Ankylosing spondylitis (AS), a common type of spondyloarthropathy, is a chronic inflammatory disease that affects spinal joints, and adjacent soft tissues such as sacroiliac joints, tendons, and entheses (1). Inflammation of the spinal structures and progressive changes in the surrounding tissue is largely responsible for decreased physical function and mobility in participants with AS (2).~It is unknown how these parameters of AS participants with AMSI (smaller than 5 cm) are affected compared to AS participants with normal modified Schober index (NMSI, bigger than 5 cm). In addition, it is unclear which demographic characteristics and variables predispose AMSI to occur.~This study will aim to compare AS participants with abnormal modified Schober index (AMSI) versus AS participants with normal modified Schober index (NMSI) in pain, morning stiffness, balance, kinesiophobia and the fear of falling. In addition, the investigators will aim to determine which demographic characteristics and variables predispose AMSI to occur
This study will aim to compare ankylosing spondylitis (AS) participants with abnormal modified Schober index (AMSI) versus AS participants with normal modified Schober index (NMSI) in pain, morning stiffness, balance, kinesiophobia and the fear of falling. In addition, the investigators will aim to determine which demographic characteristics and variables predispose AMSI to occur