Left lower back pain in young people may be caused by sprains, urinary stones, lumbar disc herniation, female gynecological diseases such as uterine prolapse, pelvic inflammatory disease, ovarian cyst torsion. 1. Sprain: The lumbar region is a vulnerable part of daily activities, when the patient carries out strenuous activities of the lumbar region, working for a long time, lifting heavy objects and other actions, it may cause acute sprain and contusion of the left lumbar muscles, and the left side of the lumbar pain, limited activities and other symptoms. 2. Urinary stones: mainly including ureteral stones, urinary tract stones, etc., if the occurrence of the site in the left side, to the left side of the waist as the main symptom of obvious colic, and in the acute phase of pain intolerable, very intense. 3. Lumbar disc herniation: generally aggravated after bending and working, due to the degeneration of the lumbar vertebrae aging, compression to the nerve root, causing lumbago, lower limb pain, numbness of the knee. Most patients have a history of repeated episodes of lumbar pain, accompanied by radiating pain in the lower limbs. 4. Female gynecological diseases: mainly including uterine prolapse, pelvic inflammatory disease, ovarian cyst torsion, etc., all of which can cause left lumbar pain. There are many causes of left lower back pain in young people, it is recommended to consult a doctor in a timely manner, under the guidance of the doctor to clarify the cause of the disease, timely targeted treatment, so as to avoid delaying the condition.