I would get with a good trainer (not your average 24 hour fitness trainer) or PT person and rebuilt that leg. Otherwise you're going to be at high risk of blowing out you knee or any number of injuries caused by lost coordination and strength in that leg. As Jordan suggested, I'd try to get into squat patterns provided that the glutes are firing properly, and you have no imbalances that are causing things like femur rotation, adduction, or abduction, while you squat. You might start by isolating glutes, quads, hams, and then moving to integrated movements after a couple of weeks (like squats) once all is working well.
I would also start on some kind of reactive or plyo training to get your body used to impact again.