While chronic joint pain surged across most of America over the past decade, South Dakota emerged as a puzzling exception—one that challenges researchers’ understanding of what drives arthritis-related suffering.
Between 2011 and 2021, South Dakota was one of only four states where joint pain prevalence actually decreased, along with Montana, Wyoming, and New York, according to research published in The Journal of Pain by University of Buffalo and University of Texas at Arlington teams.
Nationally, joint pain prevalence rose from 10.5 percent to 11.6 percent, adding 4.6 million Americans to the ranks of those suffering from moderate to severe arthritis-related pain, the study found.
What makes South Dakota’s success particularly mystifying is that it contradicts the study’s central finding about what prevents joint pain.
The research found that states with more generous Medicaid programs—measured by income eligibility, immigrant benefits, administrative burden, and benefit levels—had both lower joint pain prevalence and smaller gaps between educated and less-educated populations, according to Dr. Feinuo Sun, a University of Texas at Arlington assistant professor of kinesiology who led the research and spoke to the Associated Press in October 2025.
Yet South Dakota didn’t expand Medicaid during the entire study period, according to state records. Voters only approved expansion in November 2022, which didn’t take effect until July 2023—well after the research window closed.
During those critical years, South Dakota maintained some of the nation’s most restrictive Medicaid eligibility, with adults with two children needing to earn less than about $10,590 annually to qualify, while childless adults weren’t eligible regardless of income, according to the Center on Budget and Policy Priorities.
The state also faced other health challenges typically associated with higher pain rates. South Dakota’s adult obesity rate reached 30.3 percent—higher than the national average and increasing faster than most other states, according to a 2023 study published in South Dakota Medicine.
The predominantly rural state also struggles with geographic isolation and healthcare workforce shortages, according to America’s Health Rankings, factors that usually contribute to worse health outcomes.
So what explains South Dakota’s unexpected success?
Demographics may offer clues.
South Dakota experienced significant net in-migration during this period, with newcomers being substantially younger—median age 27 versus the state median of 38—and more educated, according to a presentation by state demographer Dr. Weiwei Zhang to the South Dakota Legislature. Between 2021 and 2022, South Dakota’s population grew at 1.52 percent, ranking fifth nationally behind only Florida, Idaho, South Carolina, and Texas, according to U.S. Census Bureau data analyzed by the Dakota Institute.
This influx of younger, healthier residents could have shifted the state’s overall health profile in ways that reduced joint pain prevalence across the population.
Still, the disconnect between South Dakota’s outcomes and the study’s findings about Medicaid presents a genuine puzzle for public health researchers. The study identified Colorado and North Dakota as particularly concerning, with both states showing sharp increases in both joint pain prevalence and educational disparities.
The South Dakota paradox suggests that factors beyond healthcare policy—perhaps including migration patterns, cultural practices, or other unmeasured policies—may play significant roles in population health outcomes. The state’s example also raises questions about whether the relationship between Medicaid generosity and joint pain is as straightforward as the data initially suggests.
For researchers, South Dakota represents an important case study: a state that achieved positive health outcomes despite lacking the policy interventions the study identifies as most effective. Understanding why could reshape approaches to addressing America’s growing chronic pain crisis.
