Understanding the Pain Experience in Hip and Knee OA

PURPOSE: Focus groups were conducted in Canada, Australia, the US and England to examine the pain experience of people with hip and knee OA, focusing on changes over time and most distressing features.
METHODS: Participants were English-speaking, aged 40+ years with painful, x-ray confirmed hip or knee OA. Those with recent joint injury or replacement, or other chronic pain disorders were excluded. Focus groups obtained detailed descriptions of OA pain from early to late disease. A modified Patient Generated Index (PGI) was used to assess participants’ OA pain concerns. The PGI requires participants to: a) identify up to 5 distressing pain features; b) rate their level of distress for each item (from 0 to 6); and c) “spend” 10 points to buy relief from their distress, assigning more points to items deemed most important. Sociodemographics and arthritis severity were assessed. Focus groups were audio-taped, transcribed verbatim and data entered into N6. Transcripts were reviewed independently by ≥ 2 researchers to identify distinct themes. Themes were compared and consensus reached. Content analysis was performed to examine patterns of responses by subgroups and from early to late disease. Descriptive statistics were used to summarize PGI responses overall and by subgroups of interest.
RESULTS: 36 hip and knee focus groups were conducted in 143 participants (52 hip OA; 91 knee OA). Participants’ mean age was 69.5 years (47-92 years); 62.0% were female, 93.7% Caucasian, and 17.0% had ≤ high school education. Mean WOMAC pain score was 7.7/20 (0-17). Participants clearly described two distinct types of pain as their OA progressed - a dull, aching pain, which became more constant over time, punctuated increasingly with short episodes of a more intense, often unpredictable, emotionally draining pain. The latter, but not the former, resulted in significant avoidance of social and recreational activities. Compared with knee participants, those with hip OA described a more rapid progression and used ‘intense’ descriptors (e.g. ice pick, spike) more often. Compared with females, males tended to use less intense language to describe their pain. From PGI responses, participants identified as distressing: the pain itself (constancy, predictability and intensity) and the pain’s impact on mobility, mood and sleep. Intense pain and unpredictable pain were consistently ranked as more distressing than constant aching pain.
CONCLUSIONS: Two distinct types of pain were identified through focus groups and use of the PGI tool. Of these, intermittent but intense pain, particularly when not predictable, had a greater impact on quality of life than did background aching pain. These novel findings are being used to develop a new hip/knee OA pain measure.

 G.A. Hawker, None; L. Stewart, None; M.R. French, None; J. Cibere, None; J.M. Jordan, None; L. March, None; M. Suarez-Almazor, None; P. Dieppe, None.