Least common joint to be affected in ankylosing spondylitis is:

Ans: B (Temporomandibular joint) Ref: Harrison's Principles of internal Medicine, 18th edExplanation:"Sacroiliitis is often the earliest manifestations of AS"AS primarily affects the axial skeleton and peripheral jointsCommon sites include the:Sacroiliac jointCostostemal junctionsSpinous processesIliac crestsGreater trochantersIschial tuberositiesTibial tuberclesHeelsArthritis in the hips and shoulders ("root" joints) occurs in 25-35% of patients.Severe isolated hip arthritis or bony chest pain may be the presenting complaint.