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.