This randomised trial compared conventional jig-based unicompartmental knee arthroplasty with navigational control against robotic arm-assisted surgery in 107 patients with medial compartment osteoarthritis, all with CT-based planning, the same approach and a standardised rehabilitation programme.
Robotic assistance improved accuracy of both femoral and tibial component positioning, reduced inpatient pain scores and opioid consumption, and shortened hospital stay. But at two years, Oxford Knee Score, KOOS and WOMAC showed no difference. Only the Forgotten Joint Score favoured the robot, at six months and again at two years.
The most revealing detail is not a result at all. Recruitment declined during the trial because eligible patients increasingly asked for the robotic procedure and operating surgeons lost clinical equipoise. That is a candid admission and it matters: a trial that becomes hard to recruit into because everyone already believes the answer is a trial at risk of selecting an unrepresentative final cohort. Set alongside the RACER-Knee result in total knee replacement, where robotic assistance produced no patient-reported benefit at all, the honest reading is that robotic assistance reliably improves what surgeons can measure — component position, early recovery — while its effect on how the knee feels a year or two later remains small and inconsistent.
- Better femoral and tibial component accuracy with robotic assistance
- Less inpatient pain, less opioid use, shorter stay
- No difference in Oxford Knee Score, KOOS or WOMAC at two years
- Recruitment fell as patients and surgeons lost equipoise mid-trial
The statistics, in plain English
When several outcome measures are collected and only one — here the Forgotten Joint Score — separates the groups, the finding needs care. It may be that this score is more sensitive to the difference that exists, or that it is one positive among several by chance. That the three established scores all agreed on no difference is the more weighty signal. Note this is an interim report of a continuing trial, so the two-year figures may yet change.
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