Arthritis & Rheumatism, Volume 62,
November 2010 Abstract Supplement

Abstracts of the American College of
Rheumatology/Association of Rheumatology Health Professionals
Annual Scientific Meeting
Atlanta, Georgia November 6-11, 2010.

Unpredictability of Intermittent Knee OA Pain Impact on Pain, Function and Mood.

Hawker2,  Gillian A., French3,  Melissa R., Elkayam3,  Joy G., Davis1,  Aileen M.

Toronto Western Research Insti, Toronto, ON, Canada
Women's College Hospital, Toronto, ON, Canada
Women's College Hospital, Toronto, Canada


In people with painful knee osteoarthritis (OA), focus groups identified the predictability of the pain as a key determinant of the pain impact. This study evaluated the effects of unpredictable knee pain (without warning) and pain after a trigger on the pain experience, physical functioning and mood in people with knee OA. We hypothesized that unpredictable knee pain would be associated with greater pain, worse physical functioning and more depressed mood than would predictable knee pain.


In a cohort with hip and knee OA, participants completed the OARSI-OMERACT Intermittent and Constant Osteoarthritis Pain (ICOAP) measure, WOMAC, and a measure of depressed mood (CES-D). For each symptomatic knee, those with intermittent knee pain were asked how often their pain occurs 'without warning' (unpredictable pain) or 'after a specific trigger', e.g. an activity (predictable pain) (0, never, to 4, very often). For those without hip complaints, the proportions with each type of intermittent pain were calculated (at least sometimes versus never/rarely). The relationships between type of intermittent pain and ICOAP and WOMAC scores were evaluated using linear regression. For each type of intermittent pain, we examined the relationship between the number of knees affected (0, 1 or 2) and ICOAP and WOMAC scores using Wilcoxon Rank Sum tests. We examined the relationship between each type of intermittent pain and depressed mood (CES-D scores), controlling for age, sex and arthritis severity (WOMAC summary score).


The mean age of the 116 knee OA participants was 79.7 years (64.0 to 93.2); 74.1% were female and 23.4% had < high school education. 103 subjects (88.8%) reported intermittent knee pain in at least one knee; of these, 18.1% (n=21) had pain only after a trigger, 12.9% (n=15) had only unpredictable pain, while 44.0% (n=51) had both types of intermittent pain. Controlling for age and sex, unpredictable knee pain in one or both knees was independently associated with higher ICOAP and WOMAC scores (p<0.05 for all). Controlling for unpredictable knee pain, knee pain after a trigger was independently associated only with higher scores on the ICOAP intermittent scale (p=0.01). A greater number of knees with unpredictable pain was associated with higher ICOAP intermittent (p<0.0001) and WOMAC summary (p=0.01) scores. For pain after a trigger, this relationship was found only with ICOAP intermittent scores (p<0.0001). Controlling for age, sex and arthritis severity, unpredictable knee pain, but not knee pain after a trigger, was independently associated with higher scores for depressed mood (p=0.005).


Both unpredictable pain and pain following a trigger occur commonly in people with chronic symptomatic knee OA. Compared with pain following a trigger, unpredictable knee pain is associated with greater pain and functional disability, and more depressed mood. Studies are needed to identify potentially modifiable risk factors for unpredictable knee OA pain in order to develop and test interventions to relieve this complaint.

To cite this abstract, please use the following information:
Hawker, Gillian A., French, Melissa R., Elkayam, Joy G., Davis, Aileen M.; Unpredictability of Intermittent Knee OA Pain Impact on Pain, Function and Mood. [abstract]. Arthritis Rheum 2010;62 Suppl 10 :682
DOI: 10.1002/art.28450

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