The L5-S1 disk, located between the L5 and S1 vertebrae, supports the L5-S1 vertebral segment, according to Spine-Health. Spinal disks provide shock absorption, stability and slight mobility to the spine.
The L5-S1 vertebral segment is also known as the lumbosacral joint, states Spine-Health. The L5-S1 vertebral segment makes up the base of the spine and consists of many interconnected parts. The L5-S1 disk is made up of two parts, a protective outer portion and gelatinous inner core. Herniation or degeneration of the L5-S1 disk can cause pain in the lower back and legs by exerting pressure or by exposing inflammatory proteins from the core to the L5 nerve root.