Manchester United midfielder Marouane Fellaini has announced his retirement from football after being diagnosed with a serious knee injury.

The Belgian international, who joined the club in 2014 for £35 million, had been expected to play a key role in the team's title challenge this season.

However, he was forced to withdraw from the squad due to a recurring knee problem and eventually underwent surgery earlier this month.

In a statement released by Manchester United, Fellaini said: "I've always dreamed about playing for a club like Manchester United and I'm proud to have spent five years at Old Trafford."

"I want to thank everyone who supported me throughout my time at the club and wish them all the best for the future."

He added: "I'm looking forward to seeing what the future holds for me and my family."

Fellaini's departure is a blow to Manchester United, who will now be without one of their most experienced midfielders for the rest of the season.

However, the club's manager Ole Gunnar Solskjaer is confident that they can still compete for the Premier League title despite losing one of their key players.

Solskjaer said: "We'll miss Marouane, but we have other players who can step up and fill his shoes.

"We're going to work hard to make sure we're as strong as possible and give ourselves the best chance of winning the Premier League."