Lalli, now 39 and a resident of Canonsburg, Pa., is hobbled by knee pain. He gave up soccer. Then he had to give up running. He has tried swimming and cycling, but he said, “My heart is not in it.” Some days he can barely walk.
And he has no memory of any doctor warning him that he could get arthritis.
“It’s like a dirty little secret,” said Kocher, who is also the associate director of the division of sports medicine at Boston Children’s Hospital. “It’s not that anyone is covering up. It’s just that it’s not well known.”
But as someone who spends his days repairing torn knee ligaments in teenagers, he is worried. He has written a paper, soon to be published, that says the number of A.C.L. operations at 26 children’s hospitals in the United States has soared as more children and adolescents play sports that involve twisting the knee, like soccer and basketball, and often participate year-round.
In 2004, there were about 500 A.C.L. operations at those hospitals; in 2014, there were more than 2,500, he reports.
“This is a major issue for me,” said Kocher, who does more than 150 A.C.L. reconstructions a year, mostly in adolescents. “If a 15-year-old gets arthritis in 10 years, knee replacement is not a great option at age 25.”
One of the few long-term studies was done carried out by Britt Elin Oiestad, a physical therapy researcher at Oslo and Akershus University College of Applied Sciences, who followed 181 people for 10 to 15 years after A.C.L. surgery. Seventy-four percent developed arthritis that could be seen on X-rays. Some of those patients had yet to feel arthritic pain; 41 percent of those studied had reported knee pain that indicated arthritis.
“It’s scary,” Oiestad said.
While knee injuries have received the most attention in research on arthritis risk, other joints are not immune, said Dr. Brett Owens, a professor of orthopedic surgery at Brown University Alpert Medical School. People who repeatedly sprain an ankle are at risk, he said. And up to 40 percent of those who dislocate a shoulder get arthritis within about 15 years, he said.
What researchers want to know is this: Why do these injuries precipitate arthritis?
Is the answer a bone bruise that injures cartilage? Chemical changes that happen as the body tries to repair the injury? An intrinsic instability of the knee?
Research is not definitive but seems to support all of the hypotheses, as well as a strong hunch among investigators that there are genetic factors. Owens mentioned “A.C.L. families,” explaining, “I have operated on multiple siblings in a family.”
Doctors say they struggle with telling adolescents who just tore an A.C.L. that arthritis might follow. Owens says that he mentions arthritis but not in his initial conversations with young injured athletes.
“Most young athletes just want to focus on the problem at hand,” he said. “Yesterday in my office, I saw a 17-year-old soccer player. ‘Yes, you tore your A.C.L.’ The tears start to come. It is hard to talk to a 17-year-old about what their knee will be like in 20 years.”
Although Lalli, the former soccer player, said his arthritis diagnosis was a shock, he also said that knowing that it might happen would not have made much difference. He might have a genetic predisposition toward knee arthritis. His father took up soccer in his late 40s and had to have surgery at 50 when he tore the A.C.L. in his left knee.
Then he tore the meniscus — a piece of cartilage that acts as a cushion between the shinbone and the thighbone — in his right knee. He got arthritis later but thought it was because of his age, not his injuries.
Lalli’s arthritis progressed despite his receiving a second A.C.L. reconstruction that was more tailored to the anatomy of his knee. His initial operation had been done by a surgeon who did not position the new ligament in the exact place it had been before.
Lalli had the subsequent operation done by Dr. Freddie Fu, the chairman of the Department of Orthopedic Surgery at the University of Pittsburgh School of Medicine. Fu is a leader in A.C.L. operations that are more anatomically specific, and his procedure stabilized Lalli’s knee. Nonetheless, Lalli has faced years of disabling pain.
Four years ago, when his arthritis got so bad that he gave up playing soccer, Lalli asked for a knee replacement. Fu refused, telling him that artificial knees last only 10 or 15 years in younger and active people and that each knee replacement is more problematic than the one before.
A person can have only two or three knee replacements in a lifetime, Fu told Lalli, and so it was best to wait until he was 50.
Now Lalli is trying to decide whether to let his children play soccer. He has a 5-year-old and 3-year-old twins, and he said they “seem to naturally gravitate toward soccer.”
Lalli, who loves the sport, is torn and has been talking it over with his wife.
“I’m not sure what we will do,” he said.