When former McGill Martlet Volleyball player Charlotte Clarke went up for a hit during a match, she wasn’t too worried about how she was going to land. But when she came down on one leg, her teammates heard a crack.

“It was excruciating,” Clarke, U3 Arts, said. “The pain [made me want] to leave the earth for a little bit.”

Clarke had torn the anterior cruciate ligament (ACL) in her knee. ACL injuries are a serious problem for athletes and the general population, particularly among females. Surgery is usually required to repair the knee, using tissue from other parts of the body—such as the hamstring or patellar tendon—to replace the ruptured ligament.

“Close to a quarter of a million ACL injuries occur each year in Canada and the United States,” The Canadian Academy of Sport and Exercise Medicine reported in the 2014 issue of the Clinical Journal of Sports Medicine. “Female athletes in multidirectional sports have a four to eight times greater risk than male athletes of sustaining a noncontact ACL injury.”

According to the McGill Sport Medicine Clinic, anatomical differences are largely to blame. The ligaments in the knee intersect at a point called the intercondylar notch, which is narrower in women and causes the ligaments to cross at a sharper angle. Head Therapist and Manager Lynn Bookalam explains that the narrow ligament crisscross makes the ACL more susceptible to tears. A wider pelvis in females also leads to greater stress on knee ligaments. Additionally, females tend to have stronger quadriceps relative to their hamstrings. Males, by contrast, favor their hamstrings, which protects the ACL. A less researched theory is that female hormones affect the laxity of ligaments. When estrogen levels are high, ligaments are more “stretchy,” increasing the likelihood of an ACL tear. Finally, females tend to land from a jump with their legs more fully extended and their knees pointed in to a greater degree than males.

The ACL is one of the four main ligaments in the knee. Ligaments connect bone to bone; the ACL connects the tibia (shinbone) to the femur (thighbone). Bookalam says that ACL injuries occur when the femur goes in one direction and the tibia in the other.

Nicole Spadotto, U3 Arts and former Martlet hockey player, said that she remembers feeling a snap behind her knee when she tore her ACL. She was pushed off the puck, her skate got caught in the ice, and her knee twisted. She remembers her knee collapsing beneath her when she tried to get off the ice.

“My knee began swelling up immediately,” Spadotto said. “It was actually so swollen for a few weeks that the physios weren’t able to diagnose my injury.”

Despite the severity of the injury, sport spectators often don’t even realize an athlete is hurt. ACL tears can look quite harmless, as many of them are non-contact.

Assistant Professor Dr. Shawn Robbins of McGill’s School of Physical and Occupational Therapy said that non-contact ACL injuries are much more common than contact ones. Non-contact ACL injuries often occur when athletes are running, cutting, or landing. In fact, research has shown around 70 per cent of all ACL injuries result without direct contact. ACL injuries are generally associated with sports that involve a lot of cutting and changing direction—such as soccer, basketball, and football. Alexandra Lafrance, staff phyiotherapist at the McGill Sport Medicine Clinic, has found that most of her patients have been injured playing soccer.

Athletic trainers and physiotherapists at the McGill Sport Medicine Clinic see ACL injuries frequently. In the past year, Lafrance and her colleagues treated approximately 50 patients for ACL rehabilitation.

When the ACL tears or partially tears, the stability of the joint is severely diminished.

“Initially, there is a lot of swelling, the quadriceps muscles tend to not activate properly […] and mobility is greatly reduced,” Lafrance said.

She also stated that patients report instability in the knee following the initial injury. With physical therapy, however, this repercussion can heal within eight weeks. Athletes often find that, with physical therapy, just a few weeks after a tear, their knee feels significantly better—less swollen, more stable, and stronger.

Left untreated, an ACL injury will cause significant problems down the line. Every time the knee gives out, more damage is done to the bone and cartilage in the joint. Surgery is required to minimize additional injury.

“The decision to have surgery depends on a multitude of factors and will often be made by the orthopedic surgeon,” Lafrance said.

While some patients can resume full activity without surgery, that is not normally an option for serious athletes who want to return to high level competition. Even without surgery, patients must endure months of physical therapy to strengthen the muscles surrounding the knee and reduce the swelling of the joint. .

Still, according to Dr. Robbins, getting ACL surgery doesn’t affect the risk of joint degeneration and osteoarthritis. But, the early changes in the knee after an ACL tear–how the cartilage and bone are impacted by the trauma, as well as how the knee will now move differently–cannot be repaired with surgery.  

Even after her surgery, Spadotto said that her knee still cracks and gets stiff, and occasionally gives out on her.

“I didn’t want to become another statistic, but I can confidently say that it’s true that ACL injuries restrict athletic capacity,” Spadotto said.

It took Spadotto over 10 months to get her skills back to her pre-injury level.

Clarke went on to tear her left ACL as well as her meniscus playing volleyball roughly two years after her first surgery. She said that the recovery following the second surgery was a lot worse. “An ACL tear shakes you physically but more mentally because it’s a very traumatic event that puts you out of sports for a while,” Clarke said. “You’re sort of put in a cart-away category for athletes.”

Many athletes find the mental challenge surrounding the injury just as difficult to overcome as the physical one.

“As an athlete, to get the news that you’ve torn your ACL is completely devastating, which is what I would most like people unfamiliar with the injury to know,” Spadotto said.

Dr. Robbins said that making the running and cutting technique of an athlete sounder, as well as improving how they land, will significantly decrease the likelihood of an ACL tear. Strengthening the muscles surrounding the knee—especially the hamstring—is a good start. Sports federations, including FIFA, are focusing on promoting prevention programs to reduce injuries, especially among young or amateur players.

While surgery can often repair the ruptured ligament, Dr. Robbins emphasized the importance of muscle warm-ups  and proper technique as the best ways to avoid devastating knee problems.

A previous version of this article incorrectly stated Alexandra Lafrance's title as head athletic therapist. In fact, she is a staff physiotherapist at the McGill Sport Medicine Clinic.