post hip dislocation after effects on muscles

I had a posterior dislocation of my right hip a year and a half ago. I thought that I was pretty much healed. I just recently started conditioning for football, and now I am having problems with the muscles in that leg. I thought that it was a pulled hamstring, but it felt more like a cramp. I could walk with no pain although the muscle does feel weak, but anytime I try to use my hamstring muscle repeatedly it feels like it is going to cramp up again. Does anyone know if this is normal? What could be causing it? What can I do to stop this from happening?