The main causes of thigh numbness after prolonged sitting are.
Sciatic nerve numbness, normal people sciatic nerve from the sacral plexus, through the pear-shaped muscle, to the rear of the lower limbs, when sitting, the sciatic nerve is under tension, generally will not produce numbness, feeling abnormal. However, too much time (especially unilateral exertion resulting in excessive pulling of the pear-shaped muscle) will lead to excessive tension of the sciatic nerve and excessive compression by the pear-shaped muscle, resulting in abnormal sensation in the thigh.
Ischemic. After prolonged sitting, the blood vessels in the lower extremities are compressed, leading to nerve and tissue ischemia, resulting in numbness.