Cracks in the Ranks Reveal the Hidden Cost of Military Service

New Study Shows Stress Fractures Expose the Toll of a Life in Uniform

June 17, 2026 by Sharon Holland

Stress fractures are a familiar challenge in military medicine-especially during the intense demands of basic training. But what happens after those first months of service? Do injury patterns change as servicemembers progress through their careers?

Researchers in the Department of Medicine at the Uniformed Services University (USU) and the Endocrinology Service at Walter Reed National Military Medical Center, set out to answer that question. Their recent study, "Stress Fractures in a U.S. Military Population by Duration of Active Duty-A Retrospective, Sex-Stratified Cross-Sectional Study," published June 9, 2026, in the journal Military Medicine, examined stress fractures not just in recruits, but across the full span of military service-from those in their first year to those with more than a decade of experience.

"Most prior studies have focused on recruits undergoing basic training, an environment where trainees are especially susceptible to stress fractures," according to Navy Cmdr. (Dr.) Andrew J. Spiro, lead author on the study. "Few studies have examined stress fractures in military populations with many years of service, or how fracture locations change after the initial basic training period."

Spiro's co-authors include Dr. Gregory S Schmidt, Dr. James H Prim, Dr. Nora L Watson, Dr. Mohamed K. M. Shakir, and Dr. Thanh D Hoang.

What they found challenges some long-held assumptions.

Using a retrospective review of active-duty service members in the National Capital Region, the authors analyzed 446 patients with a total of 537 stress fractures over a three-year period. Rather than focusing solely on incidence, they examined where these injuries occur-and how those patterns shift over time in a military career.

As expected, new recruits remain a high-risk group. But the type of injury they experience is notably different. Compared to their more experienced counterparts, new recruits had significantly higher percentages of stress fractures in the femoral neck, femoral shaft, and pelvis-injuries that are often more serious and potentially career-limiting.

At the same time, recruits had lower percentages of stress fractures in the foot, versus servicemembers later in their careers.

The authors also observed that nearly one in four recruits presented with multiple stress fractures-more than double the rate seen in more experienced personnel.

These differences matter clinically.

Hip and pelvic stress fractures can be more difficult to diagnose early and may carry greater consequences if missed. The findings suggest that providers should maintain a lower threshold for imaging new recruits who present with hip pain, as early detection may prevent progression to more serious injury.

"Even though the frequency of femoral neck stress fractures is lower than other types of stress fractures in new recruits, it makes up an outsized portion of recruits who are separated from training," Spiro says.

Why do these patterns exist? The answer is likely multifactorial.

New recruits face a sudden and dramatic increase in physical demands-greater intensity, frequency, and variety of load-bearing activity than they have previously experienced. This rapid transition may place unique stress on the hip and pelvis, particularly in individuals who are still adapting to military training.

Demographics also play a role. In this cohort, recruits were younger and included a higher proportion of female servicemembers-with female sex recognized as a known risk factor for stress fractures. However, even when male and female populations were analyzed separately, some differences persisted, suggesting that training-related and biomechanical factors also contribute.

Another important consideration is attrition. More severe injuries-such as femoral neck fractures-may lead to early separation from service. Over time, this may shape the population that remains, influencing the types of injuries seen later in a military career.

Interestingly, one finding remained consistent across all groups: the tibia was the most common site of stress fracture, regardless of career stage. This suggests that some injury mechanisms remain constant, even as others evolve.

For clinicians, these findings reinforce an important principle: military medicine must adapt to the full lifecycle of service.

Understanding how injury patterns change over time allows for more tailored prevention strategies, improved early diagnosis, and better protection of the long-term readiness of the force. What begins as a training injury can have lasting implications-not only for individual servicemembers, but for mission capability.

"Studies like this one are part of a broader effort to translate data into actionable insights," says Dr. Eric Elster, dean of USU's School of Medicine, "ensuring that the next generation of military physicians is equipped not only to treat injuries, but to anticipate and prevent them."