Can I have full range of motion in my knee 4 years after surgery?

I had a benign cyst in my knee under the patella that was surgically removed in 2006. It has been hurting to this day, I think because of weak muscles around the knee. I hadn't really been doing knee strengthening exercises. I did physical therapy after the surgery and then again in 2008. I had some muscle strength back after that. Then in 2009 I ran track in school and last year I ran track also, but I got little muscle strength gain. I am trying to regain muscle in my knee and quads and trying to regain full range of motion in my knee. Is it possible? and if so, how long until it I get full range? Also my kneecap is kind of stiff and when i bend my knee and I have pain. What can I do?