I've had my right knee replaced and don't even think about using your left foot. You'll be using the right knee as soon as you want to use your machine again. Just be SURE to do the therapy - that part is miserable but worth EVERY LITTLE PAIN - and as soon as you finish - you'll be 100% and won't even be able to feel that new knee and will wonder if they really did replace it! It works just GREAT! Good luck......