OBJECTIVE Ankylosing Spondylitis (AS) is an inflammatory rheumatism characterized by its disease course with flares leading to progressive ankylosis of the spine related to paravertebral ligamentous and discal structures ossification. AS patients suffer significantly more vertebral fractures than control groups. These fractures could affect cervical spine. They are due to either ankylosis-related flawed spine compliance or AS-induced osteoporosis. BACKGROUND The physiopathology of this osteoporosis is multi-factorial, but essentially linked to AS-related inflammatory phenomenons. It is marked by reduced bone density (at lumbar spine and femoral neck), increased bone turnover (with increased urinary C-telopeptide cross-linked collagen type 1), but without any significant change in phosphocalcic blood parameters. Histological features are depressed bone formation, with either maintained or increased resorption. CONCLUSIONS The screening of this osteoporosis is based upon investigating people at risk (progressive inflammatory AS) using dual-energy x-ray absorptiometry and biochemical markers of bone turnover. Treatment is based upon a modulation of both inflammatory phenomenons and bone remodelling using bisphosphonates and anti-TNF alpha.