As promised, here is a picture of my insides.
The glossy white area at the top is the femur. The bottom is the Tibia. That chunk of swirl in the middle is what does not belong there. It is a huge piece of meniscus that tore free a little at a time, painfully over several years and have pretty much just been in the way ever since. The surgeon expertly removed it without damaging the cartilage above or below it.