Objectives To study the prevalence of chronic widespread pain (CWP), chronic regional pain (CRP) and fibromyalgia (FM) and the association with measures of quality of life and function at 20 years follow-up in a population based cohort with chronic knee pain at inclusion with/without radiographic knee OA.
Methods 121 individuals (45% women, mean age (sd) 64 years (6) from a population based cohort study with chronic knee pain at inclusion, answered a questionnaire and had radiographic knee examination at 20 years follow-up. The responders were divided into three groups according to the reported pain duration and distribution - patients having no chronic pain (NCP), chronic widespread pain (CWP) and chronic regional pain (CRP). Pain and physical function was assessed by Knee injury and Osteoarthritis Outcome Score (KOOS, 0-100 worst to best). Health related quality of life (HRQL) was assessed by EQ-5D (0-1 worst to best) and Short form 36, a generic health utility questionnaire (SF36, 0-100, worst to best), which yields an 8-scale profile. Radiographic tibiofemoral osteoarthritis (TFOA) was defined as joint space width (JSW) <3mm and patellofemoral osteoarthritis (PFOA) as JSW <5mm. A multiple logistic regression analysis was performed to study the association with being in the worse half of EQ5D, SF36 and KOOS and pain groups at 20 years follow-up, respectively and controlled for age, gender and having or not having radiographic knee OA at 20 years follow-up.
Results Thirty percent reported CWP, 48% CRP, 22% NCP. Six percent reported that they had been diagnosed with FM. Of those with radiographic TFOA (n=18) 44% had CWP vs. 26% of the individuals with PFOA (n=32), 20% of those with TF and PFOA (n=5) and 27% of those without radiographic OA (n=52). Individuals reporting CWP had worse KOOS pain compared to NCP and CRP, (61.6 vs. 84.1 and 74.7, p<0.001 and p=0.005 respectively), more symptom (65.2 vs. 82.8 and 76.2, p=0.001 and p=0.012 respectively), worse ADL function (65.1 vs 87.4 and 79.1, p<0.001 and p=0.002 respectively), and worse KOOS QOL (46.5 vs 75.0 and 63.8, p<0.001 and p=0.004 respectively).
Individuals reporting NCP had better HRQL compared to both CRP and CWP (0.90 vs. 0.74 and 0.73, p<0.001 and p<0.001 respectively). Being in the worse half of EQ5D at 20 years follow-up was positively associated with CWP, OR 14.6 (95% CI 3.5-61.0), controlled for age, gender and radiographic knee OA. Similar associations were also found between seven of the subgroups of SF-36 (PF, RP, BP, GH, VT, SF, MH) and CWP, controlled for age, gender and radiographic knee OA. Being in the worse half of KOOS pain was associated to both CWP, OR 6.0 (95% CI 1.8-20.5), and having radiographic knee OA, OR 2.5 (95% CI 1.0-5.9), controlled for age and gender. Likewise being in the worse half of the other subgroups of KOOS (symptom, ADL, sport/rec and QOL) were associated to both CWP and radiographic knee OA.
Conclusions One third met the criteria for CWP. CWP was associated with patient reported pain, function and HRQL. Radiographic knee OA was associated with knee related outcomes assessed by KOOS and function but not to quality of life or health assessed by EQ5D and SF36. This suggest that it is important to assess CWP in the evaluation of patients with chronic knee pain with and without radiographic knee OA.
Disclosure of Interest None declared