Sabathia underwent an MRI Sunday and had fluid drained from the knee Monday. He was subsequently placed on the 15-day disabled list.
The team is hopeful that Sabathia can return at the end of his DL stint.
"I know he saw Dr. Andrews," Yankees manager Joe Girardi said. "I think he agreed with the MRI. It's basically rest, get it to calm down and see when we can get it out there."
Sabathia has a 3-4 record, 5.28 ERA and 48 strikeouts this season for the Yankees. He has lost his last three starts, giving up 10 earned runs in 14 innings pitched in that time frame.
The team's rotation has been set back because of injuries to Ivan Nova, who is out for the year after undergoing Tommy John surgery, and Michael Pineda, who is on the disabled list with a strained back muscle and won't be back for at least a month. VERDUCCI: As Fernandez goes down, here's a solution to arm injury epidemic