On my last long ride on 6/7 (60 miles, 4100 ft. elevation gain) I developed a slight pain in one of the... ligaments(?) on the back side of my knee. I've been looking at knee anatomy charts all day and can't figure out what it is. It's circled in red in the pic (not my legs): knee pain.jpg
It wasn't debilitating and I would barely even call it a pain, but I could feel that something was off. If it makes any difference, I did a 5k off-road run the Thursday before that but felt fine after the run. I'm not much of a runner but try to do a 5k once a week.
On Tuesday last week, I realized that I had overreached a little and took Wednesday through Friday off. Aside from a slow 1 hour walk on Wednesday, I didn't do anything remotely strenuous. On Saturday I went for a very slow (like sub-10 mph average) 8 mile recovery ride, felt fine afterward, and figured that everything was good. On Sunday I rode 30 mph. Lots of short rolling hills between 3-5%, nothing too strenuous but I did set my fastest average speed for the year. After the ride, I started to feel the slight pain behind my knee again.
Any ideas on what it is and what I should do about it? I had a professional bike fitting (Specialized BG fit) done a few years ago and until now haven't really experienced any pain since then. Right now it isn't even bad enough to really keep me from riding, but I don't want it to turn into something worse. There's not really any way to avoid hills around here, but would I be fine if I take it easy, avoid anything too steep, and RICE it at night? I've lost 28 lbs. since January and only had 2 more to go to not be overweight anymore, so I'd REALLY like to keep riding somehow!