The patella rests in the groove on top of the femur known as the trochlear groove. After you bend and straighten your knee, the patella moves backwards and forwards inside this groove. Usually about six months or so prior to the Procedure, there will be described as a 'pre-admission' or 'pre-evaluation' clinic. http://knee cap replacement https://www.theorthopaedicandpainpractice.com/knee-cap-replacement-understanding-the-basics-of-this-orthopaedic-surgery/