Source: Wrestling Observer Newsletter
-- Undertaker was noticeably limping in the ring during certain spots in his matches on the overseas tour last week as one of his knees is bothering him. Taker had arthroscopic surgery during his time off and his knee was in worse shape than first thought. Additionally, he's in the beginning stages of arthritis. Following surgery, the expectation was that he'd be ready to return for good at his Hell in a Cell match with Edge at SummerSlam, but he took a few more weeks off from doing anything physical. Despite the lingering injury, he's still being booked on house shows in tag matches and his TV taping dark matches are usually kept short. It's been noted that he's often in tremendous pain backstage, but never complains about it and usually doesn't show it in the ring.
It's been tossed around that the knee injury is about but it seems like the day is nearing to when Taker will be retiring.
