The relationship between knee pain characteristics and symptom state acceptability in people with knee osteoarthritis

Summary Objective To examine the association between osteoarthritis (OA) pain characteristics and symptom acceptability. Design Using a cross-sectional study design in a knee OA cohort we assessed socio-demographics, knee pain characteristics (Intermittent and Constant Osteoarthritis Pain (ICOAP); higher scores worse), frequency of intermittent pain ‘without warning' (unpredictable) or ‘after a trigger' (predictable) (never to very often) and the acceptability of knee pain symptoms (yes/no). Using logistic regression, we examined the relationship between pain characteristics and symptom acceptability. Results 136 cohort members' participated (mean age 74 years, SD 9.5; 54% female). Most (97%) reported intermittent pain (mean ICOAP intermittent score 36.8, SD 19.7) and 62 (46%) reported constant pain (mean ICOAP constant score 46.7, SD 20.2). Of those with intermittent pain, 42% reported frequent (often/very often) predictable pain and 27% frequent unpredictable pain. 35% reported "unacceptable" knee symptoms. In multivariable analysis, the odds of reporting an unacceptable symptom state increased with increasing intermittent knee pain scores and the effect was greater for those with vs without frequent unpredictable intermittent pain (adjusted OR per 10-point increase in ICOAP intermittent score 3.31, 95% confidence interval (CI) 1.38–7.97 vs 1.23, 95%CI 0.88–1.74, respectively; P value for the interaction = 0.03). Conclusion In a community cohort with symptomatic knee OA, both the severity and predictability of intermittent knee pain contributed to symptom state acceptability. Unpredictable intermittent knee pain was more likely to be associated with an unacceptable symptom state than predictable intermittent pain. Research is warranted to elucidate potentially modifiable determinants of unpredictable intermittent pain in people with knee OA.