Annual Incidence of Knee Symptoms and Four Knee Osteoarthritis Outcomes in the Johnston County Osteoarthritis Project

Abstract

OBJECTIVE: To estimate annual incidence rates (IR) of knee symptoms and four knee OA outcomes (radiographic, symptomatic, severe radiographic and severe symptomatic) overall and stratified by socio-demographic characteristics and knee OA risk factors. METHODS: We analyzed baseline [1991-1997] and first follow-up [1999-2003] data (n=1,518) from Johnston County Osteoarthritis Project. Participants are black and white adults >/= 45 years living in Johnston County, North Carolina, US. Knee symptoms were pain, aching, or stiffness on most days in a knee. Radiographic OA was K-L grade >/= 2 (severe radiographic >/=3) in at least one knee. Symptomatic OA was symptoms in a radiographically affected knee; severe symptomatic OA was severe symptoms and severe radiographic OA. RESULTS: The median follow-up time was 5.5 years. Average annual IRs were: symptoms=6%, radiographic OA=3%, symptomatic OA=2%, severe radiographic OA=2%, and severe symptomatic OA=0.8%. Across outcomes, IRs were highest among those with the following baseline characteristics: age >/= 75 years; obese; a history of knee injury; or an annual household income </= $15,000. CONCLUSION: The annual onset of knee symptoms and four OA outcomes in Johnston County was high. This may preview the future of knee OA in the US and underscores the urgency of clinical and public health collaborations that reduce risk factors for, and manage the impact of, these outcomes. Inexpensive, convenient and proven strategies (e.g., physical activity, self-management education courses) complement clinical care, and can reduce pain and improve quality of life for people with arthritis. This article is protected by copyright. All rights reserved