Lumbar spinal stenosis is a series of low back pain and a series of neurological symptoms caused by various forms of narrowing of the spinal canal, neural canal, and intervertebral foramen, as well as soft tissue-induced changes in the volume of the spinal canal and narrowing of the dural sac itself. This is called lumbar spinal stenosis. Because of the narrowing of the spinal canal, the cauda equina nerve in the spinal canal is compressed, resulting in symptoms such as low back pain and leg pain. If the spinal canal is narrowed laterally, the nerve roots will also be compressed, causing interruption of the axial pulp due to compression; impaired nerve fluid function; relative swelling of the nerve sheath; stimulation of nerve endings; and tissue hypoxia due to obstruction of blood flow; restricted venous return and local stagnation, etc. These constitute the causes of low back pain. Lumbar spinal stenosis refers to the abnormal structure of the spinal canal caused by primary or secondary factors, narrowing of the spinal canal cavity, and the emergence of intermittent claudication as the main feature of the back and legs. Various forms of narrowing of the spinal canal, neural canal, and intervertebral foramen, as well as soft tissue-induced changes in the volume of the spinal canal and narrowing of the dural sac itself cause a series of low back pain and a series of neurological symptoms to appear. This is called lumbar spinal stenosis. In some clinical cases, lumbar disc herniation is diagnosed before surgery, but there is no herniated disc or only a small protrusion during surgery, and the main lesion is lateral stenosis of the spinal canal compressing the nerve roots, which is called lateral saphenous stenosis to distinguish it from main spinal stenosis. Lateral saphenous fossa refers to the narrowing of the spinal canal extending laterally, mainly in the trilobar spinal canal, most typically in the lower two lumbar vertebrae. The lateral saphenous fossa is generally considered to be narrow if the anterior and posterior diameters are less than 3 mm, normal if they are more than 5 mm, and relatively narrow if they are in between. So, why is the lateral saphenous fossa narrowed? Congenital factors can cause lateral saphenous stenosis. The deep lateral saphenous fossa and small anterior-posterior diameter of the trilobar spinal canal are developmentally predisposed to stenosis. Another important factor contributing to stenosis is fading. Degeneration of the intervertebral disc with calcification of the fibrous annulus, hyperplasia of the posterior superior edge of the vertebral body, which protrudes from the anterior to the posterior into the lateral saphenous fossa; supra-articular synapse of the inferior vertebra after disc stenosis; hyperplasia of the isthmus, hypertrophy and calcification of the ligamentum flavum, which protrudes from the posterior into the lateral saphenous fossa; and anterior or posterior slippage of the degenerated vertebral body can all contribute to lateral saphenous fossa stenosis.