Causes

The cause of CRPS isn't completely understood. It's thought to be caused by an injury to or an abnormality of the peripheral and central nervous systems. CRPS typically occurs as a result of a trauma or an injury.

CRPS occurs in two types, with similar signs and symptoms, but different causes:

• Type 1. Also known as reflex sympathetic dystrophy (RSD), this type occurs after an illness or injury that didn't directly damage the nerves in your affected limb. About 90% of people with CRPS have type 1.
• Type 2. Once referred to as causalgia, this type has symptoms similar to those of type 1. But type 2 CRPS occurs after a distinct nerve injury.

Many cases of CRPS occur after a forceful trauma to an arm or a leg. This can include a crushing injury or a fracture.

Other major and minor traumas — such as surgery, heart attacks, infections and even sprained ankles — also can lead to CRPS.

It's not well understood why these injuries can trigger CRPS. Not everyone who has such an injury will go on to develop CRPS. It might be due to a dysfunctional interaction between your central and peripheral nervous systems and inappropriate inflammatory responses.