has been out of the public eye for nearly a year, causing rumors to spiral that he's ill or depressed.
The 66-year-old fitness enthusiast was last seen publicly at a Covered California event in January, where he posted an adorable smiley pic. This hiatus from the public eye has been troubling to fans, prompting an outpouring of support, including a message from Erin Murphy, who played Tabitha on Bewitched.
"Thinking about my pal Richard Simmons, who isn't doing too well," she Tweeted
Fortunately, we have learned that Richard is safe, but sources tell us that he has been feeling low because of a knee injury that has left him temporarily unable to exercise.
"Richard Simmons has been sidelined with a knee injury for the past several months," Michael Catalano, Richard's long-time manager, tells ET.
Having undergone knee replacement surgery on his right knee four years ago, sources tell us he's frightened and depressed about having to undergo the surgery all over again for his left knee.
But Simmons kept things upbeat and positive in a Facebook page
: "I am so touched by the outpouring of love and concern I have received today. I have had a tough time dealing with this injury, as it is keeping me from doing what I truly love to do and that is to teach classes around the world. Keep on Sweatin'!"
We're rooting for you, Richard!