I am a 35 yr old female. I had a back fusion at l4-s1 about 4 yrs ago. I have recently been having a lot of pain when I bend forward and try to straighten back up. It feels like it locks on me. So I had an xray done, and it shows that I have anterlothesis of l4 on l5, and it increases with flexion. My pain doctor referred me to a surgeon because he said it should not be moving like that due to it being fused there. Is he right? Is this abnormal movement?