Dave and his doc perform "Seven Nation Army".

"Holy shit, that’s actually my doctor. What a badass!" That was what Foo Fighters frontman Dave Grohl had to say after his orthopedic surgeon, Dr. Lew Schon, performed the White Stripes' "Seven Nation Army" onstage with the Foos during their July 19 show at Boston’s Fenway Park. Dr. Lew not only impressed Grohl, but his rousing performance (which you can watch above) had the crowd yelling "Lew," in a way similar to Bruce Springsteen fans adoringly yell "Bruce."

Before the song began, Grohl told those in attendance how Dr. Lew came to be onstage with them that night. "My orthopedic doctor is here tonight okay," explained Grohl. "The man that made it possible for me to get onstage and play a show tonight. Now, he came to my hotel room today and he f–king checked out my leg and he said, ‘You can rock Fenway tonight’ and I said, ‘Lou, so can you.'"