If you have thigh pain after staying up late, it may be caused by the following reasons: 1. It may be caused by prolonged pressure on the thigh. Some patients in the process of staying up late, sitting in the chair may not be appropriate, or have a bad sitting posture. These two conditions lead to long-term pressure on the thigh area, will produce soreness afterwards. 2, there may be vascular-related lesions. When the human body is sitting or standing for a long time, the blood flow rate of the lower limbs will be very slow, and at this time it is very easy to appear thrombosis of the veins of the lower limbs. If this happens, it will often cause swelling and obvious soreness in the lower limbs. 3, there may be peripheral nerve lesions. In the process of staying up late, the lower extremities are inevitably underdressed or cold, which may cause the joints of the lower extremities, or soft tissues to produce sterile inflammation, which leads to soreness.