To determine the prevalence of joint-pain comorbidities in individuals with hip or knee osteoarthritis (OA) and to assess the differences in the characteristics of people with and without joint-pain comorbidities.
In this cross-sectional study, individuals referred to secondary care for treatment of hip/knee OA completed questionnaires to determine sociodemographic characteristics, disease-related outcomes, and joint-pain comorbidities. Joint-pain comorbidity was defined as pain perceived in a joint, other than the index joint, for more than half of the days in the preceding month. To compare differences in patient- and disease-related characteristics between participants with and without joint-pain comorbidities, we performed analyses of covariance and logistic regression.
A total of 401 individuals, 117 with hip OA and 284 with knee OA, returned the questionnaire (82% response rate); the mean ± SD age was 58 ± 13 years and 58% of the responders were women. Fifty-eight percent of the participants reported symptoms in ≥1 other joint. Participants with joint-pain comorbidities were more likely to be women, less educated, and have more medical comorbidities. Individuals with joint-pain comorbidities reported unfavorable outcomes on pain, functioning, fatigue, distress, and health-related quality of life compared with patients without joint-pain comorbidities (P < 0.001 for all). Moreover, use of nonsteroidal antiinflammatory drugs (P = 0.038), opioids (P = 0.010), and supplements (P = 0.019) was higher in the group with joint-pain comorbidities.
Our results indicate that individuals with joint-pain comorbidities represent a clinically relevant and large subgroup of people with OA of the knee or hip. We recommend addressing joint-pain comorbidities in both research and clinical practice.