Complete knee replacement is a very common joint replacement surgery and the number of patients having the surgery is on the rise. However, up to a quarter of patients continue to experience problems with pain or imbalance after the surgery.The Attune knee replacement system claims to allow patients to function better after surgery by decreasing these problems. The aim of this study is to compare the Attune system with existing methods, to see if the new system gives pateints better function and less complications.