Associations Between Pain Patterns and Self-Reported Clinical Outcomes in Patients with Knee Osteoarthritis

Objectives To study pain locations and patterns in knee osteoarthritis (OA) and determine associations between knee pain patterns and pain characteristics, functional status, and psychological status. Design A cross-sectional study. Setting and Subjects A convenience sample of 203 patients with knee OA was recruited from two university-affiliated hospitals from July 2016 to July 2017. Methods Pain locations were recorded with Photographic Knee Pain Map. Pain characteristics, functional dysfunction, pain catastrophizing, and pain self-efficacy were assessed, and demographic and radiographic data were also collected. Self-reported clinical outcomes across common pain patterns were compared. Results The medial joint line area (72.9%) was the most prevalent pain zone. The common pain patterns were diffuse (34.5%), isolated medial (22.7%), isolated anterior (9.9%), and medial-lateral pain (9.9%). Scores of intermittent pain (mean difference [MD] = 9.669, 95% confidence interval [CI] = 2.815 to 16.523) and knee-related function in daily living (MD =-10.353, 95% CI=-17.358 to -3.349) were worse in diffuse pain compared with isolated medial pain. Knee-related symptom scores were higher with isolated medial (MD=13.146, 95% CI=6.725 to 19.566), isolated anterior (MD=15.102, 95% CI=6.525 to 23.679), and medial-lateral (MD=15.281, 95% CI=6.704 to 23.857) pain relative to diffuse pain. Diffuse pain, after adjusting for confounding factors, was associated with more severe knee pain at rest, higher scores of constant and intermittent pain, lower knee-related function scores, higher pain catastrophizing, and lower pain self-efficacy scores (P<0.05). Conclusions The most common pattern is diffuse pain, which is associated with worse knee pain intensity at rest, constant and intermittent pain experiences, and worse physical and psychological status, compared with more localized patterns.