Post Knee Surgery Complications help?

I got a knee injury in 2008 that caused my patella to slip out of place weekly and frequently in my sleep, in June of last year I got surgery to correct it which worked except now my knee locks, and gives, I have trouble walking on slopes or uneven terrain. I still have numbness in my knee, as well as burning, and muscle spasms. I now have to walk with a cane to avoid falling and ease the pain from walking. Also I cant bend my knee much further than 100 degrees. Has anyone heard of anything like this, I see and Orthopedist and he helps a lot but its been almost a year and I want to get back to my life, I'm in my early 20s in college. Any related information would help.