The following diseases may exist when the legs hurt at night: 1. Peripheral neuropathy, such as the presence of lumbar disc herniation or sciatica, which may aggravate the stimulation of the nerve roots when lying down or in a particular sleeping position, and then cause pain in the lower limbs. 2. Peripheral vascular disease, if patients have deep vein thrombosis or thrombo-occlusive vasculitis, such diseases may cause pain in the lower limbs at night when the blood flow slows down. The pain in the lower extremities is easily induced by the slowing down of blood flow. 3. osteoporosis, which is most common in elderly people with osteoporosis, especially at night when lower extremity pain or cramps occur. 4. old injuries, such as some previous lower extremity fractures or soft tissue contusions, which may leave pain at night after recovery. 5. overexertion, many patients do strenuous work during the day. During the daytime, they do strenuous activities, and at night when they sleep, they may produce lower limb muscle pain.