United Kingdom, Sept. 26 -- Robert Plant is having a knee replacement operation.

The 77-year-old rocker admitted years of performing on stage has taken a toll on his body and he is set to go under the knife to get one of his joints replaced because he can no longer play sport.

Explaining why he has been using a walking stick, he told The Sun newspaper: "Ooh! I'm having a knee replacement next week.

"It's all the years of standing on stages. Well, either that or the tennis, which I can't play any more."

The Led Zeppelin frontman also paid tribute to the late Ozzy Osbourne following his death in July at the age of 76 and praised the Black Sabbath singer for the "world of craziness" he created.

He said: "I loved him. I thought it was gr...