Partial Knee Replacement: Why Keeping Part of Your Knee Is the Better Choice

Understanding Knee Compartments

The knee has three compartments:

• Medial (inner side) — the most commonly worn, accounting for ~70% of UKA cases
• Lateral (outer side) — less common; important to consider in valgus (knock-knee) deformity
• Patellofemoral (kneecap–groove) — isolated kneecap arthritis; covered separately

In a total knee replacement (TKA), all three surfaces are resurfaced, and the ACL is sacrificed. In a partial (UKA), only the affected compartment is replaced, and — critically — the ACL is preserved.

An intact ACL is the reason UKA feels more natural. The ACL provides proprioceptive feedback and coordinates knee motion. Patients who have had a UKA routinely describe their knee as feeling "more like their own knee" than friends or family who have had a total replacement.

Who Is a Candidate for Partial Knee Replacement?

Selection is the single most important factor in UKA outcomes. Classic Oxford criteria (widely adopted since the 1990s) specify:

• Anteromedial (medial compartment) osteoarthritis on weight-bearing X-rays
• Functionally intact ACL on clinical exam
• Flexion contracture ≤ 15° and flexion range ≥ 90°
• Varus (bowlegged) deformity ≤ 15° that corrects to neutral passively
• No significant patellofemoral arthritis causing anterior knee pain
• No inflammatory arthritis (rheumatoid, etc.)

At my practice in Miami, I evaluate candidates with weight-bearing X-rays, clinical exam, and — when anatomy is borderline — MRI to assess cartilage in all three compartments. The single biggest mistake in UKA is offering it to a patient who actually has tricompartmental disease. Proper selection eliminates this error.

Research from the Oxford group has shown UKA survival rates of 91% at 10 years and 82% at 15 years when performed in appropriately selected patients — comparable to TKA, with superior functional outcomes (Bone Joint J 2019;101-B(8):1011).

Advantages Over Total Knee Replacement

For the right candidate:

• Faster recovery: Most UKA patients walk without a walker by 2–3 weeks; most TKA patients need 4–6 weeks.
• Less blood loss and shorter surgery: UKA typically takes 45–60 minutes; TKA takes 75–90 minutes.
• More natural feel: ACL preservation means proprioceptive feedback is maintained.
• Easier revision if needed: If UKA ever fails (polyethylene wear, progression of arthritis), conversion to TKA is technically straightforward — you haven't "burned any bridges."
• Usually outpatient: Most of my Miami UKA patients go home the same day.

The Recovery Timeline

Day of surgery: Walk with a walker or cane. Manage stairs before discharge.

Week 1–2: Walking with a cane; most daily activities possible. Swelling is the limiting factor, not pain.

Week 3–4: Many patients are cane-free by day 14–21. Driving typically at 3–4 weeks for left knee/automatic or 4–6 weeks for right knee.

Month 2–3: Return to golf, light hiking, cycling. Patients are generally at 80–90% of final function by 6 weeks.

Physical therapy for UKA is less intensive than TKA — typically 4–6 weeks of outpatient PT rather than 8–12 weeks.

Common Concerns

"What if my arthritis spreads to the other compartments?" — This is the main reason some surgeons prefer TKA. However, progression of arthritis in preserved compartments is relatively slow, and UKA survival data at 15–20 years is reassuring for correctly selected patients.

"Is a smaller implant less durable?" — Modern UKA implants, particularly the fixed-bearing Oxford design, have excellent long-term data. The revision rate at my practice mirrors the published literature.

Frequently Asked Questions

Q: How long do partial knee replacements last? A: Published survival data shows 82–91% at 10–15 years in appropriately selected patients. This is comparable to TKA survival rates.

Q: Can I return to sports after partial knee replacement? A: Yes. If you already golf, play tennis, ski, run, cycle, or swim, the goal is to send you back to that sport without the arthritis pain. This practice does not put lifetime restrictions on activity you were already doing.

Q: Is partial knee replacement covered by insurance? A: Yes. UKA is a covered procedure under Medicare and most private insurance plans through UHealth.

Q: What if I need a total knee replacement later? A: Conversion of UKA to TKA is a well-described procedure with outcomes comparable to primary TKA. The "bridge-burning" concern is not supported by the current literature.

Educational information only. Individual candidacy, outcomes, and recovery timelines vary and require medical evaluation.