Beyond Bikini Medicine: Why Sex Differences Abound in MSK Disorders

Musculoskeletal (MSK) disorders don’t discriminate. They can impact anyone — and cause significant pain and disability, regardless of a person's biological sex. But as discussed in the previous blog in this series, research shows that people assigned female at birth (AFAB) face disproportionately higher risks of developing MSK conditions, experience greater pain and dysfunction, and are often dismissed or undertreated for their symptoms when compared to those assigned male at birth. It’s these differences that make sex-specific MSK care absolutely essential.

What exactly is driving these differences? We’re just beginning to find out. Longstanding sex and gender biases in medical research have left significant gaps in our knowledge of the pathophysiology and effective treatment options for MSK disorders for women compared to men. But as women’s health researchers continue to push for answers, we are gaining a new understanding of contributing factors, including those rooted in hormonal, anatomical, and biomechanical sex differences. Keep reading for an overview of what we’ve discovered so far.

Hormonal Factors in MSK Sex Differences

One of the biggest factors contributing to our sex differences is our sex hormones. Estrogen, progesterone, and testosterone impact our musculoskeletal system throughout the body and brain. These hormonal influences manifest across the lifespan:

• Puberty marks the onset of noticeable sex differences in skeletal development, with bones developing to be larger and thicker in males.
• Pregnancy and postpartum periods bring unique and significant MSK skeletal changes and challenges for women.
• Menopause, characterized by hormonal shift, is linked to increased rates of muscle and joint pain, impaired muscle regeneration, and increased rates of osteoporosis and osteoarthritis.

Estrogen, in particular, has protective effects on bone and cartilage health, while also influencing the structure and function of our muscles, tendons, and ligaments. Hormonal fluctuations during the menstrual cycle have been shown to impact MSK performance and injury risk.

Other Contributors to Sex Differences in MSK Disorders

Beyond our hormones, various biological differences contribute to MSK disparities between sexes, including the density of our bones, our muscle mass, and how our joints and ligaments function.

Anatomical & Structural Differences

Much beyond our genitalia, there are anatomical and structural sex differences throughout our bodies:

• Wider pelvis and increased pelvic tilt in females can lead to greater stress on the pelvis and lower back.
• Lower muscle mass and overall strength may contribute to increased joint loading and injury risk.
• Variations in joint laxity and ligament properties between sexes increase the risk of MSK injuries, particularly in the knee and shoulder.
• Differences in bone density can leave females more vulnerable to neck and low back pain.

Biomechanical Differences

Because of our anatomical and structural differences, we use our bodies differently:

• Differences in gait patterns, joint kinematics, and movement strategies may influence the loading and stress on musculoskeletal structures.
• These differences stem from anatomical variations as well as neuromuscular control and muscle activation patterns.

It’s important to note that while these biological and hormonal factors contribute significantly to the sex differences in MSK disorders, psychosocial, environmental, and occupational factors also play a significant role. A comprehensive understanding of these factors is crucial for developing effective, individualized prevention and treatment strategies.

Evidence-Based MSK Care is Sex-Specific

As researcher’s understanding of the hormonal, biomechanical, and anatomical reasons behind the sex differences in MSK health grows, it becomes more clear that the current one-size-fits-all approach to MSK is not inadequate. Women and folks assigned female at birth need MSK care through a sex-specific lens, including:

• Sex-specific screening and assessment protocols
• Tailored interventions and treatment options
• A multidisciplinary care team-approach that acknowledges every aspect of these unique differences

By recognizing and addressing these sex-specific factors, we can work toward more effective, personalized MSK for women and people AFAB, ultimately improving outcomes and quality of life.

Stay tuned for the next blog in this series, as we discuss how women and folks AFAB also experience MSK disorders differently — both physically and mentally.