Sources: 49ers' Bush has torn MCL, to undergo season-ending surgery

San Francisco 49ers running back Reggie Bush will undergo season-ending surgery on his torn MCL on Tuesday, sources told ESPN NFL Insider Adam Schefter.

Bush, whose ACL was deemed OK after tests were negative, was carted off the field with a left knee injury Sunday, after he slipped on concrete near the stands in St. Louis on a punt return.

Bush planted both feet on the concrete and landed on his backside while slowing down after being shoved out of bounds by Benny Cunningham after a punt return in the first quarter. He slid into the padded wall of the stands, but not at a particularly high speed.

He did not return. After the game, Bush said, "Trying to stay healthy has been an issue this season."

Bush entered Sunday's game against the St. Louis Rams with just eight carries for 28 yards and a long gain of 9 yards.

Bush made his first start since Dec. 28, 2014, for Detroit against Green Bay. His last 100-yard game was Nov. 28, 2013, when he had 117 yards against Green Bay.