Ryan Kerrigan undergoes knee surgery

Washington Redskins star Ryan Kerrigan underwent arthroscopic knee surgery on Tuesday, leaving his off-season activity in doubt.

The Redskins begin their organised team activities next week, before holding a mini-camp between June 16 and 18.

"It was cautionary to make sure it's not a problem down the road," Kerrigan told ESPN.

He added that the knee needed to be "cleaned up", and will be re-evaluated next week to determine when he is able to resume training.

Kerrigan is entering the final year of his contract, although general manager Scot McCloughan has previously hinted at an extension.