Sitting for a long time leg numbness may be temporary nerve compression and other physiological reasons, may also be trauma, lower extremity vascular disease, lumbar spine disease and other pathological reasons. 1. Physiological reasons: sitting for a long time can cause temporary compression of the sciatic nerve and femoral nerve, which can cause numbness of the legs, and most of them can be relieved after activities. 2. Trauma: Bone and soft tissue injury due to trauma, local swelling, sedentary can compress the nerves innervating the lower limbs, thus causing symptoms of leg numbness. 3. Lower extremity vascular disease: mostly seen in lower extremity varicose veins and other diseases, due to sitting for a long time can aggravate the poor circulation of the lower extremities, nerve ischemia, hypoxia, edema and other changes, can appear the symptoms of numbness of the legs. 4. Lumbar spine disease: due to lumbar disc herniation and other diseases stimulate or compress the lower limb nerves, sitting for a long time can aggravate the compression, which can lead to leg numbness and other symptoms. Sitting for a long time leg numbness may also have other reasons, it is recommended to go to the hospital in a timely manner, improve the examination to clarify the cause of the disease, give targeted treatment or treatment.