Creating the perfect total knee replacement requires a very delicate balance between bone, implant, muscles, and ligaments. The surgeon may be working with osteoporotic bone or a joint with a natural extra rotation in one direction or another.
Once the arthritic or damaged bone is removed to make room for the implant, the surgeon must choose the right size and type of prosthesis for each patient. Replacing the anterior or front portion of the femoral bone (thighbone) with an implant that is larger than the bone removed is called overstuffing. Too much overstuffing can cause pain and loss of motion (flexion).