The lumbar spine refers to the lower back, where the spine curves inward toward the abdomen. It starts about five or six inches below the shoulder blades, and connects with the thoracic spine at the top and extends downward to the sacral spine. “Lumbar” is derived from the Latin word “lumbus,” meaning lion, and the lumbar spine earns its name. It is built for both power and flexibility – lifting, twisting and bending. See Spinal Anatomy and Back Pain The lumbar spine has several distinguishing characteristics: The lower the vertebra is in the spinal column, the more weight it must bear. The five vertebrae of the lumbar spine (L1-L5) are the biggest unfused vertebrae in the spinal column, enabling them to support the weight of the entire torso. The lumbar spine’s lowest two spinal segments, L4- L5 and L5-S1, which include the vertebrae and discs, bear the most weight and are therefore the most prone to degradation and injury. The lumbar spine meets the sacrum at the lumbosacral joint (L5-S1). This joint allows for considerable rotation, so that the pelvis and hips may swing when walking and running.
Lumbar Spine Anatomy and Pain