Sixteen-year-old Lindsey Robinson already bears the scars from surgery to repair her anterior cruciate ligament, or ACL. It's one of the four major ligaments in the knee, helping to keep it stable.

"I couldn't feel the bottom half of my knee. It like freaked me out," says Robinson.

Lindsey was injured playing soccer. She's part of a growing number of young people in B.C. who are being sidelined by knee injuries.

"I think the participation of at risk sports has increased in B.C. and the Lower Mainland," says Dr. Chris Reilly, the head of orthopedics at B.C. Children's Hospital.

"I think the biggest issue is detecting kids with this injury," he says.

Reilly says if left undiagnosed, an ACL tear in children can increase the risk for future problems.

The ACL is the main ligament that stabilizes the knee and protects the cartilage. An injury can happen by simply twisting the knee, but many factors increase the risk for these injuries in children.

"They are also playing at a higher level, there is intense coaching, they play more frequently and they are involved in camps," says Reilly.

A player's speed, footwear and playing surface can play a role. Gender is also a factor: girls are at least four to six times more likely than boys to tear their ACL's during sport.

"We think it may have to do with their skeletal alignment - the relationship between their hips, their knees and their ankles - and how their legs are aligned," says Dr. Reilly.

Adults may have surgery to repair an ACL, but an operation for kids can be tricky. Still, it's becoming more common.

"There are growth plates around the knee that some of the surgical techniques cross so we carefully evaluate the patient's maturity, the growth remaining, and decide on an operative technique," says Reilly.

For teenagers, especially girls, the most common sport risking an ACL tear is soccer. Basketball also increases the risk because it involves a lot of planting the feet and pivoting.

For eight or nine-year-olds, skiing causes ACL injuries. It's important for parents to know that what may seem like a trivial knee injury may be much more.

The initial x-rays may appear normal, so if you have any doubt, have your child see their doctor in the weeks after the injury.

With a report from CTV British Columbia's Dr. Rhonda Low.