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Friends of famed exercise guru Richard Simmons are worried about him, claiming he has a crippling depression and he's not been seen in almost a year.

Known for his peppiness regarding fitness, the "Sweatin' To The Oldies" host has gone M.I.A. on friends, refusing to accept phone calls and allow people to enter his home, TMZ is reporting. Once a mainstay at his famed Slimmons studio in Beverly Hills, Calif., Richard has also not been seen there in months.

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Richard, TMZ is reporting, "is in a massive state of depression over a bum knee." Quoting one of the few people that Richard still talk to, the website said the fitness junkie needs a left knee replacement and if he doesn't get one he will never be able to exercise again.

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Quite simply, Richard is "terrified" of knee surgery, so much so that he's been putting it off.

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"He's been paralyzed with fear and depression," TMZ said.

Some friends, however, told the website that they think the issue is more serious than a knee issue, but didn't go into detail.

Richards last public appearance was in January 2014.