Occurrence of radiographic osteoarthritis of the knee and hip among African Americans and whites: a population-based prospective cohort study.

Abstract

To compare the incidence and progression of radiographic osteoarthritis (OA) in the knee and hip among African Americans and whites. Using the joint as the unit of analysis, we analyzed data from the Johnston County Osteoarthritis Project, a population-based prospective cohort study in rural North Carolina. Baseline and followup assessments were 3-13 years apart. Assessments included standard knee and hip radiographs read for Kellgren/Lawrence (K/L) radiographic grade. Weighted analyses controlled for age, sex, body mass index, level of education, and baseline K/L grade; bootstrap methods adjusted for lack of independence between left and right joints. Time-to-event analysis was used to analyze the data. For radiographic knee OA, being African American had no association with incidence (adjusted hazard ratio [HRadj ] 0.80, 95% confidence interval [95% CI] 0.53-1.22), but had a positive association with progression (HRadj 1.67, 95% CI 1.05-2.67). For radiographic hip OA, African Americans had a significantly lower incidence (HRadj 0.44, 95% CI 0.27-0.71), whereas the association with progression was positive but nonsignificant (HRadj 1.46, 95% CI 0.53-4.01). In sensitivity analyses, the association with hip OA incidence was robust to a wide range of assumptions. African Americans are protected against incident hip OA, but may be more susceptible to progressive knee OA.