Robotic-Assisted Partial (Unicompartmental) Knee Replacement

Overview

Robotic-assisted partial knee replacement, or unicompartmental knee arthroplasty (UKA), resurfaces only the damaged compartment, preserving the rest of the joint's bone and ligaments. Candidates return to sport more often than after total knee replacement (80.7% vs 69.0%) and report higher satisfaction (90.1% vs 81.3%), but registry data also show a real, higher revision rate (Vossen et al. 2025; Jansen et al. 2020).

How Dr. Raffo Performs This Procedure

Robotic-assisted partial knee replacement begins with either preoperative imaging or intraoperative registration that builds a three-dimensional map of the diseased compartment. The robotic arm guides bone preparation within a pre-planned envelope and allows the surgeon to check and fine-tune ligament balance and component position before the implant is finally seated. Only the damaged compartment is resurfaced; the cruciate ligaments, the healthy cartilage in the other compartments, and the native bone stock elsewhere in the joint are left alone (OrthoInfo/AAOS). Robotic guidance measurably improves the precision of component placement: in a Level I randomized trial, 80% of tibial components landed within 2 degrees of the sagittal-plane target with robotic assistance, compared with 22% using conventional instrumentation, with similar gains across femoral positioning parameters (Bell et al. 2016). Even with the robot, roughly half to four-fifths of components land within that 2-degree window depending on which plane is measured — the technology narrows the spread of outliers, it doesn't eliminate them. Robotic assistance adds operative time, on the order of 15.6 minutes on average across pooled data (Bensa et al. 2024).

Who Is This For?

Partial knee replacement is for patients whose arthritis is genuinely confined to one compartment of the knee — most often the medial side — with the rest of the joint's cartilage and ligaments intact. The traditional Kozinn and Scott selection criteria (age over 60, weight under 180 lb, minimal deformity, no heavy labor) have been substantially relaxed by modern evidence: a 1,000-knee series found 68% of patients would have been considered "contraindicated" by those classic rules, yet had no difference in 15-year implant survival and, in several measures, better function than the "ideal" group (Hamilton et al. 2017). What has not been relaxed are two things: inflammatory arthritis and significant ligament instability remain contraindications, and disease that has spread beyond one compartment — particularly meaningful patellofemoral bone loss — still points to a total knee replacement instead (OrthoInfo/AAOS; PMC6026888). An ACL-deficient knee is not an automatic exclusion, but it is a specialist-level decision rather than a routine one — one well-matched series found equivalent 5-year survival with or without an intact ACL, while other reviews report failure rates as high as 16% in ACL-deficient knees without reconstruction (Kikuchi et al. 2021; Joints review).

Recovery & Rehabilitation

Recovery from partial knee replacement is generally faster than from a total knee replacement, largely because less bone and soft tissue are disturbed during surgery.

• Day 0–1: Most patients are stood up and walking within 24 hours, and many go home the same day or within 24 hours of surgery (Oxford NDORMS patient booklet). A systematic review of nearly 9,700 patients found successful same-day discharge in 88% overall, rising to 91% in carefully selected patients (Bayoumi et al. 2022).
• 0–2 weeks: Walking aids are recommended for about two weeks; patients are advised not to discard crutches too early (Oxford NDORMS patient booklet).
• 6 weeks: Most patients are walking without aids and can drive once off crutches and in full control of the vehicle; leisure activities and gym work can typically begin in this window (Oxford NDORMS patient booklet).
• 3 months: Strenuous activity should still be avoided up to this point, and this is generally when return-to-work timing is finalized depending on job demands (Oxford NDORMS patient booklet).
• 6–12 months: High-impact activity and sport are typically cleared in this window, with 80.7% of partial knee patients returning to some level of sport, compared with 69.0% after total knee replacement, and full recovery continuing to progress up to a year (Vossen et al. 2025; Oxford NDORMS patient booklet).