Ireland's Harrington, a three-time major winner, had keyhole surgery to remove cartilage from the knee three weeks ago.
He said on Tuesday that despite some lingering effects, it wouldn't affect his game when the US Open begins on Thursday.
"It has responded well, I'm comfortable," said Harrington, who will play the first two rounds in a marquee pairing with Masters champion Phil Mickelson and PGA Champion Yang Yong-eun of South Korea.
"While it needs a certain amount of minding, and I have to look after it, it's not posing any problem to me playing golf." Harrington said the knee still required icing and physical therapy.
"Maybe I'm not going at it as hard as I could because of that, but, you know, that's not needed, either," he said.
"It's delicate, but it's not inhibiting me." Harrington was more than satisfied to complete 72 holes at the US PGA Tour event in Memphis last week, despite closing with a 73.
With that test passed, he has his sights set on getting back to the winner's circle.
"I'm pretty keen to try and get another win," said the Irishman, who won back-to-back British Open titles in 2007 and 2008 and the US PGA Championship in 2008.
He hasn't won since, but admits the dearth of major success weighs more heavily.
"When you win tournaments like that you want to get out there and get another one," Harrington said.
"I haven't won at any regular events either, but at times I can be distracted at those events and maybe focusing my goals elsewhere."
He doesn't expect that to be a problem as he tackles the par-71, 7,040-yard Pebble Beach Golf Links this week, but Harrington admitted that he would need something to click in his game if he is to go all the way.
"Am I capable of winning? Yes," he said. "I've probably shown better form coming into this major than I have for any of the three I've won.
"But it does need to kick into place. It's not like I'm carrying in unbelievable form, I'm just trying to hold it together this week and get through one more week.
"I am looking for something to fall into place and to get me across that line. I'm hopeful, rather than expectant."