Orthopedic & Muscular System: Current Research
Open Access

Abstract

Risk of Osteonecrosis among Persons with Osteoarthritis of the Knee: Findings from the UK based General Practice Research Database

Susan Jick and Lin Li

Objective: To provide descriptive information on the risk of osteonecrosis (ON) in persons with osteoarthritis (OA) of the knee by age and gender.
Methods: The General Practice Research Database was used to construct a retrospective cohort of persons aged 18 to 89 years with OA of the knee between 1/1/2007 and 12/31/2009. Eligibility criteria included six months of medical history prior to the index date of knee OA and at least one activity record afterwards. Persons with a bilateral knee replacement prior to or on the index date were excluded. From this study sample we identified all firsttime diagnosed cases of ON in the study period and estimated rates.
Results: We identified 93,146 individuals representing 218,903 person-years (PY) who had a diagnosis of knee OA and who met all study criteria. The median time to onset of ON from the index diagnosis of knee OA was 17.4 months. The three-year cumulative incidence rate of ON in this knee OA population was 1.05 (95% CI: 0.68-1.55) per 10,000 PY. The risk of ON increased until age 85 years. The risk of ON was higher among females than males (females=1.31, 95% CI: 0.79-2.05 per 10,000 PY; males=0.67, 95% CI: 0.27-1.40 per 10,000 PY).
Conclusion: Rates of ON are higher in women and older people in the knee OA population which is predominantly elderly and female. With the growing population of elderly, especially females, the number of cases of ON is likely to increase among individuals with knee OA over time.