Richards may be out for season after surgery

Manchester City's England international defender Micah Richards will be out for a number of weeks and may miss the rest of the season after undergoing an operation yesterday on a knee injury that has troubled him on and off for five months.

The initial damage to cartilage in his right knee led to Richards being carried off during City's Carling Cup victory at Bolton in October and, though the initial prognosis was that he had suffered only bruising and he missed only the subsequent league game against Sunderland, the same problem ruled him out of this month's FA Cup defeat at Sheffield United and the draw at Derby County. Yesterday's operation at London's Lister Hospital was deemed necessary after he complained of more soreness on Tuesday morning, following the home defeat to Everton the previous night.

City are desperately hoping that the 20-year-old, who travelled to London with the club physiotherapist Ally Beattie for surgery, will be back before the end of a season which began promisingly but has faded recently and left them struggling for a Uefa Cup place. "It's possible that he will not play [again] this season, though we are hopeful that it will be a few weeks. We will monitor the situation," said a club spokesman.

The recovery time after cartilage surgery is two to four weeks and the injury will frustrate Richards, who also missed out on a 12th England cap in Fabio Capello's side against Switzerland after tweaking his back in training after joining the squad.

The injury was sustained in a clash with the Bolton captain Kevin Nolan and Richards will be ruing his decision to play on with it – exacerbating the problem by catching his studs in the turf. Surgery has been a prospect for weeks. City's medical staff considered it after Richards missed the Derby game but decreed that five or six days' rest could resolve the problem. Richards had a difficult game when he returned against Arsenal, but was back at his best during the win over Manchester United. He had hoped that a five-day break in Tenerife with Joe Hart and friends after the United game would help.

City's club doctor Mark Whitaker said the operation had been "successful" and that Richards, who last month signed a new five and a half year contract believed to be worth £50,000 a week, will begin a rehabilitation programme at the club's training ground today. "The medical team will monitor his progress over the coming days and weeks," Whitaker said.

The prolonged lay-off has echoes of Richards' frustrating end to last season, sidelined by a calf injury.