Doctors and coaches have noticed it themselves - more knee injuries, specifically tears of the ACL, the anterior cruciate ligament.
And now statistics show it's happening at a concerning rate.
According to a report in the journal "Pediatrics", the number of ACL tears in kids has gone up more than 2 percent each year, for the past 20 years.
And girls have a higher rate.
The doctors writing the report believe it's due to several factors, such as more girls playing sports.
But kids all-around are also playing with more intensity than 20 years ago, and they're specializing in one sport at an earlier age.
That means doing the same thing over and over year-round, and putting extra stress on some joints.
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Report: ACL tears in kids up 2.3% per year
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