Time is relative. For patients undergoing a knee replacement – it will be as if no time has passed, as they will be asleep. For family members in the waiting room, it can be a couple of hours before they have a chance to see their loved ones, depending on the anesthesia used. For me, it usually takes between 30 minutes to an hour to perform a knee replacement depending on patient anatomy. This is because I perform all parts of the operation, including exposure, implantation, and closure.