Overuse injury of the physis: a "growing" problem.

Approximately 27 million children and adolescents between the age of 6 and 17 years participate regularly in team sports in the United States, and an untold several million more are involved in individual sports. Beyond the training and competition associated with the ‘‘seasonality’’ of a given sport, increasingly more youngsters are involved in ‘‘year-round’’ sport activity. Driven by the ever-increasing requirements for success in athletics, fuelled at times by parental dreams of collegiate scholarships, and captivated by visions of Olympic medals and professional contracts, many begin to specialize in a single sport at a young age. A focus on a single sport may lead to further intense training with personal coaches, fitness trainers, and attendance at sport-specific and position-specific training camps. Travel teams and club teams, usually with professional coaches and significant budgets funded with players’dues and other fees (no bake sales here! ), are well established in many communities and operate in addition to local community-based leagues or high school teams. It is not uncommon for a young athlete to compete on a community-based team (eg, American Youth Soccer Organization) and a club team during the same ‘‘season. ’’ As the race for collegiate athletic scholarships heats up in adolescence, some may choose to forgo playing for their high school to continue with a club program that may offer enhanced level and frequency of competition, more sophisticated coaching, and greater exposure to college coaches. Given this environment, it is no surprise that overuse injuries occur with great regularity. Although typical childhood injuries such as the common apophyseal injuries and patellofemoral pain are readily recognized and treated with little long-term sequelae, the bony growth plate, or physis, is a site of overuse injury that can easily be overlooked. Although their prevalence is not known, stress-related injuries involving the physis have been described in a multiplicity of sports including baseball, gymnastics, tennis, soccer, and distance running, among many others. The proximal humerus, distal radius, distal femur, and proximal tibia are the frequently reported sites of injury. Although extensive scientific data are not available, these injuries would seem to result from more prolonged repetitive loading, not from a simple increase in recent activity as might be seen in more commonly recognized overuse injuries. It is important to appreciate that, in some cases, stress injuries to the physis result in irreversible damage to bone growth. When diagnosed and treated with an appropriate period of rest, rehabilitation, and education, young athletes can successfully return to athletic activities—ideally in a way that will not result in further overuse injury to the still immature musculoskeletal system. Physeal stress injuries are thought to develop when repetitive loading of the extremity disrupts metaphyseal perfusion. This inhibits ossification of the chondrocytes in the zone of provisional calcification. Widening of the physis then develops as the chondrocytes continue to transition from the germinal layer to the proliferative zone, where they accumulate because they cannot calcify. This widening may be diffuse or limited to a focal area of cartilaginous extension into the metaphysis. Widening of the physis may be seen radiographically, whereas physeal cartilage extension has been best identified with magnetic resonance imaging. Most case series and cross-sectional data highlight the association of both training volume and intensity with physeal stress injuries. Basic science studies have