • Patella fracture
    • Patella dislocation
  • Infection
    • Septic arthritis
  • Rheumatological disorder
  • Referred hip pain
  • Referred neuropathic pain (L3 – S1)
  • Osteoarthritis
  • DVT
    • and ruptured Baker’s cyst
  • Cancer (primary or metastatic)
  • Paediatrics

Knee pain red flags

  • Fever
  • Acute swelling (with or without trauma)
  • Unexplained chronic pain

Investigation

  • Ottowa knee rules – for indication for x-ray – if ANY of the following are present, x-ray is indicated:
    • Unable to weight bear
      • Cannot take 4 or more steps
    • Aged >55
    • Tenderness at head of fibula
    • Inability to flex to 90 degrees
  • MRI
    • May be indicated if any evidence of ligaments or meniscal injury
    • Typically as an outpatient procedure (unlikely to be indicated in Emergency Department)
  • Knee aspiration
    • Indicated in any red, warm, swollen knee
    • To assess for septic arthritis (and gout)

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Dr Tom Leach

Dr Tom Leach MBChB DCH EMCert(ACEM) currently works as a GP Registrar and an Emergency Department CMO in Australia. He is also a Clinical Associate Lecturer at the Australian National University. After graduating from his medical degree at the University of Manchester in 2011, Tom completed his Foundation Training at Bolton Royal Hospital, before moving to Australia in 2013. He started almostadoctor whilst a third year medical student in 2009. Read full bio

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