Abstract:

OBJECTIVES:To examine the relation of knee pain patterns to pain severity, and to radiographic osteoarthritis (OA) severity and duration. METHODS:The Multicenter Osteoarthritis Study is a longitudinal cohort of older adults with or at risk of knee OA. Participants' Intermittent and Constant OA Pain (ICOAP) scores were characterized as 1) no intermittent or constant pain; 2) intermittent pain only; 3) constant pain only; and 4) a combination of constant and intermittent pain. Knee pain severity was assessed using the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) pain subscale and the Visual Analog Scale (VAS). Radiographic knee OA (ROA) severity was defined as Kellgren Lawrence grade ≥ 2, and ROA duration was defined according to the clinic visit at which ROA was first noted. We assessed the relation of ICOAP pain patterns to knee pain severity, ROA severity, and ROA duration using regression models with generalized estimating equations. RESULTS:There were 2322 participants (mean age 68.8, BMI 31.0 kg/m2 , 60% female). Higher ICOAP pain patterns, i.e., a mix of constant and intermittent pain were associated with greater WOMAC pain severity compared with those without either pain pattern, OR 43.2 (95%CI 26.4-61.3). Results were similar for the VAS OR 71.2 (45.7-110.9). Those with more severe and longer duration of ROA were more likely to have a mix of constant and intermittent pain compared with those without either pain OR 3.7 (3.1- 4.6) and OR 2.9 (2.5-3.5), respectively. CONCLUSIONS:Knee pain patterns are associated with radiographic disease stage and duration, as well as pain severity, highlighting that pain patterns are important for understanding symptomatic disease progression.