Was asked a question for the June, 2013, issue of Maxim magazine about painful injuries to cold hands. Here is what they printed:
There are several reasons that contribute to that awful pain you feel when you injure cold hands, or cold feet for that matter. With cold temperatures, the body shunts blood away from the extremities, the hands and feet, to preserve warmth to the body’s core and brain. This causes the hands to shrink ever so slightly, you notice it when your rings get loose, and, in doing so, put a bit of extra pressure on the many nerve endings in the hands. That irritates them a bit, making them more sensitive, more likely to signal pain, than when warmer. Also, the muscle fibers tighten with the cold, making the hands stiffer, and more likely to suffer injury if traumatized. Now, if you are really cold, you might even start having frostbite, with direct injury to the soft tissues of the hands, but that would be an extreme case. Certainly wearing gloves helps keep your hands warmer and more protected, but wearing a hat in cold weather is also essential. The hat helps keep your head, and brain, warm, lessening the amount of blood the body has to shunt to the head to preserve the brain, and allowing a tad more to be available to the extremities.