When you attend your doctor he will take a history and then examine your back (looking for muscle spasm, noting the posture and mobility) and then look at all the other parts of the body, searching for evidence of ankylosing spondylitis.
Before the disease showing normal joints between the Sacrum and Upper Pelvis and between each vertebra. Hip joints can also be affected but this is less common and movement can be restored by surgery (Arghroplasty).
The disease in its early stages showing changes in the Sacrum and Upper Pelvis. Evidence can also be seen of changes beginning to take place in the joints between vertebra.
The disease in advanced stage, the Sacroiliac joints are fused and the joints between the vertebra have been joined together by boney changes (Ossification). This produces the effect sometimes known as 'Bamboo Spine`.