There may be several reasons for one leg to go numb while sleeping: 1. lumbar disc protrusion, when the lumbar disc protrudes the protruding disc compresses the nerve root, which can lead to pain and numbness in one leg while sleeping. 2, lumbar spinal stenosis, when the lumbar spinal stenosis, the protruding disc and proliferation of bone spurs can also compress the nerve root and lead to the symptoms of numbness in one leg, then the relevant lumbar spine X-ray, CT, MRI examination to diagnose and treat. 3, pear-shaped muscle syndrome, pear-shaped muscle syndrome can appear This is caused by the compression of the sciatic nerve. Early diagnosis and early treatment should be made by early physical examination and neuromyography.