Why Are Knee Injuries Common in Female Athletes?

As the number of women participating in competitive athletics has dramatically risen over the past several decades, there has been a corresponding increase in the volume of female athletic injuries. This has led to an increased focus on the study of female athletic injuries and mounting evidence that there are distinct differences in the types, prevalence, and causes of sport injuries that men and women suffer.

One such difference is in the knees. Dr. Jennifer Baima, a former student athletic trainer at Notre Dame, a clinical instructor at Harvard Medical School, anda physiatrist who specializes in treating female sports injuries as head of the Women and Sports Medicine Program at Brigham and Women’s Hospital, discusses below why women are more at risk for knee injuries and what they can do to lessen that risk. Dr. Baima also describes this issue in her recent book, Biographies of Disease: Sports Injuries,as part of“an overview of the common injuries sustained by athletes of all ages and levels of competition.”

What are the anatomical factors that increase a woman’s risk of suffering certain sports-related knee injuries?

There are a variety of anatomical differences between men and women that could account for why women are much more likely to experience anterior joint pain or an anterior cruciate ligament (ACL) tear as a result of athletics.

Overall, a woman’s body is designed for flexibility and a man’s body is designed for strength. Correspondingly, a woman tends to have weaker quadriceps and hamstring muscles. This disparity places women at a disadvantage, as these muscles serve to help stabilize the knee and absorb shock when sharply cutting or jumping and landing during athletics.

However, recent research suggests that the difference between a man and a woman’s hip structure may be the most significant reason why women experience more knee injuries. A woman’s wider hips cause her to land in a more “knock-kneed” position – angled in from hip to knee and angled out from knee to ankle - to maintain balance, whereas a man’s legs tend to be straighter when he lands. This angular positioning of the legs produces a tremendous strain on the knees.

Are there any non-anatomical factors that could affect a woman’s risk of knee injury?

The failure to consume an adequate amount of calories is one non-anatomical factor that could substantially increase a woman’s risk of athletic injury. This lack of energy intake is part of the Female Athlete Triad, three interrelated female health issues – low energy availability, altered menstruation and osteoporosis – thought to be a significant contributor to a woman’s risk of athletic injuries. Low energy availability is caused by the tendency of female athletes to intake less calories than what would be desirable for their level of activity (sometimes exacerbated by or leading to eating disorders). This lack of energy availability can lead to a suppressed menstrual cycle and/or osteoporosis. A critical aspect of the Triad is that it begins with an issue that can be controlled – energy intake.

Are there particular sports that carry a greater risk for knee injuries in women?

Sports that require a great deal of cutting or jumping, such as basketball, soccer, or skiing, significantly heighten the risk of knee injuries in women. According to National Collegiate Athletic Association (NCAA) research, female basketball players are four times as likely to suffer from an ACL tear as male basketball players.

What can be done to reduce knee injuries in women?

One important thing that women can do to reduce their risk for injury is to avoid focusing entirely on one sport throughout the year. Switching sports from season to season gives specific body parts a better chance to recover.

Another strategy is to develop a training regimen that not only focuses on strengthening the quadriceps and hamstrings, but also teaches women to land with their knees facing forward (Figure 1), not inward (Figure 2).

Lastly, women need to focus on consuming a sufficient amount of calories. This will help to prevent athletic injuries and a multitude of other health issues.

Female Athlete Triad

What is the Female Athlete Triad?

The Female Athlete Triad refers to three interrelated female health issues – low energy availability, altered menstruation and osteoporosis. Low energy availability is caused by the tendency of female athletes to intake less calories than what would be desirable for their level of activity (sometimes exacerbated by or leading to eating disorders). This lack of energy availability can lead to a suppressed menstrual cycle and/or osteoporosis. The significance of the Triad is that it begins with an issue that can be controlled – energy intake. However, it is believed that the reasons for disparities go far beyond the Triad. Differences in hip and knee structure and function, as well as hormonal differences, are thought to increase the likelihood of certain injuries.

What are the risk factors for developing the Triad?

Anything that increases energy expenditure or reduces energy intake is considered to be a risk factor for developing the Triad. These factors include:

• prolonged exercise training to increase endurance or to promote weight loss
• dieting to lose weight or fat for participation in sports or other contests that demand a thin body
• decreased social eating
• perception that amenorrhea, excessive exercise, and extreme weight loss are normal for athletes

How can the Triad be prevented?

Prevention should start with educating young athletes about the importance of healthy eating throughout their lifetimes. Here is a sampling of healthy nutrition practices:

• bring snacks to practice and carry snacks around during the day
• eat foods containing protein and fat, such as nuts, cheese and yogurt, as well as carbohydrate-containing foods, such as cereal, crackers, pretzels, fruit and vegetables
• don’t skip meals
• never attempt to lose lean body mass
• choose friends and role models who also eat healthy and don’t assess their health solely on their appearance

Young female athletes should also keep track of the time in between their menstrual periods and report any abnormalities to their doctor.

What are some signs of the Triad?

Here are some things to look for as possible signs that someone is suffering from the effects of the Triad:

• actions – disordered eating, binging, induced vomiting, excessive use of laxatives and prolonged exercise
• physical signs - extreme weight loss, cold hands and feet, dry skin, hair loss, absent or irregular menstrual periods, increased rate of injury, delayed healing time for injuries and stress fractures
• emotional signs - mood swings, decreased ability to concentrate and depression

How is the Female Athlete Triad treated?

Treatment should address all possible causes of the Triad and should include medical, nutritional and psychological intervention.

Medical interventions include a physical exam and imaging for fracture assessment. Specific fracture treatment depends on the location in the body. Nutritional interventions include vitamin D and calcium supplementation. Psychological intervention may include evaluation and recommendations by a mental health care practitioner.

What are the consequences of the Triad?

Nutrient deficiencies and fluid/electrolyte imbalances can lead to impaired physical performance growth and mental functioning, as well as an increased risk of fractures and other injuries. Long-term consequences may include loss of reproductive function and serious, potentially fatal, medical conditions, such as dehydration and starvation.

Is it normal for female athletes to stop menstruating because of intense training?

No. It is never healthy, desirable or acceptable to stop menstruating before menopause. The termination of menstruation is a signal that a woman is not taking in enough calories to meet her needs. This is a particularly important issue for an athlete over the age of 16 who hasn’t started menstruating. Lack of menstruation at this age can inhibit normal pubertal growth and development.

Does the Triad lead to injuries that you don’t see as frequently in men?

Stress fractures, which are tiny breaks that occur when bone is weak, are much more prevalent in young female athletes than they are in young male athletes. This is caused by too much activity, not enough nutrients and/or a hormonal imbalance – i.e., one or more of the three components of the Female Athlete Triad.

Why has the volume and study of female athletic injuries increased so significantly in recent years?

The significant increase in the number of female athletic injuries over the past three decades can largely be traced back to the implementation of Title IX, a law requiring federally funded schools to provide equal athletic opportunities to male and female students, which has led to a dramatic rise in the number of women participating in intercollegiate athletics. Brigham and Women’s Hospital responded to this developing need by creating the Women and Sports Medicine Program – to care for female athletes of varying activity levels and ages.

Learn more

Visit the Women and Sports Medicine Web page or call us at 617-732-9300 for more information about the Women and Sports Medicine program at the Brigham and Women’s Hospital Orthopedic and Joint Disease Center.