Lonzo Ball’s knee pain remains a mystery. ‘Even the doctors are a little surprised,’ the Chicago Bulls point guard says.

As Lonzo Ball undergoes his second procedure Wednesday to address a lingering meniscus injury, the source of the pain sidelining the Chicago Bulls point guard remains a mystery.

Nearly nine months after Ball first injured his meniscus in a Jan. 14 game against the Golden State Warriors, Bulls medical specialists are still uncertain as to why Ball’s knee isn’t responding to surgery and rehabilitation. Ball hasn’t been able to run or play basketball since, remaining on the sidelines as the team opened training camp Tuesday in preparation for the 2022-23 season.

Knee pain hangs over Ball’s life, twinging every time he attempts to climb the stairs at home.

“It’s something that I’ve never dealt with,” Ball said. “Even the doctors are a little surprised about it. We’re all working together to figure this thing out.’’

Wednesday’s debridement procedure is another attempt to identify the source of the pain. Ball said the issue hasn’t been clear in MRI scans, so the surgery will allow doctors to analyze the area around his meniscus while removing debris such as cartilage and tissue.

The main concern is a limited range of mobility created by the pain. Ball said his knee loses strength whenever it bends between 30 and 60 degrees, inhibiting his ability to catch himself in motion or explode in a new direction.

He spent every day of the offseason with a specialist: trainers, Bulls medical staff, rehabilitation specialists in both Los Angeles and Chicago. Although Ball noticed small improvements over the summer, his mobility and power never improved enough to return to the court.

“There was a point where we would warm up and stuff and I would go through certain days and it would be fine,” Ball said. “But then whenever I got to real basketball activities, I just couldn’t do it.”

In the early days of the injury, Ball felt confident he would return by the playoffs.

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Knee injury recovery is familiar territory for Ball, who previously injured his meniscus while playing for the Los Angeles Lakers in 2018. The solution for that was simpler — removing part of his meniscus, followed by a standard rehabilitation period — and Ball made a quick and complete recovery.

But this process was completely different. The Bulls approached his recovery with urgency to attempt a return by the playoffs, but Ball couldn’t get over the hurdle of running without pain.

Nearly nine months later, he said the lack of information surrounding his injury adds to his frustration.

“I’m not going to say we (rushed the recovery) because I’ve torn my meniscus before and I came back and was fine,” Ball said. “I thought I was for sure going to be back for the playoffs. I think we all thought that was going to be the case.

“But something weird obviously happened. I’ve never felt pain like this, so it’s definitely a unique situation.”

At 24, Ball already faces questions about the longevity of his career, which has been defined by injuries: a sprained MCL, a torn ankle ligament and injuries to his adductor, knee, hip flexor, shoulder and thumb in four seasons with the Lakers and New Orleans Pelicans.

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Ball has yet to play more than 65% of a season, and that limited playing time dulls the shine of his pinpoint transition passes and tenacious defense.

“I’m not going to say I’m concerned about it, but obviously I wish I didn’t have to have any surgeries,” Ball said. “The plan this whole summer was to stay out of the surgery, but at this point this is all that’s left. So it’s something that has to be done.”

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For the Bulls, the more urgent question is when — and if — Ball will be ready to play this season.

He will return to Chicago after Wednesday’s procedure in Los Angeles to begin another rehabilitation attempt. The Bulls announced a recovery timeline of four to six weeks, but their predictions have yet to be accurate.

Executive vice president of basketball operations Artūras Karnišovas didn’t offer further insight into the Bulls’ hopes for Ball’s return during media day Monday, saying he doesn’t know how long Ball would require to ramp back up to speed whenever the pain subsides.

As Ball’s doctors continue to seek the cause of the pain, the Bulls face an increasing possibility of playing a full season without their starting point guard. But Ball said he can’t consider that possibility as he faces another surgery.

“That’s not in my mind right now, but that would be the worst-case scenario,” he said. “I know I can’t get back out there until I’m comfortable playing and can actually play. Whenever that day comes, that’s when I’ll have the jersey back on.”