Correct a leg bone (7)

I believe the answer is:
apropos
'bone' is the definition.
Both the definition and answer are adjectives. Maybe there's an association between them I don't understand?
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for apropos that I've seen before include "Concerned with" , "fitting" , "well-chosen" , "Appropriate" , "Suitable or relevant" .)