Hello!  When I do sudden movement or too harsh exercise in area of butt and thighs, like squats, or lifting one knee and holding for 40 second, 4 repetitions, and then the other side, the area that gets inflamed is the lower back or right leg side.  Most of the time my hips and lower back are tight.  My goal was to strengthen my core hoping getting it strong would support my back, but lately when exercises get tougher, I hurt my back for one or more days.  I am a lot of time sitting working and probably has taken its toll.