Lumbar and knee pain may be caused by compression of the nerve roots distributed in the lumbar and knee, and also by different diseases in the two parts of the body, such as osteophytes and lumbar muscle strain. 1. Nerve compression: If the patient suffers from lumbar disc herniation or lumbar spinal stenosis, it may compress the peripheral nerves and cause lumbar pain, which may also radiate to the lower limbs and cause knee pain. 2. Knee disease: If the patient’s knee is subjected to weight-bearing activities for a long period of time, it may cause bone hyperplasia, which may lead to osteoarthritis, resulting in knee pain. 3. Lumbar diseases: If the patient repeatedly bends over and bears weight, it may cause lumbar muscle strain, lumbar myofasciitis and so on. In addition, if the patient suffers from ankylosing spondylitis, it can also cause significant lower back pain. The causes of low back and knee pain are many and complex, patients should go to the hospital in time for examination to clarify the cause of the disease and receive appropriate treatment.