The small lumbar joint is an important joint of the spinal connection, which guides the movement of the spine and resists various forms of load such as compression, shear and rotation.The LFJ, like other joints, can be subjected to degenerative changes and injury when subjected to trauma, abnormal stress and other factors. The joint surface of the LFJ consists of the lateral surface of the inferior articular eminence of the upper lumbar vertebra and the medial surface of the superior articular eminence of the lower lumbar vertebra, and the joint surface has epiphyseal cartilage of about 0.2 mm in thickness, and the two joint surfaces are in a medio-lateral relationship, and the direction of the joint from the first lumbar vertebra to the fifth lumbar vertebra gradually changes from an approximately sagittal position to an oblique position, to an almost coronal position in the fifth lumbar vertebra. The morphology and interrelationship of the articular surfaces of the upper and lower synapses can be divided into four types of LFJ: 1, equal type, in which the upper and lower articular surfaces are parallel to each other in a straight line; 2, embracing type, in which the articular surface of the upper synapse is curved and concave, and the articular surface of the lower synapse is curved and convex as the embrace of the upper synapse; 3, anti embracing type, which is the opposite of the embracing type, in which the lower synapse wraps around the upper synapse; 4, double embracing type, in which the articular surfaces of the upper and lower synapses are each divided into 4.Double-embracing type, in which the articular surfaces of the upper and lower synapses are divided into two parts: concave and convex, with one part encircling the corresponding synapses and the other part being encircled by the corresponding synapses, and the joint space of the synapses is curved in an “S” shape. Among the four types, the first two are more common and the last two are less common. The structure of the joint capsule: LFJ joint capsule is attached to the medial 1~2mm of the edge of the articular eminence in the upper lumbar region, and the more downward, the more inward it is, to the lumbosacral region which is 13mm inward. the joint capsule is thinner on the dorsal side, and the anterior wall is thicker, and its anterior wall is integrated with the ligamentum flavum and participates in forming the posterior wall of the intervertebral canal. the upper and lower walls of the joint capsule are the loosest, which facilitates the joint to slide forward and down or backward. The thickness of the small lumbar joint capsule varies from segment to segment, but there are no significant differences. The joint cavity: Because the two articular surfaces of this joint are of various types, mostly concave and convex, the joint cavity is mostly concave to the medial side and convex to the lateral side in the transverse section with a curved gap, which is narrow, a potential cavity of about 0.5 mm wide, and the entire joint cavity is narrow in the front and wide in the back, increasing from the top to the bottom, with no significant gender differences. When the joint cavity is viewed in the coronal and sagittal planes, cryptic fossae exist in the upper and lower poles due to the loosening of the joint capsule and are filled with synovial folds. The superior articular branch is multi-originated and travels inward and upward through the transverse interosseous muscle to the superior articular eminence, and is distributed in the lateral part of the joint capsule; the middle articular branch is monogenic, i.e., it comes from the posterior medial branch of the lumbar nerve in this segment and is distributed in the lower part of the small joint capsule in this segment; the inferior articular branch is generally monogenic and is distributed The inferior articular branch is generally monogenic and distributed to the upper part of the articular capsule of the inferior segment. Each posterior medial branch of the lumbar nerve is distributed to at least two intervertebral joints in the same plane and the next plane, and each intervertebral joint receives at least two segments of posterior medial branches of the lumbar nerve.