The next time you twist or pivot to change directions, remember to thank your ACL.

“The ACL, or anterior cruciate ligament, is the primary stabilizer that gives support to the knee,” said Dr. Alexander Meininger, an orthopedic surgeon in Steamboat Springs and a member of the medical staff at UCHealth Yampa Valley Medical Center. “It connects the thighbone to the shinbone at the knee and prevents the two from shifting or rotating too much.”

Below, Meininger answers some frequently asked questions about the ACL.

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Do ACL tears happen more often in younger or older people? In more men or women?

ACL tears can happen in patients of all age groups. Tears are often a result of an athletic injury.

“They can happen at any time — downhill skiing, high school football or a slip and fall on the ice,” Meininger said.

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Females are more likely to tear their ACL than men.

“There are anatomical differences. Women tend to have a wider pelvis that puts knees at more of an angle, which can put the ACL under strain,” Meininger said. “The anatomy of the female femur is more narrow at the knee and may pinch or constrain the ligament.”

Hormonal cycles may also play a role. Women produce the hormone relaxin, which can cause tissue laxity or elongation during a woman’s menstrual cycle, and may make the ligament weaker.

Is there an activity that tends to produce more ACL tears?

While many may think ACL injuries are only from contact sports, the opposite is true.

“It’s more of a noncontact type of injury, where twisting or turning can cause ACL tears, not necessarily from a tackle or fall,” Meininger said. “The injury frequently happens when a foot is planted, and then the person abruptly pivots or changes direction, such as when someone on offense is trying to avoid someone on defense, as happens in soccer, basketball or football games.”

In the winter, the torque, or moment of force, that occurs during alpine skiing and snowboarding can also contribute to ACL injuries.

“There’s a lot of pressure on the knees during skiing,” said Meininger, a downhill skier and avid cyclist himself. “If you fall, and your ski is stuck in the snow, the force of rotation is applied through your knee causing it to twist and often resulting in a torn ACL.”

A backwards twisting fall getting off the chairlift is a common mechanism that can also forcefully strain the knee.

Will you know when you’ve torn your ACL?

“With any possible injury to the knee, ask yourself, ‘Do I trust my knee?’” Meininger said. “Some people may feel or hear a ‘pop’ when they fall, which can be an indication of an ACL injury. However, if you’re experiencing swelling, instability, wobbling or feel as though your knee may give way on you, it’s important to be evaluated.”

Is a reconstructed ACL as strong as the ACL a person is born with?

According to Meininger, an ACL graft is four times stronger than the ACL ligament you are born with.

There are two types of grafts. An autograft comes from the patient’s own body, whereas an allograft comes from a cadaveric donor. Autografts are most commonly taken from the patellar tendon or hamstring, with the quadriceps tendon being an option, as well.

“If a patient needs ACL reconstruction surgery, options are presented and together, we determine which is best for the patient,” Meininger said. “I tend to recommend using a graft from the quadriceps, as the average graft size is larger, and patients have fewer side effects.”

If you tear your ACL in one knee, are you more prone to tearing your ACL in the other knee?

Yes. There’s a 20% chance that patients who torn one ACL may sustain a tear in the other knee.

How can you prevent an ACL injury?

Preseason conditioning and exercises are paramount to teaching athletes how to safely jump, turn and land on their feet. Through video gait analysis, orthopedic surgeons and therapists can evaluate how someone lands on their feet. If the knee appears to cave in, the patient could be susceptible to an ACL tear.

“Taking care of your ACL is an investment of time, energy and commitment, whether you’ve had ACL reconstruction surgery or not,” Meininger said. “Strength training, improved balance, stretching, proper technique and warming up before exercise begins — all of these things contribute to a healthy ACL.”

Lindsey Reznicek is communications strategist at UCHealth Yampa Valley Medical Center. She can be reached at lindsey.reznicek@uchealth.org.