The knee is a complex joint kind of like a spur gear some rolling and some sliding. Worked for almost 3 years at a lower limb prosthetics component company. Have designed ankle and knee joints and we had a few looks at joints that replicated the real knee. The problem is that prosthetics don't always need to replicate human joints they just need to work. How close to a real knee do you need to be? I believe that if your looking for a model for development you could probably build one yourself using a 4 bar linkage designed to approximate the motion of the lower leg bone covered with a layer of flexable polyurethane foam and skined with about .040 to .060 silicone. or you could purchase a prosthetic knee joint and get a prosthetist to build the rest for you. Check out Seattle Orthopedic Group maybe give them a call.
I got the ok yesterday for total knee replacement on both knees. I was wondering if anyone had heard of a breakthrough in artifical knee construction materials. It seems that the knees used today have a life of 12 - 15 years. I thought I had heard of something new in the pipeline but can't remember where I saw it.