Updated: Jul 15, 2021
Most of us who watch or participate in sports have experienced or heard of someone tearing their ACL. Most of us also know that this is a pretty big deal and that you will can be writing off sports and even walking normally for the months ahead.
This injury typically requires surgery to repair and involves a fairly lengthy rehabilitation process for return to athletics and/or a generally active lifestyle. So, why do some people tear their ACL and others do not? The ACL or anterior cruciate ligament, is one of four main stabilizers of the knee joint. It basically prevents your tibia or shin bone from sliding out from under your femur or thigh bone. Essentially, it allows the two bones to remain stacked on each other so that you can stand upright. When the ACL is torn, the most common symptom (besides pain) is a sense of buckling, or giving way of the affected knee.
Common causes of ACL tears are quick change of direction while running, jumping or landing, a blow (or tackle) to the knee with the foot being planted, or an hyper (over) extension of the knee joint under body weight.
All three of these scenarios can occur very often during sports or recreational activities and the numbers tell us that females are four to six times more likely to suffer an ACL rupture than males!
However, research tells us that preventing ACL tears is not just a matter of getting stronger muscles around the knee. How you move actually plays a huge role in how well protected your ACL is from injury.
A number of research studies looked at how well groups of athletes were able to control the position of their knee during a drop down landing test. They were asked to stand on a box and jump off landing on one leg.
The angle of how much the knee turned in was measured and then ACL injury rates were tracked throughout the athletes’ competitive seasons. This angle is called the knee abduction angle or KAM and looks like this:
Hewett TE, et al. Am J Sports Med. 2006;34,2:299-311
The collapse of the knee comes from the femur or thigh bone rotating in from the hip causing the knee to buckle inwardly. A 2015 study found that athletes that went on to tear their ACLs had 2.5 times larger KAM angles than those that did not have an ACL injury.
This means the injured athletes had a bigger degree of knee collapse inwardly than those that were not injured. This 2.5 times greater angle was calculated to be approximately 8 to 10 degrees larger in the injured athletes. This is not a large angle of motion, but it was found to be very significant in protecting the knee joint.
To check it out for yourself-stand in a mirror and squat down halfway on one leg and watch your knee. Be sure to check both legs. If you see your knee fall inward, you likely have some weakness at your glutes that may be putting you at risk for a knee injury.
You can work on strengthening these muscles with these glute exercises.
I also recommend an assessment by a physical therapist or movement professional to determine the steps you can take to improve your movement patterns and protect your ACL.
Don’t wait until you experience an injury before you take steps to protect yourself and your knee!
Stay Well & Feel Good,
*Always consult your physician before beginning any exercise program. This general information is not intended to diagnose any medical condition or to replace your healthcare professional. Consult with your healthcare professional to design an appropriate exercise prescription. If you experience any pain or difficulty with these exercises, stop and consult your healthcare provider.
Hi! I am Dr. Kim MacDonald. I am a physical therapist who specializes in empowering my patients to optimize how they move their bodies and improve their ability to do the things they love regardless of age, experience, or capabilities.
My experience in the health care field allows me to teach the tools you need to ensure that you are working safely to improve your pain and maximize your physical potential.
If you would like to know more about how you can help yourself be healthier and live a more active lifestyle, join me here.