There are many reasons for the hidden pain inside the left lumbar side, the first consideration is chronic muscle strain. Usually, prolonged high-intensity labor, sports or frequent bending and poor sitting posture can cause excessive fatigue of the muscles and tendons of the left lumbar region, resulting in discomfort such as soreness, swelling and hidden pain. In addition, it may also be caused by trauma, inflammation, lumbar spine diseases, urinary system diseases, etc. 1. Trauma: If the patient’s left side of the lumbar region is crushed, impacted, stepped on, forcefully twisted and other trauma, it may cause acute soft tissue injury, usually the initial pain is more intense, and then can gradually manifest as hidden pain, and in severe cases, it can be accompanied by lumbar activity limitation, swelling, etc. 2. Inflammatory diseases: lumbar myofibrositis, transverse synovitis, rheumatoid arthritis, etc., mainly due to cold and cold, bacterial infection, external pulling, etc., in addition to vague pain, patients can also be accompanied by redness and fever in the affected area of the left lumbar region; 3, lumbar spine diseases: lumbar sacralization, lumbar spinal stenosis, lumbar spine tumor or tuberculosis, etc., can cause compression of the spinal cord or nerve roots of the left lumbar region, resulting in vague pain, numbness, mobility disorders, muscle weakness, etc., in the lateral side of the left lumbar region. 4.Urological system diseases: If the patient has hidden pain in the left side of the lumbar region and is accompanied by hematuria and difficulty in urination, it is considered that it may be caused by urological system diseases, including left kidney stone, ureteral stone, pyelonephritis, etc. 5.Intestinal tumors: including benign and malignant tumors of the intestinal tract, which may cause involvement pain, manifesting as left lumbar region and abdomen with The discomfort of vague pain, accompanied by weight loss, anemia, intestinal obstruction, etc.; 6. gynecological diseases: if female patients, they should also consider the vague pain on the left side of the waist caused by gynecological diseases such as endometritis and pelvic inflammatory disease, as well as a series of clinical manifestations such as lower abdominal pain, fever and increased leucorrhea.