Patellofemoral arthritis takes place when the articular cartilage along the trochlear groove and over the underside of the patella wears down and will become inflamed. A plastic button, or go over, is used to resurface the bottom with the patella. This button will line up with a thin steel component https://knee-cap-replacement76319.blogacep.com/39459878/knee-cap-replacement-no-further-a-mystery