The pain in the lower side of the left waist against the hip refers to the pain in the left hip, which may be caused by soft tissue injury, lumbar intervertebral disc herniation, hip arthritis and so on. 1. Soft tissue injury: strenuous exercise or too much exercise can cause the left hip muscles, ligaments, fascia and other prolonged tension, easy to form soft tissue congestion and edema, resulting in swelling and pain. 2. Herniated lumbar intervertebral disc: because of degenerative changes in the spine, the nucleus pulposus of the intervertebral disc protrudes, causing irritation or compression of the nerve roots around the spinal cord, resulting in pain in the left side of the hip, lumbar region, and even pain in the outer side of the left leg. 3. Hip arthritis: mostly related to obesity, over activity, metabolic abnormality or congenital dysplasia, trauma, infection and other factors, mainly manifested as pain, stiffness, swelling and limited activity of the hip joint. Left lower back against the hip pain may also have other reasons, it is recommended to go to the hospital in a timely manner, improve the examination to clarify the cause of the disease, give targeted treatment or treatment.