Examining NaVorro Bowman’s lengthy recovery

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Before the 49ers’ loss to the Giants on Oct. 11, inside linebacker NaVorro Bowman met with NBC’s Cris Collinsworth and Al Michaels.

Not surprisingly, a topic of discussion was the horrific knee injury Bowman suffered 21 months earlier that sidelined him for the 2014 season.

“Wasn’t that amazing?” Collinsworth said on the air. “He talked about the piercing pain when he wakes up every morning. It takes him an hour to get that knee loose.”

Piercing pain? An hour to get the knee loose? Dr. Christina Allen, a clinical professor of orthopedic surgery at UCSF who was watching the game, raised her eyebrows. She was surprised to hear Bowman was still experiencing significant pain and stiffness nearly two years after his surgery.

“It is a little unusual at this point,” said Allen, who has served as an orthopedic team physician for the U.S. soccer national teams. “I was kind of surprised about how long it’s kind of taken him to get warmed up and get ready to go.”

Bowman, who tore the ACL and MCL in his left knee in the NFC Championship Game in January 2014, has made a largely successful return to the field this season. He has played 95 percent of the defensive snaps and ranks second in the NFL in tackles with 69.

However, he has struggled in pass coverage and has acknowledged he hasn’t recaptured his lateral quickness, which Allen said often takes two full years to get back.

In addition, Bowman, as he did with Collinsworth and Michaels, has noted how much maintenance his knee still requires. In late August, Bowman told Sports Illustrated that it takes him about two hours to get his knee ready for practice, although he later backed off that estimate when speaking with local reporters.

So why is Bowman, who declined to speak with reporters Friday, still experiencing such discomfort and stiffness? Allen offered several potential reasons, while noting she was speaking in general terms because she wasn’t privy to Bowman’s medical file.

Allen said issues can arise if a patient has surgery too soon after such an injury, which doesn’t allow enough time for the MCL to heal and can lead to arthrofibrosis. The condition can lead to dense scar tissue and is “pretty tough to beat even years down the line,” Allen said.

Bowman underwent surgery 16 days after his injury. Allen, who doesn’t know the severity of Bowman’s MCL tear, said a high-grade MCL injury can take six to eight weeks to heal.

“Sometimes when we try to get high-level athletes back, we push the envelope a little bit with doing the surgery and not waiting for the knee to get settled down,” Allen said. “And then people run into stiffness and scar-tissue issues after surgery. It’s always a fine line: How fast is too fast and how long should we wait? … That’s one thing that potentially could help explain why he’s having issues now.”

In addition, Bowman could have suffered more damage than two torn ligaments when his knee caved after Seattle wide receiver Jermaine Kearse crashed into the outside of it.

“If he had any other damage in his knee, like a cartilage injury, or meniscus injury,” Allen said. “Especially a cartilage injury. Cartilage loss can definitely give you a lot of pain and stiffness. There certainly could be more damage inside the knee that might be contributing.”

Head coach Jim Tomsula has repeatedly said he wants to limit Bowman’s snaps this season, although that’s yet to happen. Allen said Bowman could potentially experience less irritation, inflammation and stiffness with fewer exposures to trauma. Bowman hasn’t requested to leave a game, which isn’t surprising. On Friday, Tomsula was asked if he needs to begin removing Bowman from action to lessen his workload.

“Those are all conversations that he and I are having,” Tomsula said. “Obviously it’s well documented: The guy has worked his tail off to get back to the football field. He really wants to play football, and he really wants to be out there all the time and doing those things. When you have a competitive guy like that, that’s part of what makes him who he is.

“So, ultimately, that decision is mine. But I don’t think it’s that easy, personally. I think we need to work through this. I do believe, and I’ve expressed that with him, I want to make sure that we’re doing the best thing.”

Eric Branch is a San Francisco Chronicle staff writer. E-mail: ebranch@sfchronicle.com Twitter: @Eric_Branch