When junior Kristen Hennessey planted her leg to kick a soccer ball in the first day of tryouts last spring, she heard a noise she compared to “a piece of paper ripping.” As she felt her knee pop to the outside, she knew from past experience what just happened: a torn anterior cruciate ligament (ACL), one of the most dreaded injuries for any athlete.

One of the four major knee ligaments, the ACL functions by providing stability for the knee. The ligament attaches the knee to the femur, or thigh bone, and passes down the knee joint to the front of the upper tibia (shin bone). It is critical for stability, so many who suffer ACL injuries complain of the knee “giving out.”

Symptoms of an ACL tear include swelling of the knee joint and a feeling of instability which can occur with cutting and pivoting movements or even simply everyday walking. Many who suffer injury also hear a loud “pop,” which can sometimes even be heard by bystanders. Athletes who play sports that include high amounts of running and jumping, such as basketball, football, lacrosse, and soccer, are at the greatest risk for ACL injuries.

Females are also at a higher risk for injury, with recent studies showing girls eight times more likely to tear their ACL than men. This is due mostly to the fact that there is an increased angle formed by a woman’s hips and knees, putting the knee ligaments under more constant pressure.

Junior Gabby Hankinson was competing in a cheerleading competition last September when she came down on her knee during a jump and felt it pop out. It was a sharp pain at first, but then it went numb,” said Hankinson.

After rehabbing the injury for five days a week over nine months, she returned to cheer, only to suffer another tough injury this fall. I tore my meniscus and part of my ACL when we were practicing a new stunt for out routine. When I came out of the air to go back up, my knee snapped. It pretty much felt the same as last time, but it was like something was loose.”

Hennessey experienced the pain of an ACL tear twice, the first during a basketball game her freshman year and the second in the previously mentioned soccer tryout. “For both injuries, I was able to run four months after surgery. But the second time, I waited longer before returning to field hockey in the fall, it ended up being about a month longer. At four months, when I could run, it felt like I could do everything but my leg was still very weak.”

ACL injuries require strenuous rehab, generally after reconstructive surgery where the injured ligament is repaired and replaced with either a patellar tendon graft, hamstring graft, or allograft (from a cadaver).

“[The rehabilitation] strengthens the quadriceps and hamstring. [The length] depends on the surgeon and the patient but it can be anywhere from five months to a year,” said athletic trainer Kathy Ayers.

“For my first surgery, I had the hamstring graft but for the second they used a cadaver. I noticed that my leg was sorer from the first one because they had to take part of my hamstring,” said Hennessey.

Following surgery and successful rehabilitation, precautions are taken in order to attempt to prevent a second injury and to ensure that the injury is properly healed. “I have to wear a brace when I ever I do any lateral activity. The worst part was only being able to participate in some drills at field hockey practice and not being able to play in games for a month,” said Hennessey.

Any injury to the ACL is serious and requires proper evaluation and rehabilitation to return to prior level of play, and special care should be taken to enshelp prevent a second injury. “Even though my knee is better, it’s still always in the back of my mind whenever I do little things day to day involving jumping or pivoting,” said Hennessey.