The possible causes of left hip pain include sacroiliitis, hip synovitis, femoral head necrosis, lumbar disc herniation and so on. 1. Sacroiliac arthritis: Sacroiliac arthritis may be related to age, heredity and physical fitness and other factors, caused by unilateral or bilateral sacroiliac joint inflammatory reaction, the patient’s main symptoms manifested in the lower lumbar or hip pain. Pain in the left hip may be caused by sacroiliac arthritis. 2. Hip synovitis: Hip synovitis refers to the inflammation of the synovium in the hip joint due to trauma, bacterial or viral infection, joint disorders, metabolic reactions and other stimuli, which is mainly manifested as hip pain, swelling, limited activities and other symptoms. 3. Necrosis of the femoral head: Necrosis of the femoral head may be caused by ischemia of the femoral head resulting in structural changes of the femoral head, collapse, etc. Typical symptoms are pain in the groin area, which can be radiated to the buttocks on the same side, and the pain is often intermittent and progressively aggravated. 4. Lumbar disc herniation: it may be caused by the degeneration of lumbar disc, long-term head down and stooping activities and other bad lifestyle reasons, resulting in lumbar disc herniation, the main symptoms of lumbar pain and sciatica, and the pain is radioactive, can be radiated to the buttocks, causing the phenomenon of the left buttock pain. Left hip pain may also have other causes, it is recommended to go to the regular hospital in time to improve the relevant examination, clear the cause of the disease, under the guidance of the doctor for targeted treatment or treatment.