Ankylosing Spondylitis (AS) is a chronic painful progressive inflammatory arthritis of unknown etiology primarily affecting the spine and sacroiliac joints. In addition to formation of new bone leading to syndesmophytes and ankylosis; osteoporosis is also a prominent feature in AS-thus showing the paradox of new bone formation at abnormal sites coexisting with reduced bone mass & increased fracture risk. Osteoporosis is a common complication of AS, with an incidence between 18.7% and 62%. TNF alpha has a central role in disturbing this balance in bone metabolism--resulting in accelerated alveolar bone loss and decreased strength- i.e. osteoporosis. The investigators hypothesis that anti TNF therapy is effective in active AS resistant to conventional therapy and helps in improving the bone density and over all bone health.