Your guide to a dreaded injury: The ACL tear

July 1, 2006

A tear to the anterior cruciate ligament is more common in children and adolescents than was once thought. Prompt, accurate diagnosis and referral can reduce long-term problems from this potentially devastating knee injury in a skeletally immature patient. First of two parts.

DR. RODENBERG is director of the sports medicine fellowship program at Grant Medical Center, Columbus, Ohio.

DR. CAYCE practices sports medicine at the Cincinnati (Ohio) SportsMedicine and Orthopaedic Center.

DR. HALL is a fellow in sports medicine at Grant Medical Center.

In an age of widespread participation in organized sports and increasing sports specialization among children and adolescents, it is rare to meet a young athlete or parent who is not aware of the potentially devastating effect that an anterior cruciate ligament (ACL) injury can have on an athletic career. Fear of an ACL tear in the skeletally immature athlete was long thought to be ill-founded because the epiphyseal growth plate of the tibial spine was believed to be weaker and more apt to give way than the ACL, making the young athlete more vulnerable to tibial spine avulsion injury than ACL injury.

One reason this misconception has persisted is the paucity of literature reporting epidemiologic studies of ACL tears in young people. Recent literature, however, supports the notion that mid-substance ACL injury (a tear to the middle of the ligament) in the skeletally immature athlete is more common than originally reported.

A retrospective analysis by Micheli and colleagues revealed that the frequency of ACL injury increased between 1992 and 1997 and that the increase correlated with growth in the level of participation in sports over the same period.1 When Shea and associates reviewed 8,215 insurance claims filed on behalf of youth soccer players, they found that 31% of knee injury claims for girls and 24% of such claims for boys were for an ACL injury.2 They also found claims for ACL injuries filed for girls as young as 12 years and boys as young as 5.2 years. Both Micheli's and Shea's reports note that ACL injury was more likely to occur in females than males (see "Why is ACL injury more common in female athletes than in males?").1,2

The increase in frequency of ACL injury in the skeletally immature athlete also may result from greater recognition by primary care physicians of history and examination findings consistent with ACL injury, increased use of magnetic resonance imaging (MRI), improved use of arthroscopy for diagnosis and treatment,3 and publicity given to high-profile, elite athletes who have sustained an ACL injury.

As with the epidemiology of ACL injury in skeletally immature athletes, few studies documenting the natural history of the ACL-deficient knee have been published until recently. Traditionally, nonoperative care has been standard. Failure to comply with activity modification dictated by this approach combined with functional instability places the young athlete at risk of recurrent injury. In fact, recent evidence suggests that the natural history of ACL insufficiency in children and adolescents parallels that of adults and is characterized by recurrent instability leading to subsequent meniscal tears and osteochondral injury despite rehabilitation and bracing.

Surgical reconstruction in children is complicated by the potential for physeal arrest. Optimal timing and choice of technique remain subjects of intense debate.2-5 As athletic participation intensifies, children face continued pressure from parents, coaches, peers, and themselves to return to play as quickly as possible after an ACL injury. The medical community is pushed to answer questions about treatment in ways that will return these young athletes to competition quickly and without sacrifice to future growth. This review provides a perspective that allows you to recognize a history consistent with ACL injury, support the diagnosis with a proper physical exam, understand the natural history of ACL injury, and appreciate the potential pitfalls of nonoperative and operative treatment. The first part of the article addresses diagnosis of ACL injury; the second, which will appear in the August 2006 issue, considers treatment, rehabilitation, and prevention.

Anatomy of the ACL