Complex regional pain syndrome (formerly known as reflex sympathetic dystrophy or RSD) is a chronic pain condition usually affecting the hand or foot. CRPS is often initiated by some kind of trauma. The trauma does not have to be major.
The pain associated with CRPS is usually present all the time and out of proportion to the original injury. It often feels like a burning sensation and the skin is often very sensitive to touch and to temperature changes. Even light touch is often painful. There may be swelling at times, often in the early stages of the syndrome. You may notice that your nails grow at differentiates and that your skin looks different on the hand or foot that is hurting. The affected area also may be a different temperature from the rest of your body.