Psoas major muscle, also known as the large psoas muscle, is a long pike shaped muscle that originates from both sides of the lumbar vertebrae and is mostly caused by inflammation. It can be seen in yellow granulomatous pyelonephritis, where the perinephric fascia is thickened and adherent due to inflammatory infiltration, and the inflammation can extend widely to the perinephric tissues, causing swelling and adhesions or abscess formation in the affected psoas major muscle, which can involve the liver, spleen, colon, inferior vena cava, duodenum, and even form skin fistulas. The following diseases are also causes of swelling of the lumbar muscle: 1. chronic strain injury of the lumbar muscle is actually chronic injury inflammation of the lumbar muscle and its attachment point fascia, or even periosteum, and is a common cause of lumbago. The strain is mostly chronic, and there is no clear history of acute trauma; some patients have a history of heavy physical labor, strenuous exercise or trauma; some patients have poor posture or have worked bent over for a long time. The symptoms are sometimes mild and sometimes severe, usually improving after rest and worsening after exertion, and cannot sit and stand for long periods of time and must change position frequently. Some patients have different degrees of pressure pain at the interspinous, posterior superior iliac spine, sacroiliac joint or lumbosacral joint, and the second and third transverse processes of the lumbar spine, and some patients have a wide range of pressure pain or no fixed pressure pain point. 2, lumbar disc herniation Lumbar disc herniation can be divided into: bulging, protrusion and prolapse. Lumbar disc herniation is the diagnosis of Western medicine, but Chinese medicine does not have this disease name. Instead, the disease is grouped under the category of “lumbago” and “lumbar leg pain”. This disease is one of the more common lumbar disorders in clinical practice, and is a common and frequent disease in orthopedics and traumatology. It is mainly due to the degenerative changes of various parts of the lumbar disc (nucleus pulposus, annulus fibrosus and cartilage plate), especially the nucleus pulposus, which, under the action of external factors, rupture the annulus fibrosus of the disc and cause the nucleus pulposus to protrude (or prolapse) in the posterior part or the spinal canal, resulting in stimulation or compression of the adjacent tissues, such as the spinal nerve roots and spinal cord, resulting in lumbar pain, numbness and pain in one or both lower limbs. Numbness, pain and a series of other clinical symptoms.