The inability to extend fingers (loss of extension) can occur after trauma or develop spontaneously. In some people the finger can be straightened passively but not actively, in others the loss of extension is not correctable at all.
Questions to ask are whether the loss of extension is intermittent or is it permanent and/or progressive?
Can you ever straighten your finger?
YES
NO
Has this followed an injury?
No - see:
dupuytrens disease