To clarify the nature of the relation between hip fractures and osteoarthritis.
The study was a population based case-control study conducted in Sydney, Australia. Four hundred and sixteen men and women aged 65 years and over were recruited (209 cases, 207 controls). The presence of osteoarthritis was based on self reported pain, swelling, or stiffness of joints in the past year.
Among 189 subjects aged 65 to 79 years, but not in older subjects, there was an inverse relation between self reported arthritis in any joint(s) and risk of hip fracture: the age and gender adjusted odds ratio was 0.52 (95% confidence interval 0.27 to 0.98). The prevalence of self reported arthritis of the hip was much lower in patients with hip fracture (4%) than in controls randomly selected from the community (13%); the age and gender adjusted odds ratio was 0.33 (95% confidence interval 0.15 to 0.74). There was also an inverse association between the number of joints reported to be affected by arthritis and risk of hip fracture. These associations were not explained by differences between cases and controls in body mass index or physical activity.
The findings of this study support the hypothesis that there is a causal association between osteoarthritis and osteoporosis of the hip.