OP0084 PRESSURE PAIN THRESHOLDS AND THE ASSOCIATIONS WITH CHRONIC WIDESPREAD PAIN, KNEE OSTEOARTHRITIS AND OBESITY IN INDIVIDUALS WITH KNEE PAIN

Abstract

Background:Approximate 30% of individuals with symptomatic knee osteoarthritis (OA) had developed chronic widespread pain (CWP) over a period of 20 years [1]. In order to prevent CWP in those with knee pain, it is important to study associated factors.Objectives:The aim was to study pressure pain thresholds among individuals with knee pain with or without radiographic changes, and associations with CWP, radiographic knee OA, and obesity.Methods:Out of 300 individuals with knee pain (with or without radiographic changes) from an ongoing longitudinal study, 279 conducted pressure pain thresholds (PPT) measurement at baseline in this cross-sectional study (71% women; mean age 51 years). The PPT were measured using a computerized pressure algometry on eight predefined tender points (Figure 1) out of the 18 points as part of the definition of fibromyalgia [2]. PPTs were dichotomised based on the lowest tertial vs the two higher tertials for each of the eight points. A group that had ≥4 points with low PPT (low PPT group) was compared to a group that had <4 low PPT (not low PPT group). A pain mannequin categorised the participants in three different pain groups: CWP, chronic regional pain (CRP), and no chronic pain (NCP) according to the definition of the ACR [2]. Radiographic knee OA was defined according to the Ahlbäck five grading scale as having score ≥1 vs score 0 [3]. Obesity was measured by bioimpedance measuring BMI and visceral fat area (VFA, cm2). To study associations, a crude logistic regression model controlled for age and sex was used including main and significant variablesFigure 1Differences in mean PPT in the eight tender pointsResults:The prevalence of CWP was 37% and higher in the low PPT group compared to those in the not low PPT group (Table 1). No differences were found between the groups in BMI, VFA or radiographic knee OA (Table 1). The low PPT group had significantly lower mean PPT on all eight tender points, was younger, had more pain sites, and more cases of fibromyalgia compared to the group with not low PPT (Table 1, Figure 1). Age (OR 0.95; 95% CI 0.92–0.97), having CWP (OR 3.00; CI 1.66–5.06), fibromyalgia (OR 21.91; CI 2.45–194.69) and increased number of pain sites (OR 1.13; CI 1.05–1.22) were associated with low PPT.Table 1.Descriptive statistics for the whole sample and for the groups: low PPT and not low PPTAlln = 279Low PPTn = 99Not low PPTn = 180p-valueAge, mean years (sd)51 (9)49 (9)53 (8)<0.001Women, n (%)197 (71%)69 (70%)128 (71%)0.804Pain group, n (%)<0.001 NCP/CRP160 (63%)41 (47%)119 (71%) CWP95 (37%)46 (53%)49 (29%)Numbers of pain sites, mean (sd)5 (4)6 (5)4 (3)0.003Fibromyalgia, n (%)8 (3%)7 (9%)1 (1%)0.001Knee OA Ahlbäck, n (%)59 (23%)16 (18%)43 (26%)0.132BMI, n (%)127 (48%)42 (47%)85 (48%)0.801 Normal Overweight/Obese139 (52%)48 (53%)91 (52%)VFA, mean cm2(sd)114 (54)115 (51)113 (55)0.788Conclusion:Baseline characteristics of individuals with knee pain showed a higher prevalence of CWP than in the general population [4]. In the group with low PPT, the prevalence was even higher. The study found associations between CWP and low PPT, however, almost half of the individuals with low PPT reported NCP/CRP. Moreover, a third in the group that not had low PPT reported CWP. The development of widespread pain in individuals with knee pain needs to be further studied over time to increase the knowledge of CWP’s origin in order to prevent the condition.