Sacroiliac joint pain.

The sacroiliac joint is a source of pain in the lower back and buttocks in approximately 15% of the population. Diagnosing sacroiliac joint-mediated pain is difficult because the presenting complaints are similar to those of other causes of back pain. Patients with sacroiliac joint-mediated pain rarely report pain above L5; most localize their pain to the area around the posterior superior iliac spine.

Laboratory evaluation in neck pain.

Laboratory investigations for neck pain play a minor role in most cases. When clinical suspicion of infection or tumor arises, however, laboratory testing can provide definitive information to direct the patient's care. Specialized laboratory testing including autoantibody titers can be useful in confirming and categorizing inflammatory arthritides.