Vince McMahon returned to work during last week's RAW on 10/3 after he tore his quad. He has been known to no-sell being hurt or sick, and some people backstage are saying he wasn't even using crutches or anything. He did, however, have a brace on his leg.
It's not the first time McMahon tore his quad and then returned fast. He did so when sliding in the ring during the finish of Royal Rumble back in 2005.