London Wasps scrum-half Joe Simpson has been ruled out for up to a month with a knee injury.

The 24-year-old England international suffered the problem during his side's victory over London Welsh in the Aviva Premiership on Sunday.

"Thankfully it doesn't look like it needs an operation," said Wasps director of rugby Dai Young.

"At the moment he is looking at around three, four weeks of rehab, which is much better than we first thought."

Wasps continue their league campaign away to second-placed Saracens on Sunday.