Comparing the association of widespread pain, multi-joint pain and low back pain with measures of pain sensitization and function in people with knee osteoarthritis.

To compare 1. measures of pain sensitization (PS) in people with widespread pain (WSP), multi-joint pain, low back pain (LBP) and knee osteoarthritis (KOA) only, in people with knee OA and 2. results of self-reported function and physical performance tests amongst these sub groups. Patients with knee OA consulting an orthopaedic surgeon were recruited from three Montreal area hospitals. A body homunculus was used to identify the presence of WSP (Y/N), multi-joint pain using a joint count (≥ 2 joints) and LBP (Y/N). Tests included pressure pain thresholds (PPT), temporal summation (TS), conditioned pain modulation and three physical performance tests. The Knee Injury and Osteoarthritis Outcome Score (KOOS) assessed self-reported function. Means were compared with Welch's ANOVA, post hoc tests and multiple regression analysis were performed. Two hundred twenty-one participants were evaluated (mean age: 63.4 ± 9.9 years, females n = 135 (61.1%)). Those with WSP significantly differed from those with LBP on PPT mean - 1.4, 95%CI (- 2.4, - 0.4), TS 10.3 (2.1, 18.5) and the stair climb test (SCT) 5.6 (1.3, 9.9). Those with WSP significantly differed from those with KOA only on TS 9.5 (1.0, 18.1), SCT 6.3 (2.0, 10.6) and KOOS - 14.2 (- 26.5, - 2.0). In patients with knee OA, those with WSP demonstrated greater degrees of PS compared with those with knee OA only, LBP and multi-joint pain. They also demonstrated a slower SCT compared with those with KOA only and LBP and decreased self-reported function compared with those with KOA only. These results should be confirmed in a longitudinal study.Key Points• In people with knee OA and widespread pain, measures of sensitization, self-reported function and physical performance were poorer compared with those with knee OA and LBP, knee OA and multi-joint pain or knee OA only.• Clinicians can consider these outcomes when planning management for these subgroups planning a comprehensive treatment program for this subgroup.