LOS ANGELES - For more than a decade, Zach Eflin's knees have hurt. The 22-year-old pitcher learned to manage the pain with hot-and-cold contrasts, hip stretches, core exercises - anything to relieve the tension on his knees. It worked until Tuesday, when he woke up after allowing seven runs in three innings, and the pain was too great.

The patellar tendinitis in the rookie righthander's knees forced him to the disabled list, and there is little known beyond that. The Phillies are not sure whether Eflin will pitch again this season. When the team returns home Thursday, doctors will perform some studies on his knees.

He is a 22-year-old man with bad knees, and he does not know what to expect.

"It's pretty confusing," Eflin said. "I'm confused, too."

The Phillies were aware of Eflin's condition at the time of the December 2014 trade to acquire him. They have treated him ever since. That plan thrived as Eflin proved himself at triple-A Lehigh Valley and ascended to the majors with success.

He threw a shutout on July 22 against Pittsburgh. He has a 13.85 ERA in three starts since. On Monday night, after Eflin lasted just three innings against the Dodgers, he said the knees did not affect his performance on the mound.

A day later, he admitted it was time to rethink the plan.

"I've been dealing with knee soreness for years," Eflin said. "This year has kind of been more relevant than previous years. . . . I've had it my whole career. I've gotten treatment my whole career. And it's getting to be a little much right now. I woke up this morning and they were pretty stiff and sore."

Phillies manager Pete Mackanin described Eflin's injury as a "chronic issue." Chase Utley was beset by patellar tendinitis in his twilight years with the Phillies, but Mackanin said he was not certain that Eflin had the same condition (chondromalacia) that Utley did.

"I'll leave it up to the medical people," Mackanin said. "I don't know how they're going to handle it."

Eflin was the second young Phillies starter to be placed on the disabled list in less than a week. Aaron Nola is still shut down from throwing, Mackanin said, and it is possible that he does not return this season. Eflin, who at least has not injured his elbow or shoulder, could be subject to the same restrictions.

The Phillies will impose innings restrictions on Vince Velasquez and Jake Thompson. That, plus the recent injuries, has Mackanin wondering how the team will survive the final seven weeks of the season.

"I mean, we'll get it figured out," Mackanin said. "But we're going to have to put some thought into it and see what happens."

He added: "We're not in a tizzy right now, but we're in a quandary."

Either Adam Morgan or David Buchanan could replace Eflin, whose next scheduled turn is Sunday. Both have pitched well at triple A and have experience in the majors. The Phillies will need both of them to fortify the rotation in September.

Righthander Ben Lively is another option; the prospect acquired from Cincinnati for Marlon Byrd has posted a 2.65 ERA in his last six starts with 31 strikeouts and 10 walks in 371/3 innings. Lively, 24, is not on the 40-man roster, but he must be added this winter for protection from the Rule 5 draft.

Eflin said the pain in his knees started when he was 11 or 12 years old. But it has never been worse than what he's felt this season.

Is he worried?

"We'll see," Eflin said. "I really don't know what to expect. Like I've said, I've had it for so long. It's always been tolerable. It's always been maintainable. I guess we'll see what happens."

@mattgelb