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arthroplasty

Stiff Total Knee Arthroplasty

advanced
6 min
15 marks
5 questions
Clinical Scenario
A 62-year-old woman presents 10 weeks after primary TKA for osteoarthritis. She reports persistent stiffness with ROM 5-75° despite intensive physiotherapy. Pre-operative ROM was 0-115°. She has difficulty with stairs and rising from chairs. The knee is not particularly painful at rest. There is no warmth, erythema, or wound concerns.
Lateral radiograph of TKA showing adequate component positioning. Assess for joint line elevation, femoral component sizing, tibial slope, and overstuffing.
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Lateral radiograph of TKA showing adequate component positioning. Assess for joint line elevation, femoral component sizing, tibial slope, and overstuffing.

Image source: Open Access medical literature (NIH/PubMed Central) • CC-BY License

Questions

Question 1 (3 marks)

What are the causes of stiffness after TKA? Classify your answer.

Question 2 (3 marks)

What investigations would you perform and what are you looking for?

Question 3 (4 marks)

Describe your management algorithm based on timing and findings.

Question 4 (3 marks)

Describe your technique for manipulation under anaesthesia and post-MUA protocol.

Question 5 (2 marks)

What factors predict poor outcome after MUA?

Exam Day Cheat Sheet

Must Mention

  • •Pre-op ROM is the strongest predictor of post-op ROM
  • •MUA optimal at 6-12 weeks, declining benefit after 12 weeks
  • •ALWAYS exclude infection in ANY stiff TKA
  • •Technical causes (malposition, overstuffing) require REVISION not MUA
  • •CT rotation protocol: internal rotation >3° = revision indication
  • •Joint line elevation >8mm contributes to stiffness

Common Pitfalls

  • •Not excluding infection before MUA
  • •Performing MUA when technical problem present (revision needed)
  • •Delaying MUA beyond 12 weeks (poor outcomes)
  • •Excessive force during MUA (fracture risk in osteoporotic bone)
  • •Inadequate post-MUA physiotherapy

Exam Tips

  • →Stiff TKA: flexion <90° or flexion contracture >15°
  • →MUA window: 6-12 weeks optimal
  • →MUA success rate: 80-90% if early
  • →Femoral malrotation threshold: 3° internal
  • →Joint line elevation threshold: 8mm
  • →MUA gain: average 20-40° additional flexion
  • →Fracture risk with MUA: 1-2%