when my leg goes past a 45 degree angle and i move it back it makes a loud click and then it starts to grate. not very painful but getting worse. i have had a lamonectomy L4 L5 S1 and also have suspected ankylosing spondulitis. my doctor just thinks i am moaning. i have asked for a scan and gone through physio but it seems because i can still walk i am fine... no scan

Summarized question: What causes ankylosing spondulitis?