The patella rests inside a groove on top of the femur called the trochlear groove. If you bend and straighten your knee, the patella moves back and forth inside this groove. X-rays. X-rays offer pictures of dense structures, for example bone. Your doctor will get X-rays from various various angles in order http://knee cap replacement https://www.theorthopaedicandpainpractice.com/knee-cap-replacement-understanding-the-basics-of-this-orthopaedic-surgery/