When pro athletes tear an ACL, it's a significant injury, but major knee injuries aren't only suffered by professionals.

Experts at St. Joseph Regional Medical Center say major knee injuries are becoming increasingly common at the grassroots level.

"It's really surprising we see that at the younger levels. Especially with the high school athletes, we seem to be seing more and more of this," says orthopedic surgeon Dr. Anthony Scillia.

Athletes are used to seeing ACL injuries at the highest levels. A violent hit can do the trick, but even the slightest misstep can be damaging. Some blame artificial playing fields, others say professional athletes are too explosive. 

The injury doesn't only occur in football. Mariano Rivera tore his ACL shagging fly balls. Derek Rose did it with a jump stop in the lane. 

"I think athletes are training at a much higher level and with much higher techniques and are really getting to the point where these injuries happen more frequently," Scillia says.

Experts say technique is important, especially for girls, who are more likely to have an ACL injury because of bone structure in the legs.