Ankylosing spondylitis  An inflammatory disorder that affects the low back and pelvis and produces stiffness and pain

Anulus fibrosus The outer ring of fibrous material surrounding the nucleus pulposus of the intervertebral disks

Cauda equina The terminal nerve roots of the spinal cord located within the vertebral canal; so named because they resemble the tail of a horse

Neurogenic claudication Leg pain that occurs as a result of compression of nerves within the spinal canal; often associated with spinal stenosis

Nucleus pulposus The central core of gelatinous material within intervertebral disks

Osteophytes Overgrowth of bone, common in osteoarthritis and spinal stenosis

Saddle anesthesia Decreased sensation around the perineum

Spinal stenosis Narrowing of the canal housing the spinal cord; commonly caused by encroachment of bone

Spondylolysis A defect or fracture of the pars interarticularis, the portion of bone located between the superior and inferior articular processes of the vertebrae

Spondylolisthesis Anterior displacement of a vertebral body relative to the adjacent vertebral body below

Vascular claudication Leg pain that is caused by ischemia secondary to vascular disease; the pain uniformly occurs with activity and is relieved with rest