Patellofemoral arthritis happens once the articular cartilage along the trochlear groove and on the underside of the patella wears down and will become inflamed. Throughout this process the orthopedic surgeon eliminates the ruined cartilage and a small volume of bone within the joint area with the patella and replaces it http://knee cap replacement https://www.theorthopaedicandpainpractice.com/knee-cap-replacement-understanding-the-basics-of-this-orthopaedic-surgery/