So yesterday was leg day.. I decided to do something different, and that was DB squats before my lunges.. I still can't do regular squats until my knee is capable of supporting the weight. While I was doing the DB squats, my lower back would start aching (while coming up out of squat). I was following form correctly (straight back, forward head, chest high, flat feet, bending at knees and hips)... Could this be from just weak core? Wasn't severe pain or anything, just an annoying ache..