Hi Trishy, yes, AS can make you feel like your pelvis is locked up, soon after I started having SI joint problems I noticed that I had lost my range of motion in the the whole hip/pelvic/lower back area, it was like watching someone with no rythym dance, nothing moved independantly anymore and is still that way...but I have lumbar spine fusion too...I hope your son finds an answer and welcome to KA!
