ACL Tears in Young Athletes Soar

As youth sports get more competitive, the occurrence of season-ending ACL injuries continues to rise. Reconstruction risks include stunted growth among the youngest victims.

See also “How to Prevent Injury and Enhance Performance.”

Illustration by Chris McAllisterAs a sports medicine specialist, Dr. Bradley Smith is used to seeing patients limp into his office at Bryn Mawr Hospital. Shocking to Smith is how young some of them are.

“It certainly seems that there’s been an increase in ACL tears in young athletes,” he says.

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More than a decade ago, there were about 250,000 ACL injuries annually in the United States. That number has climbed yearly since, as has the frequency of tears among athletes 13 and younger. Bodies may be getting bigger, stronger and faster these days, but the ligaments retain the same strength regardless. “There are simply more kids getting active, but there are also kids playing more than one sport at a time,” Smith says. “When you have constant muscle fatigue, you get a little sloppy, you fall more easily, and you’re more likely to tear your ACL.”

It’s the reason tears happen later in games and seasons, and the reason there seems to be an MRI facility within a few miles of everyone’s house, he says.

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Though reconstructive surgery isn’t  medically necessary, it’s a typical route most athletes take to recovery—and the stakes can be high for young jocks.

The knee consists of a pivotal hinge joint that permits flexing and extension, plus slight inward and outward rotation. The ACL (anterior cruciate ligament) and the PCL (posterior cruciate ligament) inside the joint work with the surrounding MCL (medial collateral ligament) and LCL (lateral collateral ligament) to allow and restrict movement. The ACL connects the lower femur and the tibia. Tears can result from a hard tackle or non-contact pivoting. The latter accounts for about 70 percent of all ACL injuries.

“Because the ACL is inside the joint, it doesn’t get much blood flow, so a tear won’t heal on its own,” says Smith. “And when it tears, it completely tears.”

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A tear is similar to a frayed rope, and the shredded mess of fibers can’t be sutured to another piece of rope. Orthopedic surgeons like Bryn Mawr Hospital’s Dr. Kevin Freedman use either the patient’s own tissue or cadaver tendons to rebuild the damage, which typically involves drilling through the tibia and knee joint to secure the tendon grafts.

For kids, who have yet to reach musculoskeletal maturity, the issue of still-open growth plates poses a significant concern—especially for boys. “By age 14, some athletes have reached maturity. But, in general, this is not true for males,” says Freedman. “They’re not finished growing by that age, and we’re seeing more tears.”

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Found at the ends of long bones, growth plates are made of cartilage and are responsible for longitudinal growth. An injury to the growth plate during the drilling process could result in a shortened or malformed leg, the severity of which would depend on the amount of growing left for the patient.

Girls are at especially high risk for torn ACLs around their early teens, when they hit puberty. Female athletic participation has risen significantly in the past 30 years, but anatomical aspects play a role, too. Weaker core strength and the angle at which the knees are situated relative to the hip, compared to the narrower male pelvis, creates an increased chance of injury, especially when landing after a jump.

And females tend to be stronger in the quadriceps than the hamstring, creating a muscular imbalance, compounded by relatively weak abdominals.

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Medically speaking, a torn ACL doesn’t need to be mended in order for the knee to function. Walking, running and other types of forward motion are still possible. Side-to-side motion, though, could cause the knee to give out. In fact,  9- or 10-year-old athletes with ACL injuries might be advised to wait until their bodies can handle the procedure.

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“Our decision to do the surgery isn’t necessarily based on age,” says Freedman. “They have to have the maturity to be willing to give up sports for a time so their knee can heal. If they go back to sports too early and have instability in their leg, they could put the rest of the knee at risk for more damage.”

Smith and Freedman recommend training programs to strengthen muscles that protect against non-contact tears, pointing out that the factors that caused a tear in one knee can do the same to the other. ACL injury prevention programs are designed to alter neuromuscular responses in an effort to control landing and pivoting. This creates less stress on the ligaments, Freedman says.

And for those who think it’s all smooth sailing after surgery, Smith has news for them. “Successful rehab is just as important as a successful surgery,” he says. “It’s a long, slow process. But it’s just as important.”

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See page 5 for “How to Prevent Injury and Enhance Performance” …

How to Prevent Injury and Enhance Performance

Basic prevention components from the Santa Monica Sports Medicine Foundation (

Jog line-to-line on a soccer field, shuttle run, backward run (50 yards each)

Calves, quadriceps, hamstrings, inner thighs, hip flexors (30 seconds, two reps each)

Strength training
Walking lunges (two sets, 20 yards), Russian hamstring (three sets, 10 reps), single toe raises (30 reps each side)

Lateral and forward cone hops, single-leg cone hops, vertical jump, scissor jump (20 reps each)

Shuttle run, forward and backward (40 yards), diagonal run (40 yards), bounding run (40-50 yards)

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