You could argue it's not entirely surprising that, five weeks into the season, Kansas City Chiefs running back Jamaal Charles is leading the NFL in rushing yards. After all, Charles did average 6.38 yards-per-carry in 2010 while rushing for nearly 1,500 yards.

But the fact that Charles is on pace for a career season one year after tearing his left ACL is somewhat remarkable. A torn ACL is one of the most devastating injuries in sports, as it almost always sidelines a player for the remainder of the season and can sometimes end a career.

Charles, however, isn't the only running back who is up to speed less than a year removed from an ACL tear. Minnesota Vikings running back Adrian Peterson, who tore his ACL last December against the Washington Redskins, is averaging 84 yards. Rashard Mendenhall tore his ACL in January, and in his first game back for the Pittsburgh Steelers he ran for 81 yards on 14 carries and caught one touchdown pass.

The NFL has a long history of running backs going down with ACL injuries, and different players have come back in different shape. Terrell Davis was never the same after tearing his ACL, whereas Jamal Anderson had some of the best years of his career after his injury.

Much of a running back's ability to return depends on his age. Davis was 27, Lewis was just shy of his 22nd birthday, Charles was 24, Peterson was 26 and Mendenhall was 24. Indeed, if an athlete is young enough and motivated, many think he or she could come back stronger after the surgery than they were before.

The timing of the injury also determines how an athlete will return. Because Charles tore his ACL early in the 2011 season, he had more time to rest and rehab than Peterson or Mendenhall.

"My legs feel fresh since I've been out of football for a year," Charles said before the season. "I feel real good just to be on the field again. I'm blessed."

Follow us on Facebook and Twitter to read them first!

1939 Dodge Still Runs -- As A Grill