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 adhered due to inflammatory infiltration, and the inflammation can extend widely to the perinephric tissues, causing swollen adhesions or abscess formation in the affected psoas major muscle, which can involve the liver, spleen, colon, inferior vena cava, duodenum, etc., and even form skin fistulas. Diagnosis of swelling of lumbar major muscle: 1. pain: mostly mild dull pain, light at rest, heavy at exertion, aggravated by coughing, sneezing or holding objects, but the patient can sleep better at night, which is different from malignant tumor. Patients complained that the pain site is sometimes inconsistent with the lesion. Patients with lesions in the thoracolumbar segment often complain of pain in the lumbosacral region. If the patient is not examined carefully, or if only lumbosacral X-ray is taken, the diagnosis is often missed. In severe cases of posterior convexity deformity, it can cause lower back strain and produce pain. If the lesion compresses the spinal cord and nerve roots, the pain may be quite intense and radiates along the nerve roots. 2. Postural abnormalities: The posture adopted by patients varies with the location of the lesion. Patients with cervical spine tuberculosis often have oblique neck deformity, with forward sloping head and shortened neck, and always use both hands to hold the jaw. Patients with tuberculosis of the thoracolumbar, lumbar and lumbosacral spine try to tilt their head and trunk back when standing or walking, and prefer to hold the chair with their hands when sitting to reduce the pressure of their weight on the affected vertebrae. Patients with lumbar spine tuberculosis try to pick up things from the ground, bend the knees and hips, avoid bending over, and use their hands to hold the front of the thighs when standing up, which is called a positive pick-up test. 3, spinal deformity: posterior convexity deformity is the most common, mostly angular posterior convexity, scoliosis is not common and not serious. 4, limited spinal activity: due to protective spasm of the muscles around the lesion, the movement of the affected spine is limited, and the cervical and lumbar spine, which have a greater range of motion, are easily detected, while the thoracic spine, which is less mobile, is not easily detected. The normal movement of the spine is in three directions: flexion and extension, lateral bending and rotation. The atlantoaxial joint primarily rotates the head, and if this joint is involved, much of the head rotation function is lost. Younger children who are uncooperative may move the joint passively to observe the restricted motion. Passive movement should not be done with violence to avoid dislocation, paraplegia, or even sudden death. When checking the lumbar spine activity, the child is made to lie prone and the doctor lifts both feet with his hands to lift the pelvis off the bed to observe the posterior extension of the lumbar spine; then the child is made to sit on the bed with his knees extended to observe the forward flexion function of the lumbar spine. 5, pressure pain and percussion pain: because the vertebral body is far from the spinous process, so the local pressure pain is less obvious; percussion of the local spinous process can cause pain. 6.Cold abscess: It is often the earliest sign when patients visit the clinic, and sometimes the abscess is mistaken for a tumor. Sometimes the abscess is deep and not easily detected early, so the abscess should be searched for in the good part of the abscess. 7. Spinal cord compression phenomenon: Some patients come to the clinic because of paraplegia. Even if the patient has no complaints of neurological disorders, the doctor should routinely examine the nerves of both lower limbs in order to detect early spinal cord compression in a timely manner.