a bone in your leg
bone in (one's) leg
obsolete An invalid or fictitious excuse for being idle or lazy. You don't want to dance? Why, is there a bone in your leg?
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
a bone in your leg (or head)a (feigned) reason for idleness. informal
Farlex Partner Idioms Dictionary © Farlex 2017