Basic Science Tip #513

Relative Energy Deficiency In Sports

In a recent AAOS instructional course Dr. Karen Sutton explained the concept of “relative energy deficiency in sports,” or RED-S (1). This may occur in male or female athletes. In females the concern is altered reproductive hormones and lower BMD. The female athlete triad is defined as low energy availability, menstrual dysfunction, and low bone mineral density (BMD) (1). One focus is the identification of female athletes at risk for stress fracture or the identification of the female athlete triad in a female presenting with a stress fracture. However, there are many athletic injuries affected by this triad making important to the orthopaedics clinician.

There are a number of factors entering into the rate of anterior crucial ligament injuries in females (2). Biomechanics, training and metabolic factors may account for the double incidence of ACL injury in non-contact sports. In addition to specific training and surgical intervention, prevention rest on understanding the triad in any female athlete being evaluated for sports. This is highlighted in a current sports medicine report by the American College of Sports Medicine. Amongst other factors contributing to symptomatic patellofemoral dysfunction is muscle weakness and/or imbalance. Additionally inflexibility in the pelvic femoral region and around the knee play a role. There is a far higher incidence of stress fracture in female. A key factor is low energy availability, poor nutrition, menstrual dysfunction, low and/or poor bone mineral density, low body mass index (BMI), low body weight (adolescents) and disordered eating/eating disorders.

High on the list of disproportionate injuries in female versus male athletes are stress fractures (3). The effect of the female athletic triad stands paramount. In unconditioned individuals with no history of significant stress loads repetitive loads over short periods of time may lead to bone micro-damage that leads to cortical resorption and, ultimately, fracture. In an investigation of stress fractures in female athletes the female athlete triad was found to be an especially important factor. All physicians and other practitioners in sports medicine have been alerted to the development of newer grading schemas using MRI and radiographic findings to intervene before fracture occurs. However, screening for at-risk athletes is the prime directive for all to prevent stress fractures.


2. [No authors listed] Female Athlete Issues for the Team Physician: A Consensus Statement-2017 Update. Curr Sports Med Rep. 2018 May;17(5):163-171.

3. Abbott A, Bird M, Brown SM, Wild E, Stewart G, Mulcahey MK. Part II: presentation, diagnosis, classification, treatment, and prevention of stress fractures in female athletes. Phys Sportsmed. 2019 Jul 11:1-8.