Hi, I had a total knee replacement 1 year ago. Had a great recovery. 2 months ago My quad kept giving out. Some times I couldn't stand. Crazy were good, exam good until suddenly I couldn't raise my leg of walk. Went back to Physical therapy. Got better. Last week I couldn't turn my leg inwards toward other leg. Couldn't put socks on couldn't get up unless leg, knee and foot was aligned. Even hanging my leg and swinging it left or right 1 inch causes me to yell. What can this be? I am a nurse who works 12 he shifts in the Nicu. I go to the gym and pool 3 days/week