Baseball shoulder, gymnast wrist, runner's knee. These are just a few of the labels sports medicine specialists use to describe the increasing number of repetitive-use injuries they see in young children.

April is National Youth Sports Safety Month and sports medicine experts at Johns Hopkins Children's Center would like to remind parents, coaches and pediatricians that fractures, sprains and concussions are not the only traumas they need to watch out for.

Unlike acute injuries, overuse injuries are more insidious and develop as a result of chronic strain or after a poorly healed old trauma, the Hopkins Children's experts say.

Amy Valasek, M.D., a pediatric sports medicine expert at Hopkins, says she sees an average of 100 children per month with sports injuries and at least half of the injuries she sees in clinic are caused by repetitive use.

The trend, the Hopkins Children's specialists believe, is fueled by a combination of factors, including more children specializing in one sport at a younger age, rigorous training regimens, resuming practice before an injury has healed completely and improper injury prevention.

Some 30 million to 45 million U.S. children between the ages of 6 and 18 participate in organized sports, many of whom are involved in specialized, intensive year-round training.

"If the current trend continues, in 30 years we'll have a crop of adults with serious chronic injuries that require surgery and aggressive treatment," Valasek says.

Symptoms of repetitive-use injuries include dull aches or pains in the affected area during and/or after activity with or without restricted motion and tenderness to touch. Any pain that lingers for more than three or four days should prompt a visit to the doctor, the experts say.

Children are prone to sport-specific trauma to the growth plates. For example, dancers, skaters and cheerleaders are vulnerable to ankle damage, while baseball and football players tend to injure their shoulders and elbows. Runners suffer shin pain and knee problems, while gymnasts are prone to wrist damage from repetitive weight bearing.

Their still-growing bones make young children and preteens more vulnerable to damage from overuse or repeated movements. The typical patient is one who plays multiple seasons of one sport rather than a variety of athletic activities. This is why, the experts advise, it's essential to avoid specialization in a single sport before age 14.

"The combination of repetitive use and skeletal immaturity puts these youngsters at high risk for injuries, some of them long-lasting, so it is really important that young children have whole-body conditioning and engage in a variety of athletic activities rather than one sport," Valasek says.

In addition to playing a variety of sports, Valasek recommends no more than five days per week of sport-specific training to allow the body to recover. Gentle warm-ups and whole-body stretches are critical before and after workouts. Taking time to reboot between seasons is also important, she says.

Importantly, Valasek says, pediatricians can play a pivotal role in prevention because they have a captive audience of both parents and children during the now-mandatory pre-participation physical exams.

While prevention is the best treatment, once an injury occurs, rest is critical. But this is a hard group to treat because of the pressure to forge ahead and compete despite pain rather than take time off to heal -- a Spartan ethic that can have negative effects on a child's growing body, Valasek says.

"It's important to remember that the main reason to engage children in sports is not to turn them into professional athletes, but to condition the whole body in a healthy way and instill a sense of discipline, responsibility and team work."