Is there adequate space for your knees and legs under the work surface? If not, this lack of space may reduce your ability to change posture, leading to prolonged static postures, which can reduce overall blood flow. Inadequate space also often leads to leaning, twisting, and extended reaching. This can lead to discomfort in essentially the whole body.
At times, the desk or keyboard tray can cause Contact Stress and pressure on the thighs which can reduce blood flow and contribute to discomfort.
Move items out from under your desk that are unused or may be limiting your leg/foot space and make sure the height of your keying/ mousing surface is not resting on your thighs.