So many big words, right? When is your doctors appointment. Subchondral marrow edema means you have fluid building up or a lesion in your bone marrow and it is usually from a fracture or osteoarthritis. Osteochondral lesion also often comes about due to fracture. Sublexation of petella I believe means dislocation of the knee cap. Mucinous degenerative change is kind of rare from what I've read and can limit motion. Are you experiencing that? Plica are layers in the knee. There are usually 4 and they help it bend and move. It sounds like there is an issue with your medial plica. It can be from irritation or injury.
Sounds like your knee is jacked up. When is your appointment with your doctor to go over the findings? Can you come back and tell me what he says?