Dennis and Judi were discussing dupuytren contracture on the show and Dennis mentioned how he used to use his double jointed thumb as an excuse to get out of gym class when he was a kid. When Dennis would bend his thumb backwards it resembled dupuytren contracture.

Take a look at Dennis' hand when he would pretend he was injured to get out of gym class as a kid.

Judi Franco

There also was a character played by Chris Elliot in the movie 'Scary Movie 2' that suffered from a hand condition. It has not been confirmed to be dupuytren contracture, but it looks similar.

Warning: NSFW Video