To study the prevalence of chronic widespread pain (CWP) and chronic regional pain (CRP), and their association to quality of life, pain, physical function at a 20-year follow-up in a population based cohort with chronic knee pain at inclusion.
121 individuals (45% women, mean age 64 years, range 54-73) with chronic knee pain from a population-based cohort study, answered a questionnaire and had radiographic knee examination at a 20-year follow-up. The responders were divided into three groups according to reported pain; individuals having no chronic pain (NCP), chronic widespread pain (CWP) and chronic regional pain (CRP). Pain and physical function were assessed using Knee injury and Osteoarthritis Outcome Score (KOOS). Health related quality of life (HRQL) was assessed with Euroqol-5D-3 L (EQ5D) and Short form 36 (SF36). The associations between pain groups and KOOS, EQ5D, and SF36 were analysed by multiple logistic regression, controlled for age, gender and radiographic changes indicating knee osteoarthritis (OA).
The prevalence of CWP was 30%, and CWP was associated to worse scores in all KOOS subscales, controlled for age, gender and radiographic changes. CWP was also associated to worse scores in EQ-5D and in seven of the SF-36 subgroups, controlled for age, gender and radiographic changes.
One third of individuals with chronic knee pain met the criteria for CWP. CWP was associated with patient reported pain, function and HRQL. This suggest that it is important to assess CWP in the evaluation of patients with chronic knee pain, with and without radiographic knee OA.