Complex Regional Pain Syndrome (CRPS) is a term used to describe a group of painful conditions. Earlier names for these conditions include Reflex Sympathetic Dystrophy (RSD), causalgia, etc. The pain in CRPS is constant and either shooting, sharp, or burning. The pain may be severe and it lasts much longer. Few people may not have a history of an injury or surgery before the pain started, but mostly people have such a history, when explored in detail.
CRPS can happen to anyone at any age. Females in their 40s to 60s are more likely to get it. CRPS isn't the same for all people. Many have mild symptoms which slowly get better over time. But some people may not recover as expected.
The injury might also be caused by an accident, a fall, or surgery. In few people, CRPS starts without an apparent reason. It isn't clear why some people get CRPS while others do not.