Barcelona defender Gabriel Milito will undergo surgery on his injured right knee and is expected to be sidelined for six months, the Spanish club has revealed.

The 27-year-old Argentinian complained of pain in his knee after Barça's 1-0 UEFA Champions League defeat by Manchester United last week and tests confirmed he had twisted a ligament, the club's medical services said in a statement. "We have determined arthroscopic surgery next week as a solution to the problem," the statement said.

Milito has made regular appearances for Barcelona since he joined the club from Real Zaragoza for 20 million euros in July 2007.