(Jonathan Newton/The Washington Post) (Jonathan Newton/The Washington Post)

DENVER — A day after star outfielder Bryce Harper visited orthopedic surgeon James Andrews for a second opinion on his swollen left knee, the Washington Nationals said Andrews reaffirmed the team medical staff’s original diagnosis of patellar bursitis, adding that there is no structural damage to the knee. Harper received a platelet-rich plasma (PRP) and cortisone injection into the bursa sac, Nationals trainer Lee Kuntz said Tuesday, and could resume baseball activities in a week if the swelling subsides.

Kuntz said the cortisone is expected to help reduce the inflammation and the PRP injection, spun from Harper’s own blood cells, is for any potential infection and help protect the knee. The decision to administer the injections was made jointly by Andrews and the Nationals’ team physician, Wiemi Douoguih, who made the original diagnosis on Harper’s knee. Harper hasn’t played since he aggravated the knee injury on May 26; the original injury occurred in a May 13 collision with the right field fence in Los Angeles.

The large brace Harper was spotted wearing in the airport after his visit with Andrews was to immobilize and rest the knee, Kuntz said. Harper’s agent Scott Boras said Tuesday that the outfielder did not undergo surgery, a fact the Nationals reiterated.

“These are all good things,” Kuntz said. “We want him to rest the knee, that’s why we put him in the immobilizer. We’ll reevaluate him in one week’s time and if everything’s a go then we will resume activity with him and get him going as quickly as we can.”

Harper, who was originally opposed to receiving a cortisone shot, will remain in Washington during the Nationals’ nine-game road trip. The Nationals are 6-12 without Harper in the starting lineup.

“I want to play already!” Harper wrote in a tweet during Tuesday’s game. “Can’t sit here and watch my boys out there! Miss being on the field! #DLsucks”

The Nationals hope Harper’s knee will be able to hold up for the duration of the season with this course of treatment. Kuntz appeared unwilling to address what would happen if Harper’s knee doesn’t respond to the  injections.

“That’s a bridge you’ll cross when you come to it,” Kuntz said. “[Doctors] tell the player always risks and benefits of things and all of this was positive things for Bryce. Just rest this, we’ll see how it responds and we’ll go from there.”

It’s unclear what prompted Harper to agree to the cortisone shot. Harper rejected the treatment last week: “I don’t want to put any of that stuff in my knee or in my body. I think that can do some damage to my knee. I’m not going to do that at 20 years old.”

Harper’s father, Ron, said he and his son had discussed the possibility of a cortisone shot as one possible outcome of the visit with Andrews. Those close to Harper put no pressure on him to receive a shot, leaving the decision up to him. It appears Harper, who has been itching to return as the team’s offense has continued to slump, may have seen the cortisone shot as a quick way to get healthy and reduce the swelling.

Tuesday’s news reflected what the Nationals believed all along about Harper’s injury. General Manager Mike Rizzo said over the weekend that he had “no worry” that the visit to Andrews, the surgeon who operated on the right knee of Washington Redskins quarterback Robert Griffin III, would reveal structural damage and that it was a matter of procedure to seek a second opinion. Once the swelling decreased, the Nationals believed the outfielder could return to play and not risk further damage.

Despite not playing since May 26, the swelling hadn’t subsided much and, after it increased following a light workout in the pool Thursday, the Nationals scheduled Harper’s appointment with Andrews. In recent days, however, Nationals officials said Harper’s inflammation had subsided. Harper must wear his immobilizing cast daily and moving around.

Harper first injured his knee May 13 in Los Angeles, when he crashed into the Dodger Stadium fence while chasing a fly ball. The day after, Harper received X-rays on his left knee and left shoulder, and Rizzo described Harper’s status as “day-to-day.” Harper pinch-hit two days later on May 15 and started May 16. He bounced in and out of the lineup until May 26, when he aggravated his left knee with two headfirst slides and with a foul ball off his knee.

After an MRI the Nationals diagnosed Harper with bursitis, a heavy swelling of one of the knee’s bursa sac. He sat out the next five games, and the Nationals placed him on the 15-day disabled list June 1. Harper admitted the following day he should have landed on the disabled list after an April 30 hit against the right field wall in Atlanta which bruised his left side.

Harper’s father has said he and his son feel the Nationals handled the outfielder’s injury appropriately.

“I wish he was out there right now playing,” Manager Davey Johnson said. “Injuries, it’s a tough thing.”

Adam Kilgore contributed to this report.