It's something we've all experienced: the back of your elbow smacks against a hard surface and the impact sends a sensation so distinctly disquieting shooting down your arm that it takes several moments to regain composure. So, why does hitting this spot on your elbow— commonly known as the funny bone— feel so weird? Cella Wright explains one of the most complicated joints in the body. Lesson by Cella Wright, directed by Anton Bogaty.