By all accounts, total knee replacement is a game changer. So why subject it to a randomised, controlled trial? First, total knee replacement poses risks. About 0.5 to 1% of patients die during the 90-day postoperative period. The risks of deep venous thrombosis, pulmonary embolus, deep prosthetic infection, and periprosthetic fracture range from 0.1 to 1.0%, with higher risks among older persons and those with a higher number of coexisting conditions.