Ravens quarterback Lamar Jackson said Thursday on Twitter that he was recovering from a borderline severe PCL strain in his left knee that has sidelined him for nearly six weeks and left the joint “unstable.”

Jackson, who hasn’t played or practiced since leaving a Dec. 4 win over the Denver Broncos, tweeted Thursday night that he had suffered a Grade 2 sprain — moderate ligament damage and partial tearing — that was “on the borderline” of a Grade 3 sprain, which involves complete ligament tears.

Jackson, who’s in the final year of his rookie contract, said his knee is still inflamed and “remains unstable.” He’s not expected to be activated for Sunday’s AFC wild-card-round game against the Cincinnati Bengals.

“I’m still in good spirits, as I continue with treatments on the road to recovery,” tweeted Jackson, who, in his first comments on the injury, did not offer a timetable for recovery. “I wish I could be out there with my guys more than anything but I can’t give a 100% of myself to my guys and fans.” He added: “I’m still hopeful we still have a chance.”

Coach John Harbaugh said after Jackson was hurt in Week 13 that the 2019 NFL Most Valuable Player was considered “week-to-week” and that the injury was not considered season-ending. After expressing hope Friday that Jackson would return for the playoffs, Harbaugh said Wednesday that he had “no updates at this time” on his playoff availability. Harbaugh’s scheduled to speak after practice Friday.

With Jackson sidelined and backup Tyler Huntley dealing with tendinitis in his right (throwing) shoulder, offensive coordinator Greg Roman on Thursday called the Ravens’ quarterback situation “very fluid ... and it probably will be up until game time.” Undrafted rookie Anthony Brown started in Sunday’s loss to the AFC North champion Bengals, who are 9 1/2-point favorites in Sunday’s rematch.

jonas.shaffer@thebaltimorebanner.com