Even in pain, Chelsea Handler keeps 'em laughing.

Undergoing knee surgery Thursday, the E! comedienne, 37, was forced to miss that night's taping of her late night series Chelsea Lately, but took to Twitter to assure fans she was OK.

"Fortune Feimster will be filling in as the host on tonight's show with more photos of me and my knee making a quick recovery. Pls support her," the comic wrote on her Twitter page, posting a pic of herself in a hospital bed noshing on graham crackers.

During Thursday's broadcast -- where Feimster interviewed Real Housewives of Orange County's Gretchen Rossi and Tamra Barney -- Handler delivered a pre-taped message kidding around about her hospitalization.

"I just woke up from surgery -- from my vaginal rejuvenation surgery," a groggy Handler cracked.