The most common causes of pain in both legs are the following. 1. lumbar disc herniation. The degenerated disc compresses the dural sac and bilateral nerve roots, or combined with spinal stenosis, there will be pain with numbness in both lower limbs, and muscle atrophy can seriously affect the functional activities of the lower limbs. Lumbar disc CT can clearly diagnose. 2, osteoarthritis. Common in the elderly, especially the knee joint. Because of bone joint degeneration, osteophytes, resulting in joint space narrowing, coupled with prolonged walking inappropriate exercise, easily cause or aggravate the pain of both lower limbs. 3, calcium deficiency. Prolonged hypocalcemia can also easily cause twitching and pain in both lower limbs, with pain occurring mostly at night.4. Strenuous exercise and prolonged strain, with muscles under tension for a long time without rest. A large amount of acids, such as lactic acid, will be produced in the muscles, and these acids will stimulate the muscles to produce pain.