Of or relating to or near the small of the back and the back part of the pelvis between the hips. The lumbosacral junction consist of the L5 vertebral body articulating with the first sacral vertebral body. In the seated position the lumbosacral discs are loaded three times more than standing.
The L5-S1 disc is deep in the pelvis, and does not have much motion. It is also connected to the sacrum by a large ligament (sacral-ala ligament) which helps limit motion.