Background There is little data evaluating the risk for serious overuse injury in young athletes focusing on a single-sport or during growth spurts, in a clinical-based population.

Objective To determine whether sports specialization, weekly training volumes, and growth rates are associated with increased risk for injury and serious overuse injury in young athletes.

Design Case-control study.

Setting Injured young athletes ages (7–18yr) were recruited from sports medicine clinics and compared to healthy controls from primary care clinics presenting for sports physicals in 2 medical centers.

Participants There were 1206 participants (50.7% male) who were evaluated at baseline while longitudinal follow up data collection for up to 3 years is ongoing at time of submission.

Risk factor assessment Independent variables included hours/week of organized sports, free play, gym, sports specialization, and growth rate.

Main outcome measurements Dependent variables included total injuries, acute injuries, overuse injuries, and serious overuse injuries.

Results Injured athletes were older than uninjured athletes (14.1 +/−2.1 vs. 12.9 y/o +/−2.6, P<.001) and reported a higher avg. hrs/wk playing organized sports (11.3+/−6.9 vs. 9.4 +/−8.2 hr, P<.001). Picking a main sport to focus on one sport was an independent risk factor for injury even after adjusting for hrs/week in total sports activity and age (OR 1.48 P<.05). Young athletes participating in more sports hrs/wk than their age (P<.05) and participating in>2 times organized sports:free play were more likely to have a serious overuse injury (P=.001). Annual calculated growth rates did not impact injury status (4.76 vs 4.79 cm/yr,injured vs. uninjured respectively).

Conclusions Injured young athletes are older, spend more time in organized sports, and specialize. Our data support the need for counseling young specialized athletes as to the risks for overuse injury.