Wayne Rooney left the Manchester United defeat to his former club, Everton, on Sunday with suspected ligament damage to his left knee.

The Telegraph report that Rooney’s injury appears to be to the medial ligament and that details regarding the nature or severity of the problem will not be released by the Old Trafford side until 1st May.

The medial collateral ligament (MCL) goes from the inside surface of the upper shin bone to the inner surface of the bottom thigh bone. The ligament helps keep the inside portion of the knee joint stable. It is usually injured due to pressure or stress on the outside part of the knee.

This often occurs simultaneously with injury to the anterior cruciate ligament (ACL) on the inside of the knee. This doesn’t appear to be the case since Rooney seems to be mobile, having made an appearance at the Professional Footballers’ Association Player of the Year later that evening.

The injury, if severe enough, could put the United striker out of action for up to a month. With only four more games in as many weeks, it would appear that he could be out for the remainder of the season. Rooney would likely be replaced by Robin van Persie, Radamel Falacao, or 19-year-old James Wilson, who has had made two starts and 10 substitute appearances this year.

Arsenal go to Old Trafford on the 17th May for their third showdown with United this year. This would be the second meeting at the Theatre of Dreams this season, after beating United in the FA Cup there on 9th March – for the first time since 17th September, 2006.

The Gunners will be looking to win this to provide further insurance of keeping second place in the Barclay’s Premier League.