Left iliac pain may be caused by physiological factors such as long-term compression and strenuous exercise, or it may be caused by diseases such as femoral head necrosis and osteoarthritis. 1. Physiological factors: the left iliac bone may be compressed for a long time due to the incorrect posture at work, study and sleep, which may lead to the symptoms of left iliac bone pain. In addition, the symptoms of left iliac pain may be caused by a lot of strenuous exercise. 2. Necrosis of femoral head: Necrosis of femoral head may be caused by release of embolism, damage of blood vessels in the bone and high pressure in the bone, etc., and the patients will have the symptoms of bilateral hip pain, groin pain, hip and knee pain, etc. 3. Osteoarthritis: the etiology of osteoarthritis is not clear, and it is considered to be caused by age, obesity and other factors. The main symptoms of patients are joint pain, joint stiffness, joint enlargement and so on. When the symptom of left iliac pain occurs, it may be caused by physiological factors, and at this time, treatment is generally not required. If the symptoms persist or aggravate, you should consult a doctor in time to identify the cause of the disease and follow the doctor’s instructions for treatment.