Preventing Knee Injuries in Women’s Sports

by Gypsy Bones, Boulder County Bombers

The knee is a beautiful thing. It is the joint between the two longest bones in the human body (the femur and the tibia), and bears the entire body’s weight. Normally a wonderfully functional class three lever, it is remarkably prone to injury.

The incidence of ACL injuries, and probably patellofemoral disorders such as pain, instability, and arthritis, are higher in female athletes than males. Women’s greater risk of knee injury plus more women participating in sports all the time (the number doubles each decade) makes the problem very widespread. Knee braces, both over-the-counter wraps and custom-made hinged braces, are a common sight in women’s sports.

For a great review of knee anatomy and injury, please see Papa Doc’s articles here and here. This article intends to follow up that information with a deeper look at why women are more prone to injury, and what can be done to prevent it.

Why are women more prone to injury?
Knee injury studies on female athletes have mostly been done on college soccer and basketball players in the U.S., and on team handball in Europe and netball in Australia. Interestingly, it is particularly non-contact injuries (caused by the athlete’s own body mechanics as opposed to an outside force) that are much more likely in women than in men. Also, as children, boys and girls have the same risk of knee injury; it is only after adolescence that the girls’ risk goes up.

A great article in Minnesota Medicine reviews what is known about the reasons for women’s knee injuries. It discusses the three categories of risk factors: anatomy, hormones, and neuromuscular mechanisms.

Much attention has been given to anatomic differences in the female knee, related to pelvic width, femoral angle, shape of bones and attachment of ligaments, but no direct link between anatomic alignment and injury has been found, though much has been speculated. Hormonal changes have been discussed as well, but again, no direct negative effect of estrogen on the ligaments themselves has been shown, though ligaments do have hormone receptors. Additionally, studies have set out to show a negative correlation between estrogen and ligament function, but whether testosterone conversely has a beneficial effect has been more assumed than demonstrated.

Neuromuscular mechanisms (meaning relating to the nerves and muscles, and the relationship between them) are the one modifiable risk factor for knee injury, and researchers studying many hours of video of athletes in action have shown some specific differences in the way we use our bodies that may be reasons for knee injury in women, and also some strategies to prevent those injuries.

When watching female athletes move, researchers noted that they tended to maintain more of an upright posture than males did when planting and pivoting. When the body is more upright, with less flexion at the hip and knee, the quadriceps has a mechanical advantage over the hamstrings. This gives the hamstrings less power to stabilize the knee. The hamstrings stabilize the knee by helping to hold the tibia close to the femur, thereby reducing the strain placed upon the ACL as it tries to do the same job. Conversely, quadriceps contraction during knee flexion actually increases the strain upon the ACL.
It was also noted that female athletes did not engage their buttock and core muscles as much as males did in order to rotate the leg. These muscles give a more central control to leg rotation. With less engagement of these muscles, riskier knee positions tended to be favored.

What is the cause of these differences in the way women and men use their bodies?
Boys often begin sports at a younger age, encouraging earlier development of running and jumping as well as hand-eye coordination and catching and throwing skills, all of which develop the neuromuscular system. Girls often miss this early exposure to motor learning.

Also, as boys grow, their muscle and bone growth keep up with each other. Girls’ bone development tends to be faster than the muscle growth so that for instance, the quads and hamstrings will be relatively smaller in proportion to the femur than a boy’s would be at the same phase of development. A study on knee injury in children showed that girls reach their maximum hamstrings strength at age 11.

Prevention strategies
The fact that many female knee injuries are non-contact injuries suggests that they may be due to predictable movement patterns that can be modified. Studies show that neuromuscular and educational interventions appear to reduce the incidence rate of ACL injuries by approximately 50%.

There are several groups that have developed great training programs and resources to reduce knee injuries in female athletes. One of these is the Santa Monica Sports Med Foundation PEP program (Prevent injury, Enhance Performance) It has been featured on Oprah and the Wall Street Journal. There is a clear and concise PDF on their website with diagrams of exercises, and you can even order a video. The PEP program includes warmup exercises, stretching, strengthening, plyometrics, and agility exercises. It is recommended for use three times a week, and the entire program takes 15-20 minutes to complete.

The Cincinnati SportsMedicine Research and Education Foundation developed a program called Sportsmetrics™ Warm-up for Injury Prevention and Performance program, or WIPP. They have an instructional DVD and manual available for $45. There is also a free poster available on their website, and they offer classes for certification.

Massachusetts General Hospital’s Sports Physical Therapy department came up with a sports conditioning and injury prevention program for the female knee as well. Their program consists of six progressive training stations which are detailed on their website. They also offer consultations, and they have a direct phone number listed to contact one of their therapists in case of any questions.

Applicable to derby?
Athletes in sports other than derby have obviously been the focus of injury studies and prevention programs. Are they applicable to derby as well? The Peninsula Rollergirls in San Francisco are using the PEP program, and discuss it on their website. And Iron Maiven from Los Angeles tore her ACL playing derby, and discussed it in an article on WebMD.

Logically it is evident that any repetitive movement such as skating can overdevelop some muscles around the knee, leaving others weaker. Cross training as well as injury prevention programs should be useful for addressing this potential imbalance.

We all know skaters that have suffered a knee injury and who have lost an entire season of play. Surgery is expensive and rehab can be slow, not to mention emotionally taxing. Injury also comes with a higher risk of re-injury. For younger athletes, potential scholarships or sports opportunities can be lost. It makes sense for us to do all we can do to protect our beautiful female athletic knees from injury and to keep ourselves on the track, the field, the trail, or wherever those amazing knees may take us.

Additional Resources:

http://ajs.sagepub.com/content/34/3/490.short

http://ajs.sagepub.com/content/early/2012/09/10/0363546512458227.full

http://www.ussoccer.com/news/coachesnet/2009/05/prevent-common-injuries-in-soccer-knee-injuries.aspx

http://www.sportsmd.com/SportsMD_Articles/id/418/cid/43/n/preventing_acl_injuries_and_anterior_knee_pain_in_female_athletes.aspx

http://girlscanjump.com/

http://ur.umich.edu/0001/Mar05_01/11.htm

http://www.acefitness.org/certifiednewsarticle/1043/when-it-comes-to-knee-injuries-are-women-really/

http://www.nismat.org/ptcor/female_knee

http://www.cdc.gov/media/pressrel/2008/r080725.htm

http://www.minnesotamedicine.com/PastIssues/PastIssues2007/June2007/Clinical-Arendt-June2007.aspx