arthritis of the spine caused by infection with Brucella, the organism of undulant fever. Arthritis generally occurs several weeks after the initial infection and may involve any part of the spine, but the lumbar region is the most commonly affected site. Symptoms include severe low back pain, recurrent fever, headache, and muscle and joint pain. The disease destroys both intervertebral disks and adjacent vertebrae but can be arrested with antibiotics and immobilization of the joints.