The s1 lumbar spine is generally referred to as the L5-s1 intervertebral disc, and the lumbar vertebrae L4 and L5 are positioned at the most inferior part of the lumbar spine. There are five lumbar vertebrae in total, L4 and L5 are at the position where the lumbar vertebrae are the most downward and intersect with the sacral vertebrae. And L5-S1 is the intervertebral disc between the fifth lumbar vertebra and the first sacral vertebra, located in the lower lumbar section, which is one of the intervertebral discs with more lumbar vertebrae activity and pressure, and it is prone to intervertebral disc degeneration and disc herniation. This can be found by counting the thoracic vertebrae, which involves locating the lowermost rib on either side of the back of the lower back, which is the 12th rib. Following the 12th rib, the 12th thoracic vertebra can be felt in the direction of the spine, and the 12th thoracic vertebra can be felt downward on the posterior midline to gradually feel the spinous processes of L1 to L5. If there is any discomfort in the position of L4 and L5 lumbar vertebrae, you should consult a doctor in time to clarify the cause and then give targeted treatment.