Welcome,
have you read anything about RSD or CRPS?
It can set in after even a small injury or surgery.
you can read about or ask questions on our forum
Reflex Sympathetic Dystrophy
Reflex Sympathetic Dystrophy (Complex Regional Pain Syndromes Type I) and Causalgia (Complex Regional Pain Syndromes Type II)
http://neurotalk.psychcentral.com/forum21.html