Corbisiero injury a concern for England

London Irish coach Brian Smith admitted England prop Alex Corbisiero is struggling to be fit for the Six Nations campaign as he battles with a recurring knee injury.

Corbisiero started England's recent Tests against South Africa and New Zealand, but he faces a race against time to make the Six Nations kick-off against Scotland at Twickenham on February 2 following his latest injury set-back.

The 24-year-old, who has 16 England caps, was selected to start Saturday's 18-12 Premiership win at Gloucester, only to withdraw at the last minute because of persistent knee trouble and Smith later revealed the injury is a significant problem.

"It is very frustrating for us, it is very frustrating for 'Corbs'. It is a tough time for him, and it is a difficult one to balance," Smith said.

"His knee is a mess. He has played one-and-a-half games for us this season, and it is very disappointing.

"Sitting here right now, I couldn't tell you if he is going to play next week or not. He has got degenerative knee issues.

"He trained twice this week. We are bringing him back, and then at the captain's run he pulled out prior to it, and we had to make a change.

"There is not much of a decision to make when a bloke's knee has blown up and he feels he can't play."