just about ripped my right patella off when i caught it between a trotting 1300 lb horse and a tree trunk at about 12mph. was never so close to passing out from pain before or since. it swelled up to the size of a grapefruit, mostly water, and then receded to orange/lemon size for about five months. never did have it immobilized and never had to work to get full range of motion. it just slowly came back, plus a little superficial nerve damage, with normal use.