<prompt> Which joint is rarely affected by ankylosing spondylitis -AnkleHipShoulderSacroiliac  <response>: Ans. is a i.e., Ankle Joints involved in ankylosing spondylitis Ankylosing spondylitis primarily affects axial skeleton. The disease usually begins in the sacro-iliac joints and usually extends upwards to involve the lumbar, thoracic, and often cervical spine. In the worst cases the hips or shoulders are also affected. Hip joint is the most commonly affected peripheral joint. Rarely knee and ankle are also involved 