One in four people may develop symptomatic hip osteoarthritis in his or her lifetime

Abstract

Objective: To estimate the lifetime risk of symptomatic hip osteoarthritis (OA).

Design: We analyzed data from the Johnston County Osteoarthritis Project [a longitudinal population-based study of OA in North Carolina, United States (n=3068)]. The weighted baseline sample comprised 18% blacks and 54% women, and the mean age was 63 years (range=45-93). Symptomatic hip OA was defined as a Kellgren-Lawrence (K-L) radiographic score of ≥ 2 (anterior-posterior pelvis X-rays) and pain, aching or stiffness on most days, or groin pain, in the same hip. Lifetime risk, defined as the proportion who developed symptomatic hip OA in at least one hip by age 85, among people who live to age 85, was modeled using logistic regression with repeated measures (through generalized estimating equations).

Results: Lifetime risk of symptomatic hip OA was 25.3% [95% confidence interval (CI)=21.3-29.3]. Lifetime risk was similar by sex, race, highest educational attainment, and hip injury history. We studied lifetime risk by body mass index (BMI) in three forms: at age 18; at baseline and follow-up; and at age 18, baseline and follow-up and found no differences in estimates.

Conclusion: The burden of symptomatic hip OA is substantial with one in four people developing this condition by age 85. The similar race-specific estimates suggest that racial disparities in total hip replacements are not attributable to differences in disease occurrence. Despite increasing evidence that obesity predicts an increased risk of both hip OA and joint replacement, we found no association between BMI and lifetime risk.

Fig. 1

Study sample at baseline and first follow up * Baseline response rate=3068/5138=60%; clinic cooperation rate=3068/3690=83%. † Women aged < 50 years (i.e., reproductive age) did not have pelvic radiographs (n=312). † First follow-up sample comprised those who completed clinic examination and household interview (response rate=1590/2228=83%; clinic cooperation rate=1590/ 1739=91%). All women had hip radiographs at first follow up because they were aged ≥ 50 years.

Figure 2

Lifetime risk of symptomatic* hip OA in the JoCo OA. * Symptomatic was defined as either “pain, aching, or stiffness in at least one hip joint” or “pain in groin” in the radiographically affected hip. † Weighted to Johnston County population distribution in the 1990 United States Census. ‡ Stratified lifetime risk estimates may not sum to overall lifetime risk estimate because of missing data for stratification variables (Table 1). ** Education, BMI, and history of hip injury were time dependent (i.e., participants’ measurements at baseline and follow-up were analyzed). †† BMI at age 18 was calculated from self-reported height and weight. Baseline BMI was calculated from height and weight measurements at baseline clinical examination. ‡‡ History of hip injury in the symptomatic and radiographically affected joint.