Hospitals paid a premium for knee-surgery robots. A new UK trial says patients didn't benefit.

A carefully masked UK trial asked whether the Mako surgical robot, marketed as a precision upgrade for total knee replacement, would let patients forget their new joint faster than standard instruments. It did not.

Between December 2021 and December 2023, the RACER-Knee study randomly assigned 339 patients across 10 British hospitals and 33 surgeons to either Mako-assisted or conventional knee replacement. Both patients and assessors were masked; surgeons used sham incisions and redacted operative notes so the postoperative team could not tell which arm a patient was in. The primary outcome was the Forgotten Joint Score, a patient questionnaire asking whether people stop noticing their replaced knee in daily life. The prespecified bar for success was a 12-point gap.

At 12 months, patients in both arms scored essentially the same: 49.2 in the Mako group versus 50.2 in the conventional group, an adjusted mean difference of -1.5 (95% CI -7.5 to 4.5; p=0.62). The small observed difference favored conventional surgery. Serious adverse events were identical: 16 in each arm.

The authors' interpretation, published in The Lancet: in routine-practice delivery, robotic-arm-assisted knee replacement was more costly and did not provide a clinically meaningful patient benefit at one year. Long-term follow-up is ongoing, so durability and revision data are not yet in.