RESUMEN
OBJECTIVE: To investigate whether risk factors related to pain vary at different stages of knee osteoarthritis (OA). METHODS: Individuals from the Osteoarthritis Initiative with available Kellgren/Lawrence (K/L) grade and numerical rating scale (NRS) data at baseline were included in this study. Pain severity was classified into 3 categories based on NRS scores: no pain, mild pain, and moderate/severe pain. Knee OA severity was stratified into 4 categories according to the K/L system. Pain risk factors were evaluated using generalized ordinal logistic regression analysis, and a heatmap was created to compare differences in standardized regression coefficients between subgroups of patients with different knee OA severities. RESULTS: A total of 4,446 subjects were included in this study: 1,574 individuals without pain (35.4%), 1,138 individuals with mild pain (25.6%), and 1,734 individuals with moderate/severe pain (39.0%). For the entire population and subjects in the premorbid-stage subgroup, knee injury history, diabetes mellitus, depression, use of nonsteroidal anti-inflammatory drugs (NSAIDs), and valgus malaligned knees were associated with more severe pain. Older age and stronger quadriceps muscles were associated with milder pain. As the disease progressed, the number of significant risk factors decreased. Only age and quadriceps muscle force remained significant in end-stage disease. CONCLUSION: Multiple factors are associated with pain in patients with knee OA. As the disease progresses, the number of significant risk factors gradually reduces. These findings suggest that strategies for managing pain related to knee OA should vary depending on radiographic grades.
