Zion Williamson Is Back. Will His Knee Hold Up?

A 2017 study published in The American Journal of Sports Medicine examined 237 N.B.A. first-round draft picks from 2008 to 2015. It found that 43 percent of those who played a single sport during high school sustained a major injury in their pro careers, compared with 25 percent of those who played multiple sports. Multisport athletes also tended to have longer N.B.A. careers.

Dr. Brian Feeley, a sports medicine orthopedist in San Francisco who was a co-author of the study, said there was little evidence to indicate that, for a boy, specializing in a sport before reaching skeletal maturity around 16 or 17 would necessarily make him better. But such specialization is associated with higher injury rates.

The N.B.A. now recommends that players not begin specializing in basketball until age 14 or older; limit the scheduling of organized games; and rest at least one day a week and for a longer period each year.

“The question is whether somebody like Zion should have taken breaks,” said Dr. Feeley, who did not examine Williamson. Dr. Feeley added that a meniscus tear sustained by a teenager might suggest that young muscles and joints have been overloaded “when they’re not really ready for it yet” and a predisposition to types of injuries as a professional that “you may not necessarily experience until you were in your 50s or 60s.”

Griffin said the Pelicans were not “overly concerned” with the potential health effects of Williamson’s specialization as a youth, given his willingness to work to correct his biomechanical flaws.

Williamson expressed some frustration with his rehab and being unable to make his customary explosive moves. He said that, at times, he wanted to “punch a wall or kick chairs,” but he dismissed any concern over his decision to specialize in basketball since middle school.

“My advice would be, if you love the sport, just play it,” Williamson said.

The risk is real, though. Recent research, Dr. Jayanthi said, suggests that forceful, specialized training from a young age may contribute to biomechanical flaws. Such movement deficiencies have been widely studied by Dr. Marcus Elliott, a physician and founder of P3, a sports performance company that is completing a five-year study of nearly 500 current N.B.A. players.