Low back pain, back pain, and combined leg weakness may be caused by the following reasons: First, there may be diseases of the lumbar spine, commonly lumbar disc herniation, lumbar spinal stenosis, or lumbar spondylolisthesis, which compress the nerve roots of the lower extremities, resulting in neuropathic pain, numbness, and weakness of both lower extremities. At the same time, there is also a combination of lumbar and back muscle soreness and pain, and even with limited movement. Second, the symptoms may be caused by viral infection, which invades the muscles and joints of the whole body through blood circulation. Usually, in addition to back pain, leg pain and weakness, there are also symptoms of upper respiratory tract infection, such as nasal congestion, runny nose, cough, coughing, dry throat, sore throat, and even fever in some patients.