Abstract
To examine whether knee subchondral cysts, measured on magnetic resonance imaging (MRI), are associated with incident knee osteoarthritis (OA) outcomes. We used longitudinal data from the Multicenter Osteoarthritis Study, a community-based cohort of subjects with risk factors for knee OA. Participants without a history of knee surgery and/or inflammatory arthritis (i.e., rheumatoid arthritis and gout) were followed up for 84 months for the following incident outcomes: 1) radiographic knee OA (Kellgren/Lawrence grade ≥2), 2) symptomatic radiographic knee OA (radiographic knee OA and frequent knee pain), and 3) frequent knee pain (with or without radiographic knee OA). In a subset of participants, subchondral cysts were scored on baseline MRIs of 1 knee. Multiple logistic regression, with adjustment for participant characteristics and other baseline knee MRI findings, was used to assess whether subchondral cysts were predictive of incident outcomes. Among the participants with knees eligible for analyses of outcomes over 84 months, incident radiographic knee OA occurred in 22.8% of knees with no baseline radiographic knee OA, symptomatic radiographic knee OA occurred in 17.0% of knees with no baseline symptomatic radiographic knee OA, and frequent knee pain (with or without radiographic knee OA) occurred in 28.8% of knees with no baseline radiographic knee OA and 43.7% of knees with baseline radiographic knee OA. With adjustment for age, sex, and body mass index, the presence of subchondral cysts was not associated with incident radiographic knee OA but was associated with increased odds of incident symptomatic radiographic knee OA (odds ratio 1.92 [95% confidence interval 1.16-3.19]) and increased odds of incident frequent knee pain in those who had radiographic knee OA at baseline (odds ratio 2.11 [95% confidence interval 0.87-5.12]). Stronger and significant associations were observed for outcomes based on consistent reports of frequent knee pain within ~1 month of the study visit. Subchondral cysts are likely to be a secondary phenomenon, rather than a primary trigger, of radiographic knee OA, and may predict symptoms in knees with existing disease.
Highlights
Osteoarthritis is the most common form of arthritis and is a leading cause of global disability, painful symptoms and a reduction in physical function[1]
Adjusting for age, sex and body mass index (BMI), the presence of subchondral cysts was not associated with incident radiographic knee OA (RKOA), but was associated with increased odds of incident symptomatic RKOA (OR: 1.92 and knee pain in those with baseline RKOA (2.11 (0.87 to 5.12)
Incident Symptomatic RKOA After adjusting for baseline age, BMI and sex, and using presence of subchondral cysts as our exposure, knees with evidence of subchondral cysts at baseline had increased odds of incident symptomatic RKOA compared to knees with no evidence of subchondral cysts
Summary
Osteoarthritis is the most common form of arthritis and is a leading cause of global disability, painful symptoms and a reduction in physical function[1]. Using a subsample of MOST, subchondral cysts were shown to occur in the absence of both MRI-assessed BMLs and cartilage loss in men and women with/at risk of knee OA[10]. Despite this evidence, most epidemiology studies concerning subchondral cysts are in the context of established knee OA. Subchondral cysts have been shown to influence the biomechanical properties of the subchondral bone by affecting bone mineral density[8] and by creating increased intra-osseous stress[17] Together, these mechanisms may thereby provide a potential path for the development of knee OA
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