Nov. 15, 2011 -- Ask Caleb Seymour, 8, of Holden, Maine, to name all the New England Patriot NFL players, and chances are he'll spout them out one by one. Caleb channels the players through his love of all things Patriots and all things football.
But perhaps nothing put Caleb more in sync with the football players than when he took a bad hit playing tackle football two months ago and tore his anterior crucial ligament, or ACL, the stabilizing ligament located in the knee. The same thing had happened to his hero, Patriots quarterback Tom Brady.
A stable ACL allows players to take powerful runs and make sharp cuts, kicks and pivots. But one wrong twist of the knee and an ACL tear can limit movement and push athletes to the sidelines, in some cases, for the rest of the season.
A torn ACL is usually surgically reconstructed by replacing the torn ACL with another tendon taken from the body. After surgery there can be stiffness in the knee, knee instability, and then there's a dreaded risk of infection, which Brady faced in 2008.
"Once you've torn your ACL, even if it's been reconstructed, there's a substantial risk of developing arthritis in the knee in 10 to 15 years," said Dr. Mininder Kocher, Caleb's specialist and pediatric orthopedist at Boston Children's Hospital.
An ACL tear is fairly common in professional and college level athletes, because of the intensity of the sports they play. It happened to Brady in the first quarter of the Patriots first game of the 2008 NFL season, when he threw a pass and his knee buckled as a defender struck him down.
But orthopedic specialists are now seeing a sharp rise in ACL injuries in elementary school children.
While the strength and force of impact of professional sports doesn't compare to kids' sports, mounting evidence suggests the intensity of children's sports is growing.
"We're seeing these injuries more frequently than we did before, and I think it's because the kids are just playing at a much higher, competitive level at younger and younger ages," said Kocher.
Almost gone are the days of free play -- backyard running, jumping, chasing one another around the playground, Kocher said.
"I always say I've never seen an ACL tear in a kid from playing kick the can," said Kocher.
Nearly 40 million children and adolescents play in organized youth sports in the U.S., according to the U.S. Centers for Disease Control and Prevention. Many play three to five times a week for several hours at a time.
"Kids are doing the same sports as their heroes, [but] unfortunately they're now getting the very same injuries as their heroes," said Dr. Theodore Ganley, sports medicine director at the Children's Hospital of Philadelphia.
At the Children's Hospital of Philadelphia, ACL tears in children under age 18 increased by 400 percent, from an average of 29 injuries a decade ago to 135 injuries in the last 3 years, according to findings presented at the American Academy of Pediatrics annual meeting in October 2011. Anecdotal evidence suggests that the trend of ACL injuries in kids is growing nationwide.
"These kids are having essentially adult style injuries with adult style consequences at a very early age," said Dr. Todd Lawrence, assistant professor of orthopedics at Children's Hospital of Philadelphia, and co-author of the study presented at the academy last month. "Because of their age and because of their growth, that injury and the implications of it are tremendous from all angles."
While Caleb's injury can be repaired, for many kids, such an injury can lead to long-term limited knee movement and uneven leg growth.
Because of the growing number of year-round sports, athletic programs should re-evaluate their training intensity levels, Lawrence said.
"We hope that what this research will highlight is the need for parents, coaches and the players to consider what they are doing in terms of their training and what sports, how much and at what level they want to participate," said Lawrence.
National campaigns, such as The American Orthopaedic Society for Sports Medicine program Sports Trauma and Overuse Prevention (STOP), and school programs have emerged to educate kids and their parents about how to play safely, and to become aware of the dangers of competitive sports.
For Caleb, who is currently the captain of his football team and who one day dreams of playing for the Patriots, the loneliness of sitting on the sidelines is almost as painful as the injury itself.
"I really, really want to play sports, but I can't," said Caleb.
In some ways, the injury has inched Caleb closer to his idol Tom Brady.
"I definitely think it's given him motivation," said Lisa Seymour, Caleb's mother. "When people ask him how does your knee feel, he always goes to, well, Tom Brady did it and he's still playing."
Both having suffered the same injury, Caleb wears his #12 jersey to all of his rehabilitation sessions – almost as good as having Brady there, he said.
That is, until "ABC's World News With Diane Sawyer" took the Seymour family to the Patriots' stomping grounds, Gillette Stadium, where they thought they'd just be getting a private tour of the grounds.
"So Tom Brady tore his ACL, and he plays sports," ABC News' chief health and medical editor Dr. Richard Besser said to Caleb as they stood at the center of the very same football field where Brady tore his ACL three years ago. "Do you know how he did that?"
"No," Caleb responded.
"Maybe you should ask him," Besser said, as Brady and his teammates Deion Branch and Wes Welker walked in to surprise Caleb and his family.
Caleb and Brady shared their sports stories. But more important, Brady shared advice on how to prevent future injury – advice that Caleb's doctors agree with.
Slow stretching and strengthening of the leg muscle, especially the front and back muscles of the thigh, can help rehabilitate the injured knee. Brady and Caleb have both been advised to avoid sports that include twisting and contact while recovering from their injury.
"There's no shortcuts to it. It's just a lot of hard work," said Brady. "You just got to put your mind to it, really try to go after it and hope that it gets really strong so you're back out there running with your friends."