Looks like a torn miniscus, requiring orthoscopic surgery. The MRI was intensely boring, 30 minutes in an alarmingly loud tube listening to the faint strains of country in a set of pilot earphones. Also, I had to work hard not to flinch or move a muscle in my leg. I’ll find out on Monday if I succeeded.
Here is one section of this $1000+ procedure. What was surprising to me is that they still use black and white film (like XRAYs) for MRIs. Seems depressing low-tech, given I know they can do cool 3D color fly-throughs. I cannot believe that 20 films of my knee is easier for a doctor to look at than some manipulable 3D color image on his computer screen with zoom & pan controls. But hey, what do I know.