A 28 year-old man developed low back pain radiating down the right leg. Examination showed an absent right ankle reflex, weakness of right knee flexion and ankle plantar flexion, and patchy loss of sensation over the right lateral foot and posterior lateral leg. Straight leg raise on the right caused severe pain radiating down from the buttock to the ankle; similar testing on the left was not associated with any symptoms.

Among spinal disorders, herniated disks are very common. Disks are located between the vertebral bodies. They are composed of a thick annulus fibrosis surrounding a jelly like interior known as the nucleus pulposus. The anterior and posterior longitudinal ligaments run along the front and back of the vertebral bones and disks respectively. Disk herniations most often occur posterior laterally, where they compress the exiting nerve root at that level. Straight posterior disk herniations, although less common, may result in direct spinal cord or cauda equina compression.