Ankylosing spondylitis: integrated clinical and physiological perspectives.

This hypothesis paper draws upon clinical epidemiological and physiological perspectives of axial muscle tone relevant to ankylosing spondylitis (AS). Skeletal muscle tonus is the property of intrinsic tension or resistance to stretch with no additional muscle contraction. The interpretations call attention to novel concepts of the intrinsic axial muscular system contributions to enthesopathic lesions in AS. The axial kinematic chain extends from the entire spine to the posterior aspects of the lower extremities and is essential for postural and mobility functions. Muscles and articular cartilage derive from common embryological precursor cells and are complexly coordinated in the maintenance of postures and dynamic functions. A definitive link between axial muscular dysfunction and respective joint pathology has not yet been demonstrated in AS. However, the following clinical epidemiological and physiological observations raise the possibility of a relationship between axial muscular hypertonicity and AS, which will be reviewed sequentially.