I was in a car wreck last january and my knee hit the dash board. An MRI showed some bleeding in the posterior knee. But it all seems to have been healed, but my knee hurt me considerably up until I started to do body weight squats. It hurt to do anything once I bent my knee 20 or 30 degrees, and it often got very swollen. I started doing body weight squats - am know doing 400 one or two days a week. I start off doing half squats and by 100 or so can go until my glutes touch my calves.
Not too long ago I could do 315 squat for 15 reps. i have not been able to squat with weight this year. I think I will be able to again. The body weight squat has helped rehab my knee immensely. Much more than the 2 orthopedic surgeons I went to.