Methods for differentiating sacroiliitis from ankylosing spondylitis

Early manifestations of ankylosing spondylitis include sacroiliac joint pain. Over time, patients develop significant lower back pain and morning stiffness in the muscles. The condition primarily affects the sacroiliac joints, and magnetic resonance imaging (MRI) can provide a definitive diagnosis. For ankylosing spondylitis, spinal X-rays along with laboratory testing for HLA-B27 are usually performed, but diagnosis is generally not easily established by combining clinical symptoms alone.