The main causes of lumbar and leg swelling and pain include lactic acid accumulation after strenuous exercise, lumbar disc herniation, and third lumbar transverse herniation syndrome. 1. Lactic acid accumulation: If the patient has performed a lot of strenuous exercise before the symptoms appear, the lactic acid in the body is too much and can not be metabolized and absorbed, it will gather in the waist and legs. The specific manifestation is waist and leg pain, weakness, and even swelling. After proper rest, the symptoms will disappear. 2. Lumbar disc herniation: Lumbar disc herniation and lumbar spinal stenosis may be caused by prolonged sedentary activities, because the lumbar disc annulus fibrosus is weak or ruptured, resulting in the nucleus pulposus protruding and compressing the nerves backward. Symptoms include swelling and pain in the lower back and legs, sometimes accompanied by sciatic nerve pain. 3. Third lumbar transverse process syndrome: Third lumbar transverse process syndrome is a series of symptoms caused by chronic strain injury caused by thickening of the fascia around the third lumbar transverse process, which compresses the nerves that pass through the fascia. Typical manifestations include lumbar muscle pain, swelling and pain on the inner and outer sides of the thighs. In addition, rheumatic diseases or joint diseases may cause low back and leg pain. Therefore, it is recommended that patients with lower back and leg pain should go to the hospital as soon as possible for examination, and take appropriate treatment and relief methods according to the results of the examination.