“She blew out her knee.”
If you’ve spent much time around women’s roller derby, you’ve heard these dreaded words. You’ve also seen injured players wearing knee braces, hobbling around on crutches or using a cane, and talking about surgery to repair their ACL or PCL. Unless you’re medically or anatomically savvy, you’ve probably been unsure about what these letters stand for but have surmised that whatever they are, you don’t want yours torn or busted. In fact, studies show that 50 to 100 percent of female athletes who do sustain these injuries will develop osteoarthritis in the knee within one to two decades.
Ryan Lowery MS ATC;L, a Certified Athletic Trainer and founder of the non-profit Derby Injury Prevention Network, said knee injuries are the most common injury he’s encountered while working with roller derby players.
Multiple studies show that female athletes who play sports involving jumping and pivoting are 4 to 10 times more likely than male athletes to tear their anterior cruciate ligament (ACL). In roller derby, injury to the posterior cruciate ligament (PCL) is also a notable risk due to hard falls onto the knee.
The ACL and PCL are two crisscrossing bands of tissue within the knee joint that connect the shin bone (tibia) to the thigh bone (femur). The ACL crosses in the front of the knee to prevent the shin bone from sliding too far forward on the thigh bone, and the PCL crosses in the back of the knee to prevent the shin bone from sliding too far back on the thigh bone. The PCL, which is considered the knee’s basic stabilizer, is almost twice as strong as the ACL, and provides an axis for the knee to rotate.
ACL injuries typically occur without contact during cutting, pivoting, and jumping, and are often accompanied by a popping sound. PCL injuries occur with sharp blows such as a knee striking the floor. Both ACL and PCL injuries can cause pain, swelling, stiffness, and knee instability.
Researchers who have investigated why female athletes are more prone to ACL injuries cite differences in anatomy, hormone levels, muscle strength and control, and mechanics during jumping and landing.
Lowery said that because women have wider hips than men, the female shin bone meets the thigh bone at a greater Q angle. He said that the wider a woman’s hips, the greater the Q angle is likely to be, which can produce a bit of a knock-kneed posture called genu valgum.
“This is significant because when an athlete lands from a jump, it’s important that the knee not cave inward but stays in line with the body,” he said. “When the knee caves inward, it oftentimes produces a rotational force that can tear the ACL and many times other structures in the process.”
In addition, the space within a woman’s knee joint is narrower, which can also increase the chance of the ACL being pinched or torn. Furthermore, while female hormone levels can confer injury prevention benefits by promoting flexibility, too much looseness can make it more difficult for the muscles around the knee to absorb force.
“Several studies also support the idea that females are also more prone to ACL tears during the pre-ovulation phase of their menstrual cycle (approximately days 9-14 of a 28 day cycle),” Lowery said. “Although the true cause is unknown, researchers speculate that it has to do with hormonal changes during the cycle which might increase laxity in the ligaments.”
According to the American Academy of Orthopaedic Surgeons, women’s ACL injuries are often caused by a lack of neuromuscular control in the hip and trunk. Video evidence shows that women sustain ACL injuries in the following ways:
- Lateral (side-to-side) trunk motion with the body weight shifted over one leg
- High knee abduction (knee turning inward)
- The plantar (bottom) surface of the foot fixed flat on the playing surface and away from the trunk
- Low knee flexion (knees not bent when landing)
“You prevent your knee from caving inward by strengthening the hip,” Lowery said. “The injurious rotation comes from the hip, not the knee. But strengthening all those other muscle groups has to go with it.”
Lowery said resistance training is paramount to preventing ACL injuries by building the hips, glutes, hamstrings, quadriceps, and core.
“Proper technique with skating, jumping, landing, and athletic positions also help a lot,” he said.
Lowery added that many derby athletes think they are in a good, low athletic position when they are actually bending their backs or using some other sort of pattern of compensation in place of leg strength.
The Sports Therapy Department at the Massachusetts General Hospital has created a sports conditioning and injury prevention program for the female knee that emphasizes increasing agility by building muscular strength and control in the legs and core. Some exercises included in the program are lunges and abdominal crunches; forward, backward, and diagonal running; and forward, backward, and side-to-side hopping on one or both feet. The entire training program can be accessed here: http://www.massgeneral.org/ortho/services/sports/pdfs/conditioning-female-knee.pdf
Lowery recommends performing these types of exercises 2-3 times per week.
In addition, the program emphasizes proper jumping techniques such as landing on the balls of the feet with the knees slightly bent.
“Especially when landing, land very softly and absorb the shock of your weight using your ankles, knees, hips and maintain a solid core,” Lowery said. “Watch yourself in the mirror.”
In terms of PCL injuries, Lowery admits that they are harder to prevent.
PCL injuries during roller derby can occur from inadequate protection when knee pads slip down the shin during a fall. Choosing properly fitting pads with a lot of cushioning can lessen the impact from a blow to the knee. Custom knee braces are also an option, but they come with a hefty price tag.
“The only way to prevent a PCL injury is to not fall on the knee, which means refraining from play—yeah, right!—or having an increased situational awareness,” Lowery said. “Strong quadriceps might help, but a great enough force can always overcome strong muscle.”
For more information on how to prevent roller derby injuries, check out the Derby Injury Prevention Network on Facebook (https://www.facebook.com/DerbyIPN).