Weak ankles, blown-out knees, hip strain – you’d think this list of aches and pains would describe a middle-aged body.

Yet, increasingly these injuries are being seen in children.

While a moderate amount of physical activity is healthy and necessary for growing bodies, too much at a young age can cause harm, according to Mills-Peninsula sports medicine specialist Dirk Diefendorf, M.D.

The doctor, who serves as Serra High School’s team orthopedic surgeon, says he sees overuse and stress injuries in kids as young as 7 to 9 years old.

“I see kids on multiple soccer teams at one time – competitive teams, club teams, school teams. All year they are playing the same sport,” he says. “A lot of kids are having difficulty because their bodies are not being given time to rest, and they are still developing.”

Injuries becoming more common in children under 18 are repetitive strain and overuse injuries in the elbow, knee and shoulder, ligament injuries and growth plate injuries – where muscles and ligaments attach to the growing centers of long bones.

“I’ve seen severe injuries like an ACL tear in children as young as 9,” Dr. Diefendorf said.

How much is too much?

While inactivity is not the answer, it’s important for parents to remember that kids’ bodies need rest, both between matches and seasons.

Many injuries are caused by too much of one movement, such as throwing, which can lead to repetitive strain in young ligaments and muscles that can’t handle the stress, the doctor says.

“The parent often doesn’t realize, if their little leaguer pitches one day, then the next day plays catcher, they still do a lot of throwing,” he said. “They really aren’t getting the rest they need.”

Cross training in different sports can help prevent injuries and fatigue, too.

“A big problem we see is many kids in middle school and high school just focus on one sport. They do those things at the exclusion of other sports that use and develop different muscles,” Dr. Diefendorf says.

Tips for keeping kids injury free:

Warm up and cool down also applies to kids.

Stop at pain, a major warning symptom. Injuries and pain that persist longer than a couple weeks need to be evaluated by a sports medicine doctor.

Hydrate. Water and electrolytes are important before, during and after activities.

Rest. Make sure your child has downtime each week and between sport seasons.

Cross train. Add a little variety to your child’s activities to ensure a balanced body.