'The young man woke up in the morning with a stiff back and feeling tired – indeed after moving about for some time, his back hurt less, just as his physician had said.' This is the typical picture of an ankylosing spondylitis patient – whose spine is gradually getting 'rigid'.

Ankylosing spondylitis affects as many as one to two out of every 1000 males globally; prevalence being much lesser in women. It is a rheumatic disease that causes chronic inflammation of joints (arthritis). The most commonly affected joints affected are those of the spine and the joints between the spine and the pelvis (sacro-iliac joints). The condition ultimately leads to rigidity ('ankylosis') of the affected joints on account of abnormal adhesion of the bones in the joint.