WWE posted the following :

Seth Rollins’ right knee was re-injured during Samoa Joe’s ambush at the conclusion of this Monday’s Raw, WWE.com can now confirm. The attack occurred as Rollins was heading to the ring to finally confront Triple H, who cost The Architect a WWE Universal Championship opportunity back in August.

Rollins commented on the injury via Twitter, posting a photo of his knee undergoing examination.

Full story and video of Rollins leaving RAW at the link below :

http://www.wwe.com/shows/raw/article/seth-rollins-injured-samoa-joe