The Celtics were well aware that Nate Robinson was dealing with knee issues when they traded him to the Thunder last month.

Robinson will miss four-to-six weeks of action after undergoing arthroscopic surgery on his right knee Friday.

"We knew about it," Boston coach Doc Rivers said. "The Nate injury, I knew he was having knee pains, but other than that I didn't know much about it. [Kendrick Perkins] we knew, obviously. He got hurt in the game against [the Warriors], so we knew he'd be out for a little bit."