Those half bosu balls upside down for squats (standing on flat side).
One legged squats on the round side. Even just standing on one leg on the round side for as long as you can.
I hear squats with smaller weight, higher reps is good.
I buggered up my ligaments on the insides of my knees playing indoor soccer. Physio had me work on them pretty hard and I think they came back better. Not much blood flow around that part so you've gotta work hard on flexibility/range of movement of the joint if it's been damaged.
I'll throw in the standard disclaimer - SEE A PHYSIO and don't listen to me