Pain and quality of life in knee osteoarthritis, chronic low back pain and fibromyalgia: a comparative cross-sectional study

The objective of our study was to compare pain and health-related quality of life among patients with knee osteoarthritis (OA), chronic nonspecific low back pain (CNLBP) and fibromyalgia (FM). This cross-sectional study included 87 subjects, who were divided into three groups according to their diagnosis: knee OA (n=29), CNLBP (n=29) and FM (n=29), between March 2013 and March 2014. Pain intensity was measured using the Numeric Pain Rating Scale (NPRS), quality of pain using the McGill Pain Questionnaire (MPQ) and health-related quality of life using the 36-item Short-Form Health Survey (SF-36). Painful body areas were marked on a pain map. No statistically significant differences between groups were found for NPRS. Regarding MPQ, the knee OA group presented a lower pain-rating index in contrast to the CNLBP and FM groups, and no significant differences were found between the CNLBP and FM groups. A greater number of characteristic pain descriptors and painful locations were found in the FM group than in the CNLBP or knee OA groups. Regarding SF-36, the FM group presented statistically significant lower values for bodily pain in contrast to the knee OA group. Even though the global pain intensity was similar between groups, the findings suggest that the FM group presented the worst pain experience and a lower health-related quality of life than the knee OA group in terms of bodily pain. They also suggest that the pain experience was worse for the CNLBP group than for the knee OA group but health-related quality of life was similar.