Robotic knee surgery matches standard care in 339-patient trial

In 10 UK hospitals, surgeons used a robotic arm to help place artificial knees in 339 patients. One year later, the patients could not feel a difference: pain, walking ability and recovery were similar to those after conventional surgery. The finding comes from RACER-Knee, a large randomized, participant- and assessor-masked clinical trial published in The Lancet.

The robot did do one thing better. It positioned surgical instruments with greater precision, allowing surgeons to adjust cutting angles and depths to a patient’s anatomy. That could support more personalized knee replacements than the standard approach, in which surgeons rely on their experience and a conventional set of instruments. But greater technical accuracy did not improve the trial’s main measure, the Forgotten Joint Score, which records how much patients notice their artificial joint during daily activities.

The trade-off was tangible. Robot-assisted total knee replacements took an average of 10.5 minutes longer and cost around £950 more on average. Under current NHS cost limits, the system tested was not cost-effective over the first year. It was also not linked to a higher risk of serious adverse events, suggesting safety comparable to conventional surgery.

So what changes for patients now? Not much in the first year: the trial does not show less pain, better movement or faster recovery from robotic assistance. For hospitals, it offers a precise tool but adds time and cost without a demonstrated short-term patient benefit. The researchers will continue following participants for 10 years, including to assess whether the approaches differ in the need for further knee surgery.

That longer view is where the technology’s promise remains. Professor Andrew Metcalfe of the University of Warwick said more work is needed before robotic assistance produces benefits such as less pain or better movement. Professor Edward Davis of Birmingham’s Royal Orthopedic Hospital said surgeons still need a better understanding of the ideal implant position and how to personalize it for each patient before the robot’s precision can be fully used.