I tore my **ACL** training for a MMA tournament. Had total ACL reconstruction using a cadaver and arthroscopic surgery to scrape calcium deposits off my knee cap( doc said 9 months before I could do any cutting movements etc)  
I did intense rehab and stretching for three months, gradually went to the **leg press** high foot placement and increasingly heavy loads.  
I then began **box jumping** on a low box about 20 inches many times smaller for lateral jumps.  
I jumped rope and did lots and lots and lots of **lunges**.  
I also **quit** leg extensions as the put unnatural tension on your ACL and patella tendon.  

By April 2011 ( August surgery) I was jogging up two 2 and 1.5 miles a day. I continued **basic pt movements** , **leg press** and **lunges** then in January of this year I did my first **deadlift** in over 2 yrs.  
I also began weighted **back squats**. My knee feels better than ever, I tweaked it yesterday landing odd on a high box while doing seated box jumps, but I'm fine just had some fluid on it the next day.  
So my rehab was basically insane amounts of pt movements always using resistance bands, Jump rope, squats using body weight, jogging and lunges brought me back from the dead. Now I am squatting  500 and deadlifting 520. I only box squat now because its safer and strengthens the posterior chain and upper quads/ hip fleckers which is way more important than lower quad development. I do **sled pulls** the strengthen quads and lunges/ reverse lunges. **Step ups** with moderate weight also helps tremendously.  

The only reason I still bust my ass is because I am finishing my masters in Sports Science and opening my own athletic training facility/ power lifting club since their are none in my town. I admit my squat was once 800 lbs and my dead was once  about 750. I don't care if I can ever lift that again, but in order to train others I need to at least perfect my lifts. I put 20 lbs back on my deads and squats after switching to the conjugate system march of this year. I plan to be back to 800 dl and sq but if I don't make it its no big deal.