Sudden leg pain can be seen in the following reasons: First, thigh muscle pain, the reason can be considered as whether too much exercise, in this case pay attention to rest on, but also massage to relax. Second, necrosis of the femoral head or lumbar spine compression nerve, synovitis and other pathological factors, to diagnose clearly, corresponding to each cause to treat. For patients with severe femoral head necrosis, consider replacing the femoral head if necessary. Such diseases lie in early detection, early diagnosis and early treatment, and cannot be careless. Third, calf pain, one is caused by wearing high heels for a long time, patients should rest first and try to change to flat shoes. Fourth, other common factors are tendonitis, muscle injury, etc. Fifth, varicose veins in the lower limbs can also cause leg pain and may be accompanied by nocturnal leg cramps and local edema, in which case the specific condition of the patient should be decided for conservative treatment or surgery.