The lumbar intervertebral disc is located between two vertebral bodies and is a structure with hydrodynamic properties, consisting of three parts: (a) nucleus pulposus: the nucleus pulposus is located in the center of the disc and does not touch the vertebral body. The nucleus pulposus is a viscous, transparent gelatinous substance that accounts for about 50% to 60% of the cross-sectional surface of the intervertebral disc. The nucleus pulposus contains a collagen fiber meshwork, a mucopolysaccharide protein complex, and chondroitin sulfate, which gives the nucleus pulposus the ability to bind water. The water content of the nucleus pulposus accounts for about 75-90% of the total nucleus pulposus. The nucleus pulposus allows for uniform pressure on the spine when under pressure, and changes in disc height in normal people are related to changes in water in the nucleus pulposus. As age increases, the water in the nucleus pulposus is gradually lost and the morphology of the nucleus pulposus changes. The nucleus pulposus is plastic and becomes flattened under pressure, allowing pressure to be transmitted in all directions. In the activity of adjacent vertebrae, the nucleus pulposus acts as a fulcrum, like a ball, moving forward or backward with the flexion and extension of the spine. In addition, the nucleus pulposus acts as a fluid exchange between the vertebral body and the cartilage end plate, and the fluid in its contents can diffuse to the vertebral body by osmotic pressure, and the nutrition of the nucleus pulposus depends on the permeation of the cartilage end plate, which is closely connected with the spongy bone, and the spongy bone of the vertebral body has a rich blood supply with no interstitial bone separating the cartilage end plate, and the change of pressure can make the fluid exchange in the vertebral body. (ii) Fibrous ring: The fibrous ring is located around the intervertebral disc and is divided into three layers: outer, middle and inner. The outer layer is composed of collagenous fibrous bands and the inner layer is composed of fibrocartilaginous bands. Between the layers there are bonding-like substances to make each other firmly bonded together. The anterior and bilateral parts of the fibrous ring are the thickest, almost twice as thick as the posterior part, and the posterior part is the thinnest, but there are usually 1-2 layers of fibers, which are arranged diagonally and closely in layers to surround the nucleus pulposus and form the peripheral part of the intervertebral disc, like a coiled spring, which connects the upper and lower vertebrae to each other and keeps the liquid component of the nucleus pulposus, maintaining the position and shape of the nucleus pulposus. The fibrous ring is very strong and is tightly attached to the cartilaginous endplate to maintain the stability of the spine. (iii) Cartilage endplates: The cartilage endplates are located on the upper and lower sides of the intervertebral disc and are composed of fibrocartilage, one on each side of the vertebral body. The cartilage plate, like articular cartilage, can withstand pressure to prevent the vertebrae from being overloaded and protect the vertebral body. The cartilage plate is a transparent, non-vascular cartilage tissue with an average thickness of 1 mm. there is no nerve tissue within the cartilage plate, so when the cartilage plate is damaged, it neither produces painful symptoms nor can it repair itself. The cartilage endplate protects the vertebrae, cushions pressure, connects the vertebral body to the intervertebral disc, and acts as a nutrient exchange for the disc.