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Published 7/1/2016
Emily Brook, BA; Emily Curry, BA; Elizabeth G. Matzkin, MD

Making the Distinction Between Sex and Gender

Which term should be used in research studies?
The number of published scientific articles examining male and female differences in orthopaedic medical conditions has increased during the past 25 years due to the National Institutes of Health Revitalization Act of 1993, which ensured the inclusion of women and minorities in clinical research. However, publications have inconsistently used the terms "sex" or "gender" to describe differences between males and females in research. The reason for such an inconsistency may be due to a lack of knowledge about the difference between the terms sex and gender.

This article aims to present the distinct definitions of both sex and gender and explain why medical researchers should use "sex" when discussing biologic etiology. In addition, this article seeks to evaluate the prevalence of sex versus gender terminology in AAOS Annual Meeting literature over the past 3 years to establish a consistency in terminology for future publications regarding male and female differences.

Why research male and female differences?
The passage of Title IX legislation in 1972 afforded female athletes the opportunity to competitively participate in all types of sports and across all levels of play. As a consequence, female participation in sports has increased exponentially during the past four decades.

The number of females coming to clinics with orthopaedic-related ailments has also increased. A recent study found that the proportion of sex-specific analyses in five high-impact orthopaedic journals increased from 19 percent of research articles in 2000 to 30 percent in 2010. Additionally, the 2001 Institute of Medicine (IOM) Report—Exploring the Biological Contributions to Human Health: Does Sex Matter?—highlighted the prevalence of pathologic functions that are indirectly or directly influenced by biologic differences between males and females. The report concluded by calling for the inclusion of sex differences in all aspects of scientific research.

Defining the terms
According to the IOM, sex is defined as "the classification of living things, generally as male or female according to their reproductive organs and functions assigned by the chromosomal complement." More generally, sex refers to the biologic differences between males and females driven by cellular processes. Every cell has a genetic chromosomal component of either XX (female), or XY (male).

The IOM defines gender as "a person's self-representation as a male or female, or how that person is responded to by social institutions on the basis of the individual's gender presentation." Gender is shaped by the environment and the experience of an individual. Gender represents an individual's choice to associate with either male or female qualities that are influenced by societal norms. Individuals can associate with a gender that is different than their biologic sex. Gender is not a biologic construct, rather it is a term constructed by society.

Correct usage in scientific research
Many researchers and orthopaedists may use the term gender due to the societal view that gender is the politically correct way to talk about differences between males and females. However, gender is not the correct term to use in orthopaedic research when discussing the biologic differences between males and females. Gender is an individual choice that does not necessarily reflect the person's biologic underpinnings.

The goal of assessing male and female differences in orthopaedic research is to examine the role that biologic factors play on the presentation, treatment, and outcomes of orthopaedic-related conditions. Therefore, sex is the appropriate term that should be used for orthopaedic research focusing on biologic differences between males and females. For example, a study examining the hormonal or anatomic differences of anterior cruciate ligament tears in male and female athletes should use the term sex because any disparities would be attributable to biologic differences between the sexes.

AAOS Annual Meeting Final Programs
We searched the AAOS Annual Meeting Final Programs for the years 2014 through 2016, including paper presentations, symposia, posters, and scientific exhibits. Instructional course lectures and orthopaedic video theaters were excluded. A search for the terms sex and gender was performed in the final programs for each year. Any paper presentation, symposia, poster, or scientific exhibit that mentioned the term sex or gender in the title or brief (often, one sentence-long) description of the research was included.

In the 2016 AAOS Annual Meeting Final Program, for example, of the 16 paper presentations, symposia, posters, and scientific exhibits that included the terms sex or gender in their titles or brief descriptions, 68.8 percent used the term gender to describe male or female differences, while 31.2 percent used the term sex. A search of the 2015 Annual Meeting Final Program found similar percentages (62.5 percent using the term gender, and 37.5 percent using the term sex). However, search results for the 2014 AAOS Annual Meeting Final Program showed the opposite finding. Of identified instances, 62.5 percent used the term sex while 37.5 percent used gender.

It should be noted, however, that a great deal more mentions of sex and gender occur in the Annual Meeting proceedings, which contain full research abstracts. For example, a search of the 2016 Annual Meeting proceedings reveals that the term gender appears more than 200 times, while the term sex appears more than 100 times.

Where do we go from here?
As authors and researchers, we encourage others to read the 2001 IOM report about the differences between sex and gender. Sex is the appropriate terminology to use when discussing biologic differences between males and females. The discussion about the difference between sex and gender should be continued in order to achieve accurate and consistent terminology in future publications.

Emily Brook is the research assistant for women's sports medicine in the Department of Orthopaedic Surgery at Brigham and Women's Hospital. Emily Curry, BA, is the senior research assistant for sports medicine and shoulder & elbow surgery in the Department of Orthopaedic Surgery at Boston Medical Center. Elizabeth G. Matzkin, MD, is surgical director of women's musculoskeletal health at Brigham and Women's Hospital, and a member of the AAOS Women's Health Issues Advisory Board. She can be reached at ematzkin@partners.org

Bottom Line

  • Sex is the biologic classification of living things as male or female according to their reproductive organs and functions assigned by the chromosomal complement.
  • Gender is a person's self-representation as a male or female or how that person is responded to by social institutions on the basis of the individual's gender presentation.
  • When discussing the biologic differences in orthopaedic conditions between males and females, researchers should use "sex" rather than "gender."


  1. Hettrich CM, Hammoud S, LaMont LE, et al. Sex-specific analysis of data in high-impact orthopaedic journals: how are we doing? Clin Orthop Relat Res. 2015;473(12):3700-4.
  2. Institute of Medicine. Exploring the biological contributions to human health: Does sex matter? Washington, DC. The National Academies Press; 2001. Available at http://www.nationalacademies.org/hmd/~/media/Files/Report%20Files/2003/Exploring-the-Biological-Contributions-to-Human-Health-Does-Sex-Matter/DoesSexMatter8pager.pdf Accessed June 26, 2016.
  3. National Coalition for Women and Girls in Education (NCWGE). Title IX at 40: Working to Ensure Gender Equity in Education. Washington, DC: NCWGE, 2012.
  4. Torgrimson BN, Minson CT. Sex and gender: what is the difference? J Appl Physiol. 2005;99:785-87.