* Barca say knee is bruised pending further tests (Adds Barca statement)
BARCELONA, Dec 5 (Reuters) - Barcelona's Lionel Messi was carried off on a stretcher after sustaining what the club said was bruising to his left knee near the end of the La Liga side's Champions League Group G match at home to Benfica on Wednesday.
The Argentine World Player of the Year collapsed to the ground clutching the back of the knee after colliding with Benfica goalkeeper Artur and looked to be in severe discomfort as he was taken from the pitch.
Barca said on their Twitter feed he had suffered bruising on the outside of the knee and would undergo further tests to determine the extent of the damage.
"After beating the offside trap Messi tried to dribble round opposing keeper Artur, who dealt him a blow, but Messi continued with the move," Barca said in a statement on their website (www.fcbarcelona.com).
"After shooting with his left foot the player fell to the ground with pain in his left knee," the statement added.
"The player is now in the Nou Camp dressing rooms being treated by club medical staff."
The game ended 0-0 with Barca already through to the last 16 as group winners and Benfica forced to settle for a place in the Europa League.
Messi remains one goal short of Gerd Mueller's record of 85 goals in a calendar year set in 1972. (Reporting by Iain Rogers, editing by Ed Osmond and Alison Wildey)