June 9 was a good day for the Boston Red Sox. They won their sixth straight game, finishing off their second straight sweep of the Yankees in the Bronx.

And yet they couldn’t have known then just how good the day was for the organization.

June 9 was when Dustin Pedroia had his knee scoped in Boston, causing him to miss the Yankees finale. Rumors suggested he might need surgery. Instead, Pedroia learned his knee was fine, and since then, he’s been riding what is almost certainly the hottest hitting streak of his career. Since that day, the second baseman has a .469 on-base percentage and .708 slugging percentage for a 1.177 OPS. The OBP is tied with Minnesota Twin Michael Cuddyer’s for the best in the majors in that span. The other two figures are tops in baseball over that stretch.

He homered for the third consecutive game Saturday, a stretch where he had gone deep in six of his last nine games. He had never before had a power surge like this. In fact, he’s never hit more than six home runs in a single month. He has two weeks to best that this July.

Sure, Pedroia has gone on absurd hot streaks before. There was the one in May 2007, when he hit .461 with a .506 on-base percentage for 23 games (with an identical 1.177 OPS). He won the MVP in 2008 with the help of a two-month stretch from late June through August during which he batted .391. And just before his broken foot last June, Pedroia had 23 hits and four home runs in 44 at-bats.

But none of them quite compare to this run, complete as it is with power and endurance.

So what’s been the difference for the second baseman, who until these last six weeks was hitting a disappointing .247?

It starts with peace of mind. Statisticians speak a lot about arbitrary end points; while Pedroia may be the best in the league since his return on June 10, he isn’t necessarily the best since June 8 or June 12. In this case, however, the date is significant, considering it’s when Pedroia returned from learning he wasn’t doing any extra damage to his right knee.

“I think the knee thing really was a load on his mind,” hitting coach Dave Magadan said. “He was concerned he was making it worse and it was going to affect the rest of the season for him. When he got word that he wasn’t going to make it any worse and the procedure he had done alleviated some of the pain, at that point it cleared his mind. From that point, he was off and running.”

Indeed, after missing one game to have his knee checked out, Pedroia posted back-to-back three-hit games in Toronto. He hasn’t stopped hitting since.

“That helps. My knee feels great, my foot’s feeling good,” said Pedroia. “I’m not doing as much rehab stuff, which is great. It takes some pressure off you. It’s been good.”

But self-assurance isn’t the only thing that’s turned Pedroia’s season around. He and Magadan spent a lot of time in May and June working on mechanical flaws in Pedroia’s swing that may have resulted from last year’s foot injury. It took a while for those changes to manifest themselves on the field.

“He had some things going on mechanically early in the season,” said Magadan, alluding specifically to Pedroia’s uncharacteristically high rate of swings and misses. “I think the first month and a half of the season he had already swung and missed more than he had all last year.”

Before having his knee checked, Pedroia swung and missed 82 times at 1,138 pitches — a rate of 7.2 percent. Since, he’s nearly halved that frequency down to 3.8 percent. The result has been fewer strikeouts and even more walks. The second baseman struck out 39 times in 59 games before June 9; that’s down to 10 in 40 games since.

“Little by little, he made the adjustment, and he’s where he should be now,” Magadan said. “Once we got those mechanical issues resolved and the physical maladies he was going through cleared his head, he’s a different hitter right now…. Now he’s getting his pitch to drive and he’s doing something with it. I think he’s in a good place.”

Pedroia’s ability to get on base is perhaps even more important. Pedroia has already drawn 64 walks this season, 10 shy of his career-high set in 2009. Consequently, his .400 on-base percentage (fifth in the A.L.) is 26 points higher than his career pace.

“I’m just trying to get on base for Gonzo and Youk and David,” Pedroia said. “That’s me and (Jacoby Ellsbury’s) job, so we’ve got to continue to do that to be a good offense.”

“Pedey has the rare ability to get hotter than anybody I’ve ever seen, almost,” manager Terry Francona said. “Fortunately it looks like he’s wanting to do that. He can go on these runs where it doesn’t matter what you throw him. He looks like he’s starting to get to some balls he didn’t earlier.”