Numbness from the knee down to the feet may be caused by peroneal nerve injury, lower limb vascular disease. 1. Common peroneal nerve injury: common peroneal nerve is a branch of sciatic nerve, divided into superficial peroneal nerve and deep peroneal nerve, which jointly innervates the sensation and movement of muscles in the lower leg and foot area. When common peroneal nerve is jammed or damaged, abnormal sensation and muscle strength in the area below the knee may occur, and the common causes of injury are trauma, popliteal cysts, and so on. 2. Lower extremity vascular disease: when the blood vessels innervating the knee and the distal limbs are diseased, it will cause local blood circulation obstruction, venous return obstruction and blood stagnation in the area below the knee, which can lead to ischemia and hypoxia of the tissues in the long run, and the symptom may appear, such as varicose veins of the lower limbs and thrombotic occlusive vasculitis. Numbness from the knee down to the feet may also have other causes, it is recommended to go to the hospital in time to improve the examination to clarify the cause of the disease, under the guidance of the doctor to give targeted treatment or treatment.