i'm in the same boat as you. i tore my ACL and MCL and had surgery (patellar) to replace the ACL on april 25th. anyway, i just recently started to gain my full flexion back. i had my extension pretty early in the game, and maintained it, it was just the flexsion that was giving me trouble. i would hover around 95-110 degrees and go no further. just recently i've broken the 120 mark and i'm on my way back to normal. like the penultimate poster said, ride the bike. that's what helped me the most.
i was going to make a post about this in the grappling forum. i don't know when i'll return to the mat, but i know i'm not ready yet; i don't feel i have the strength in the knee. if someone tried to break my guard, i'm scared that the knee will buckle or something. maybe i'm just gun shy, but i know my body pretty well and i don't think it's ready yet.
after i go for my 6-month check-up on the knee, then i'll see what's up. but for the time being, i'm just working on my knee's flexibility and steady building my leg strength back.
good luck, and i wish you a speedy recovery.