arthroplasty
Painful Total Knee Arthroplasty
advanced
6 min
20 marks
6 questions
Clinical Scenario
A 65-year-old man presents with persistent anterior knee pain 18 months after primary TKA for osteoarthritis. He describes diffuse pain, worse with stairs and kneeling. He had been progressing well until 6 months ago when symptoms began. The knee has "never felt right." On examination, he walks with a limp. Range of motion is 5-95 degrees. Ligaments are stable. There is tenderness over the medial joint line and pes anserinus area.
AP, lateral, and skyline radiographs of TKA showing well-positioned components with neutral alignment. No obvious loosening, radiolucent lines, or malalignment. Joint line appears appropriate. Patella tracks centrally on skyline.
Source: AI-Generated: Normal TKA Radiographic Series (AP/Lat/Skyline) • OrthoVellum AI • OrthoVellum Educational Use
Questions
Question 1 (4 marks)
What is your differential diagnosis for painful TKA?
Question 2 (4 marks)
What investigations would you perform? Include specific thresholds.
Question 3 (3 marks)
CRP is 12 mg/L. Aspiration shows WCC 1500/μL with 45% PMN, cultures negative. How do you interpret these results?
Question 4 (4 marks)
CT shows 8° internal rotation of the femoral component. What is the significance and management options?
Question 5 (3 marks)
What technical factors during primary TKA help prevent anterior knee pain?
Question 6 (2 marks)
What are the outcomes of revision TKA for unexplained pain?
Exam Day Cheat Sheet
Must Mention
- •EXCLUDE INFECTION FIRST (aspiration, CRP, alpha-defensin)
- •CT rotation protocol: femoral IR >3° = significant
- •Combined rotation (femoral + tibial) >10° = problematic
- •Revision for unexplained pain = 40-50% satisfaction ONLY
- •Always examine hip and spine for referred pain
- •Cannot fix rotation with poly exchange - need component revision
Common Pitfalls
- •Revising without clear mechanical cause
- •Missing component malrotation on plain films
- •Not examining hip/spine
- •Poly exchange for rotational malposition (won't work)
- •Not considering pes anserinus/soft tissue causes