On the Friday before the Ravens’ playoff opener, coach John Harbaugh declined to comment on the condition of Lamar Jackson’s injured left knee, which the star quarterback on Thursday had called “unstable.”

Jackson was officially ruled out of Sunday’s AFC wild-card-round game against the Cincinnati Bengals after missing his sixth straight week of practice with what he called a PCL sprain. In a series of tweets Thursday, Jackson said he had suffered a Grade 2 sprain — moderate ligament damage and partial tearing — on Dec. 4 that was “on the borderline” of a Grade 3 sprain, which involves a complete ligament tear.

Harbaugh said after practice Friday that he hadn’t expected Jackson to tweet about his knee. Asked whether the Ravens agreed with Jackson’s assessment of his PCL injury, Harbaugh said that the “only person that can comment on that is the person.” He also declined to say whether Jackson, a pending free agent who hasn’t spoken publicly since his injury, had told him his knee was unstable.

“I’m not going to get into any conversations you have with players,” Harbaugh said. “That’s just not something that I would do. We have conversations about things all the time, and those are conversations between me and guys — whoever they are, really. That’s all I can say about it.”

In December, Harbaugh initially characterized Jackson’s injury as “not a season-ending type,” and later called his status “week-to-week.” But Jackson missed the Ravens’ final five games of the regular season and was seen limping in the locker room after practices and games. Tyler Huntley and undrafted rookie Anthony Brown have gone 2-3 as starters since Jackson’s injury, and the Ravens enter Sunday’s road game against AFC North champion Cincinnati as 8 1/2-point underdogs.

Harbaugh, who last Friday said he was “hopeful” Jackson would return for the playoffs, defended his optimistic outlook, saying it was “challenging” to offer accurate recovery timetables. He also did not rule out the possibility of Jackson returning later in the playoffs if the Ravens advance out of the wild-card round.

“You get asked questions about injuries all the time — and I understand it because it’s important — and you don’t always know,” he said Friday. “Sometimes you’re hopeful it will be quicker. I know I’m always hopeful that guys get back quicker, that it’s the front end of any kind of a prediction. Sometimes it goes the other way, and it’s longer, and you’re disappointed. That’s why it’s really tough to say.

“If I get up here and say it’s going to be a certain amount of time and it doesn’t turn out to be that time, and everybody’s like, ‘Well, you’re not being honest with us’ — it’s like, ‘No, you really don’t know.’ That’s how medicine works; you just don’t know, and I sure don’t know. There’s a range in there somewhere, and as a coach, you just try to get your guys ready and hope that the guys get back.”

The PCL, which is located at the back of the knee and helps stabilize the joint, is stronger and larger than the ACL. After the ligament is sprained, examined and assessed, “the most important thing is getting stabilization back to that joint,” said Naomi Price-Miller, a physical therapist with the University of Maryland Medical System.

Rehabilitating the muscles that support the joint, improving range of motion, limiting swelling and other techniques can be part of the recovery process. Grade 3 PCL sprains are the most severe type and require prompt medical attention, Price-Miller said.

Price-Miller, who is neither affiliated with the Ravens nor involved with Jackson’s treatment, said in a telephone interview Friday that a knee brace would offer Jackson’s knee support but is “not designed to strengthen the muscles.” Braces, she said, “help to really allow the patient to feel more stable, then maybe be able to proceed with further strengthening.”

Sports commentator Rich Eisen said on his radio show Wednesday that Harbaugh had told him, before the team’s loss to the Cleveland Browns in mid-December, that Jackson could’ve played with a knee brace — “but he doesn’t want to.”

Jackson, who has yet to agree to long-term contract with the Ravens and faces an offseason of uncertainty, said Thursday night that his knee was still inflamed, which Price-Miller said is the body’s natural response to injury. White blood cells, when activated, “help start the healing process,” Price-Miller said.

“The goal would be to expect [inflammation] and then start to work to decrease it,” she said. “I can’t make somebody’s inflammation completely go away. It’s going to happen, but as they’re doing exercise and strengthening and range-of-motion [workouts], it should begin to subside.”

Backup quarterback Tyler Huntley, a close friend of Jackson’s who could start Sunday, said that if Jackson “has a chance” to attend Sunday’s game, “I know he will.” But he couldn’t say for sure whether Jackson would be on hand at Paycor Stadium.

“I think he probably will,” he said, “but we’ll see.”

jonas.shaffer@thebaltimorebanner.com