Dear Patient, since you are having ankylosing spondylitis it is very likely that ist is both bone and muskle. Since your soine is probably not straight, this can cause muskles to tense up and cause the symptomes desribed. What can help you is back exercise like physical therapy, swimming, yoga, pilates or similar. However, if this doesn t get better you should see a gp or orthopedic doctor to look at your back and eventually have some x-rays of the spine done. Hope this is helping you , if you have any clarificatons you can get back to me, if this was helpful please kindly rate my answer. Best regards