Researchers don’t know exactly what causes phantom limb pain. One possible reason is that nerves in parts of your spinal cord and brain “rewire” when they lose signals from the missing arm or leg. So they send pain signals, a typical response when your body senses something is wrong.
Another example of this rewiring: When you touch one body part -- say, your hip or your forearm -- your brain might sense it on your missing limb.
Other possible causes of phantom limb pain include damaged nerve endings and scar tissue from the amputation surgery.