Clinical Edge

Summaries of Must-Read Clinical Literature, Guidelines, and FDA Actions

Increase in Knee, Hip Arthroplasties Found in AS

J Rheumatol; ePub 2018 Jul; Ward

Rates of total hip arthroplasty (THA) in older patients with ankylosing spondylitis (AS) doubled over recent years, outpacing the increase in the general population, a recent study found. Rates of total knee arthroplasty (TKA) were also substantially higher in older patients with AS. Researchers used administrative data from 1999 to 2013 on Medicare beneficiaries to identify patients (aged <75 years) with AS and a comparison group without AS. Rates of primary THA and primary TKA were computed for each group, and standardized for age, sex, and race. 52,568 patients with AS and 4,617,179 patients without AS were analyzed. Researchers found:

  • Between 1999 and 2013, the standardized incidence of primary THA in patients with AS doubled from 4.5 per 1,000 patient-years (PY) to 9.6 per 1,000 PY.
  • Rates of primary TKA were higher in patients with AS than controls in all years.
  • In 2013, the standardized incidence of primary TKA in AS was 12.3 per 1,000 PY vs 5.7 per 1,000 PY in the comparison group.
  • Rates of primary TKA were twice as high among patients with AS and THA than among those without THA.


Ward MM. Increased rates of both knee and hip arthroplasties in older patients with ankylosing spondylitis. [Published online ahead of print July 1, 2018]. J Rheumatol. doi:10.3899/jrheum.171316.