Most of the causes of numbness in the thighs during sleep are due to the legs being in a poor sleeping position, resulting in obstructed blood flow back to the nerves, causing ischaemia and resulting in impaired sensation in the local area of dominance, which can usually be relieved by adjusting the sleeping position. If the symptoms are not relieved by adjusting the sleeping posture, it is recommended that a hospital visit is made to further identify the cause.