New safety concerns over knee replacements The long-term safety and effectiveness of millions of knee replacement implants is unknown, highlighting inherent problems in the regulation and monitoring of medical devices, according to a leading surgeon. Andrew Carr, professor of orthopaedic surgery at the University of Oxford, warned that surgeons are being hindered by a lack of reliable information as the demand for knee implants grows. There are more than 15 companies producing dozens of slightly different knee implants that UK surgeons can pick from depending on patient characteristics and surgical preference. Unlike medicines, companies are not required to clinically test medical devices in patients - they must only prove that a knee, hip or breast implant is safe and durable outside the body in order to gain the required kitemark. Writing in The Lancet, Professor Carr points out that an aging population and increase in obesity rates means the dramatic rise in knee implants looks set to continue. "Widespread surveillance of existing implants is urgently needed alongside the carefully monitored introduction of new implant designs as part of well-conducted large-scale randomised trials," he wrote. There were 76,780 knee replacements in 2010, a 30 per cent increase in five years, according to the National Joint Registry, which monitors the failure rate of implants by analysing data submitted from surgeons. However, the information on the registry is organised into groups of similar components per brand, making it difficult to monitor individual products.