Female participation in recreational, collegiate, and professional sports have more than quadrupled in the past four decades and the diversity of sports available for female athletes to participate in has consistently grown over the past century (Table 1). [1], [2], [3] This is as a successful result of several inclusion initiatives including Title IX in 1972 requiring equal opportunity in federally funded education programs (including athletic) and the International Olympic Committee goal for equal participation by the 2024 Paris Olympics (Table 2). [1,4] Sports such as women's gymnastics, basketball, volleyball, soccer, and tennis have become high profile events in the recent decade. These often require fast cutting, pivoting, and jumping/landing motions that place the knee at risk for injury. [5], [6], [7] However, investigation of injury risk and treatment for the female athlete remains significantly underrepresented in major orthopaedic sports medicine journals. [8] In addition to the growing number of female athletes, the types of sports in which women and girls participate has been changing as well, indicating a continued need for studies to better understand the needs in this evolving population. [9] Because of this, knowledge of the current approach to treat and prevent injuries in female athletes can be helpful to address the unique and specific needs of female athletes. [10]

Female athletes have been reported to be at greater risk of knee injuries when compared to male athletes (34% vs 22.5%). [7,11] Some of the known factors for increased risk for knee injuries include anatomic, hormonal, and training differences, although comparative studies are often limited due to male/female differences in sporting rules and equipment. Dynamic knee valgus kinematics, which consist of decreased hip flexion, decreased knee abduction, increased tibial internal rotation, and increase ankle pronation have been shown to predispose athletes to lower extremity injuries, particularly anterior cruciate ligament (ACL) injuries. [12] Female athletes have been reported to be more likely to have these neuromuscular risk factors. Wider hip to knee ratios increase the Q-angle while core strength influences anterior pelvic tilt, both of which contribute to dynamic valgus kinematics that have been associated with ACL injury and patellofemoral disorders. [13], [14], [15]

The potential effect of hormonal influences on injury risk has been investigated as a result of similar injury rates in prepubescent athletes as compared to a higher rate of knee injuries in postpubescent females. [16] Estrogen and relaxin can decrease the synthesis of collagen while progestin has the opposing effect. [17] Higher serum relaxin concentrations have been associated with higher risk of ACL injury in collegiate female athletes [18] and relaxin receptors on intraoperative ACL tissue of both males and females were found to have a higher affinity to bind substrate after being primed with estrogen. [19] Conversely, large-scale retrospective reviews of general population females taking oral contraceptives found a decreased incidence of re-rupture after ACL reconstruction, although current evidence in overall studies is low due to poor to fair levels of study quality. [20] Within contraceptive formulations, higher ratios of progestin to estrogen significantly increased the collagen expression in ACL tissue, decreased the expression of matrix metalloproteinases, and increased the maximum load before failure in rat models, indicating the need for future studies to differentiate effects based on hormonal balance. [17] While hormonal differences in female versus male athletes certainly exist, the role of hormonal homeostasis on injury risk and strong recommendations for specific clinical implications currently do not exist but continue to be investigated.