NEW ORLEANS — Pelicans star Zion Williamson's knee injury involves a torn meniscus, so what is that, and why can it take six to eight weeks to return to the court?

Let's start with a quick anatomy lesson. There's cartilage covering the end surfaces of the thigh and calf bones, then on top of that, are the menisci. They help with stability and act like a cushion to spread your body weight and force so it's not all concentrated on the cartilage.

Orthopedic surgeon Dr. Tim Finney, who did not treat Zion, showed us what normal menisci look like. They are nice and smooth, but a torn meniscus is jagged. And that's painful.

"What happens is the piece gets sort of irregular, where it flips back and forth in the joint, and that's where the pain comes from. If he tries to run, cut, that little piece of meniscus that's torn is getting caught between the two ends of the bone," explained Dr. Finney, an orthopedic surgeon with Southern Orthopaedic Specialists.

So, in about a 20-minute procedure under general anesthesia, the surgeon goes in a tiny portal and shaves down the rough edges and vacuums out any broken-off pieces.

"I would say that's probably the most common arthroscopic procedure done on the knee," Finney said.

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Finney says he sees this in teens, all the way to people in their 80s. After an arthroscopic routine debridement, patients can walk on it right away and start strengthening exercises. Because of post-op inflammation, however, the cartilage is softer, so running could damage it.

"He could possibly come back a little earlier than six weeks, but he's a big guy and because of his size, you may want to wait the extra week or two," Finney said.

Decades down the road, you could be a little more predisposed to arthritis, but without the procedure, arthritis can come faster. 

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His prognosis opinion for Williamson is good.

"I think he'll still be jumping out of the gym. Be able to do everything he needs to do," Finney said.

He also says if stitches are needed in the meniscus, you have to be on crutches for four weeks.

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