Although pain in knee osteoarthritis (OA) commonly affects activity engagement, the daily pain experience has not been fully characterized. Specifically, the nature and impact of pain flares is not well understood. This study characterized pain flares as defined by participants with knee OA. Pain flare occurrence and experience were measured over 7 days.
This was a multiple methods study; qualitative methods were dominant. Data were collected during the baseline portion of a randomized controlled trial. Participants met criteria for knee OA and had moderate to severe pain. They completed questionnaires and a 7-day home monitoring period that captured momentary symptom reports simultaneously with physical activity via accelerometry (n = 45). Participants also provided individual definitions of pain flare that were used throughout the home monitoring period to indicate whether a pain flare occurred.
Pain flares were described most often by quality (often sharp), followed by timing (seconds, minutes) and by antecedents and consequences. When asked if their definition of a flare agreed with a supplied definition, 49% of the sample reported only "somewhat," "a little," or "not at all." Using individual definitions, 78% experienced at least 1 daily pain flare over the home monitoring period; 24% had a flare on more than 50% of the monitored days.
Pain flares were common, fleeting, and often experienced in the context of activity engagement. Participants' views on what constitutes a pain flare differ from commonly accepted definitions. Pain flares are an understudied aspect of the knee OA pain experience and require further characterization.