 I am Dr. Hemant Kalyan, consultant and head of the Department of Orthopaedics and Sports Medicine working at Manipal Hospital, Bangalore. This is a question that a lot of people ask, Doctor, what exactly is a knee replacement surgery? Now, in a knee replacement surgery, we hope to accomplish three things. First of all, we said that the joint surface has become rough and irregular. So we replace it with a perfectly smooth joint. So if you just look at this model over here, you have this part of the knee which is artificial, this part which is artificial and the white plastic which is in between. So the surface is replaced by this material, top and bottom. This part goes on the surface of the high bone. This component goes on the surface of the knee bone, the leg bone and in between the two we have a high density plastic. So you also have on the inner side of the kneecap a plastic component. So as we see here, there is a combination of a metal with plastic or high density polyethylene which replaces the surface of the knee and forms the new knee. So all the ligaments of the body are preserved. The muscles are the patient's own, naturally the bones are the patient's own but the surface of the joint which was originally rough and irregular is made perfectly smooth and regular. The second thing we do in a knee replacement is to correct the alignment of the leg. We mentioned that in osteoarthritis the person's leg often becomes bow leg or not knee. This is corrected at the time of surgery by balancing the ligaments in such a way that the person gets a nice straight alignment of the leg after the surgery. The way this helps is that when a person stands and walks the body weight is evenly distributed across the knee and doesn't fall more on one side or the other side. The third thing we do in the knee replacement is to recreate the gap of the knee. So as I mentioned in osteoarthritis the gap becomes narrower because the cartilage is lost and the bones become closer to each other. When we put a metallic component on the two ends and a plastic component in between then this will recreate the gap in the knee joint. So these are the components of the knee joint. This is known as the femoral component which lies on the thigh bone. Over here you have something known as a tibial base plate which goes inside the leg bone and in between the two you have the white here which is the plastic component and together they form the new total knee replacement. So this is of course a very skilled surgery and we have a lot of tools including aid with computers, navigation and of course the surgeon's own judgement and eyesight which is the most key factor in giving a well-aligned, well-balanced knee which should serve the patient well.