The Northern Irishman, out of action since he ruptured a ligament in his left ankle while playing football with friends on July 4, does not have to commit to the tournament, which starts on Thursday, until his official tee time for the opening round.
World number one McIlroy has been grouped with Masters and U.S. Open champion Jordan Spieth and British Open winner Zach Johnson for the first two rounds of the year’s final major at Whistling Straits in Kohler, Wisconsin.
“Great 18 holes this morning with haza136 @ Whistling Straits Golf Club,” McIlroy tweeted, referring to his good friend and playing partner Harry Diamond.
According to Golf Channel, McIlroy said after his round that he has now played 90 holes of golf since recovering from his ankle injury.
Should he tee off as expected on Thursday, it would be just 40 days since he suffered an injury that some medical experts said might take about three months to heal.
It also would be more than seven weeks since McIlroy tied for ninth in the U.S. Open at Chambers Bay and would give the PGA Championship a huge boost as he and Spieth share top billing.
The 26-year-old Northern Irishman withdrew from the July 9-12 Scottish Open after suffering the ankle injury and was unable to defend his British Open title the following week at St. Andrews.
Over the past week, McIlroy has posted a string of teasing videos and messages on Twitter and Instagram highlighting his recovery progress.
On Thursday, he posted on his Instagram account a video of himself pounding a driver on a practice range in Portugal, accompanied by the comment: “Feels good to hit the driver again!”
He also posted two pictures of his left foot, the first showing a very swollen ankle soon after he had suffered the injury and the second revealing a bruised but greatly improved ankle.
“4 and a half and 3 and a half weeks ago respectively… I’ve come a long way since,” McIlroy tweeted.
On Friday, McIlroy hinted strongly at his journey to Whistling Straits by posting a picture of the interior of a private jet with a British passport front and centre on a table.
After a strong start to the 2015 season highlighted by three wins, McIlroy showed signs of fatigue when after a runaway victory at the Wells Fargo Championship in North Carolina, he missed the cut at two European Tour events in May.
Those missed cuts came at the end of a run of five successive tournaments.
McIlroy won last year’s PGA Championship by one shot after a final-round shootout that finished in near darkness at Valhalla Golf Club in Louisville, Kentucky.
(Reporting by Mark Lamport-Stokes in Akron, Ohio; Editing by Andrew Both/Larry Fine)