What Is a Partial Knee Replacement?
A partial knee replacement (unicompartmental knee arthroplasty, or UKA) resurfaces only the arthritic compartment of the knee, most commonly the medial (inner) compartment, less frequently the lateral (outer) or patellofemoral (kneecap) compartment. The remaining healthy cartilage and ligaments are preserved.
Advantages Over Total Knee Replacement
- Smaller incision and less tissue disruption
- Shorter hospital stay (typically 1–2 days)
- Faster recovery — most patients reach full function by 2–3 months
- More natural-feeling knee — the ACL and PCL are retained
- Less blood loss and lower infection risk
Who Is Suitable?
Partial knee replacement is appropriate for patients with arthritis confined to one compartment, an intact ACL, no significant knee deformity or inflammatory arthritis, and a body weight within reasonable range. Careful patient selection is critical to achieving good outcomes. Approximately 20–25% of knee replacement candidates are suitable for partial replacement.
Limitations
The main limitation of UKA is a higher long-term revision rate compared to TKR, particularly due to disease progression in the other compartments over time. At 10 years, approximately 10–15% of UKAs require revision to TKR. However, revision from UKA to TKA is generally straightforward.
Recovery
Patients mobilise with a physiotherapist on the day of or day after surgery. Hospital stay is 1–2 days. Crutches are used for 2–4 weeks, followed by a walking stick. Return to driving is typically 4–6 weeks. Most patients are walking freely and returning to leisure activities by 2–3 months.