Explicación
This joke plays on the double meaning of the word ‘cast.’ Originally, saying ‘break a leg’ to an actor is a way of wishing them good luck without jinxing their performance. On the other hand, ‘cast’ refers not only to the group of actors in a play but also to the hardcovering used to support and protect a broken bone. So, the humor emerges from the literal interpretation of ‘breaking a leg’ leading to being part of a ‘cast,’ both in the play and medically.
