Knee Replacement: TKR vs UKA, Indications & Post-Op Rehab

Knee Replacement (Arthroplasty)

Knee arthroplasty is the definitive treatment for end-stage arthritis. It involves resurfacing the damaged bone ends with metal and plastic components.

1. Types of Replacement

• Total Knee Replacement (TKR): Resurfacing of Medial, Lateral, and often Patellofemoral compartments. Best for Tricompartmental OA or Inflammatory Arthritis (RA).
• Unicompartmental Knee Replacement (UKA/Partial): Resurfacing ONLY the medial (usually) or lateral compartment. Ligaments must be intact.

2. Indications & Contraindications for UKA

Ideal Candidate for UKA:
- Isolated medial compartment OA.
- Intact ACL and MCL.
- Range of motion > 90°.
- Minimal deformity (< 10° varus/valgus, < 5° flexion contracture).
Contraindications: Rheumatoid Arthritis (affects whole joint), ACL deficiency, Obesity (Relative), Stiff knee.

3. Rehabilitation Principles

• Day 0-1: Mobilization with walker. Quadriceps activation.
• Weeks 1-6: ROM goals (0-90°), Gait training.
• Complications to Watch: DVT, Infection, Peroneal Nerve Palsy (Foot drop), Stiffness.

25 Practice MCQs

Q1. UKA is preferred over TKR for:

Answer: A). Faster recovery and feels more "natural" because ACL is kept.

Q2. Rheumatoid Arthritis is a contraindication for UKA because:

Answer: A). Disease will progress to other compartments. TKR is needed.

Q3. The most important ligament that MUST be intact for UKA is:

Answer: A). ACL deficiency leads to instability and failure of UKA.

Q4. A fixed flexion deformity of > 15 degrees is:

Answer: A). TKR allows extensive soft tissue release to correct deformity.

Q5. "Resurfacing" in TKR means:

Answer: A). Most ligaments are often sacrificed (ACL).

Q6. Patellar resurfacing (replacing patella button) is:

Answer: A). Done if anterior knee pain is a major symptom.

Q7. Peroneal Nerve Palsy (Foot Drop) after TKR is often due to:

Answer: A). Nerve runs lateral; correcting valgus stretches the lateral side.

Q8. The "Polyethylene" insert acts as the:

Answer: A). Located between the metal femoral and tibial components.

Q9. Weight bearing after cemented TKR is:

Answer: A). Cement provides instant fixation.

Q10. Infection after TKR often requires:

Answer: A). Biofilm on implant prevents antibiotics from working.

Q11. Range of Motion (ROM) goal after TKR is typically:

Answer: A). Enough for stairs and sitting.

Q12. Pre-operative quadriceps strength is:

Answer: A). "Prehab" is important.

Q13. Which is an advantage of UKA over TKR?

Answer: A). But has higher revision rate (due to progression of OA in other compartments).

Q14. Aseptic Loosening is:

Answer: A). Most common reason for revision long-term.

Q15. "Clunk Syndrome" is caused by:

Answer: A). Scar tissue problem.

Q16. What is the "Golden Standard" for DVT prophylaxis?

Answer: A). Combined mechanical and chemical.

Q17. Manipulation Under Anesthesia (MUA) is used for:

Answer: A). Breaks adhesions.

Q18. Posterior Stabilized (PS) TKR sacrifices the:

Answer: A). Uses a cam-and-post mechanism to substitute for PCL.

Q19. Cruciate Retaining (CR) TKR preserves:

Answer: A). Requires a healthy PCL. ACL is almost always removed in TKR.

Q20. Metal allergy is a concern with which material?

Answer: A). Hypoallergenic implants (Oxinium/Titanium) used if allergic.

Q21. Knee effusion for > 6 months post-op suggests:

Answer: A). Abnormal.

Q22. Robotic-assisted TKR aims to:

Answer: A). Accuracy < 1mm/1 degree.

Q23. Cryotherapy (Ice) is used in rehab to:

Answer: A). Standard post-op care.

Q24. Extensor mechanism disruption (Patellar tendon rupture) during TKR is:

Answer: A). Results in loss of active extension.

Q25. BMI > 40 (Morbid Obesity) is associated with:

Answer: A). Many surgeons require weight loss first.