Pain at the back of the leg is commonly caused by myofibrositis, as well as lumbar spine disorders that cause radiating pain in the lower limbs, etc. Since the back of the leg is mainly muscle tissue, it is often caused by myofibrositis at the back of the leg after exertion, trauma, and exposure to cold, causing pain at the back of the leg, which manifests itself as localized pain and pressure, and may be aggravated by the pain when the limb is passively pulled and moved. In addition, when lumbar disc herniation, lumbar spondylolisthesis, lumbar spinal stenosis and other lumbar spine disorders, the nerve root in the spinal canal is compressed by the protruding intervertebral discs, hypertrophied ligaments, and hyperplastic bone tissues, and then there will be the radiating pain in the innervated area of the compressed nerves. Since lumbar disc herniation and lumbar spondylolisthesis are most common in the lumbar 4, 5, and lumbar 5-sacral 1 segments, the compression of the lumbar 5-sacral 1 nerve root causes pain at the posterior part of the leg.