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.


Central Sensitization and Knee Pain in Osteoarthritis: Preliminary Results from the MOST Study.

Neogi3,  Tuhina, Niu4,  Jingbo, Arendt-Nielsen1,  Lars, Scholz2,  Joachim, Frey-Law9,  Laura, Woolf2,  Clifford, Zhang4,  Yuqing

Aalborg University, Denmark
Boston Childrens Hospital
Boston Univ Schl of Med, Boston, MA
Boston Univ School of Medicine, Boston, MA
Boston University School of Medicine, Boston, MA
UCSF, San Francisco, CA
UCSF
University of Alabama at Birmingham
University of Iowa

Purpose:

Mechanisms contributing to knee pain in osteoarthritis (OA) are not well understood. Sustained mechanical and inflammatory stimuli in the joint may lead both to changes in the peripheral threshold of nociceptors (peripheral sensitization) and a central amplification of signals in the CNS (central sensitization), resulting in heightened pain sensitivity. We hypothesized findings of central sensitization may be associated with symptomatic knee OA (SxOA).

Methods:

The Multicenter Osteoarthritis (MOST) Study is cohort study of persons with or at high risk of knee OA. At the 60-month clinic visit, participants underwent knee radiography, answered pain questionnaires, and had an assessment of temporal summation (TS). TS is an augmented pain response to repetitive mechanical stimuli associated with central sensitization. A 60g monofilament was applied repeatedly over the skin of each patella at a frequency of 1 Hz for 30 seconds. TS was defined as being present when the subject reported an increase in pain following the mechanical stimulation at the site being tested. Knees were categorized according to presence of SxOA based on KL>=2 and presence of consistent frequent knee pain (answering yes to a question about frequent knee pain at a telephone screen and a subsequent clinic visit within 30 days). Pain severity was dichotomized as moderate or greater pain on any of the 5 knee-specific WOMAC pain questions versus none/mild. We used a within-person knee-matched approach to explore the relationships of interest while eliminating between-person confounding using matched conditional logistic regression. In the first matched analyses, we examined the relation of TS with presence of SxOA among persons with knees discordant for SxOA. In the second matched analyses, we examined the relation of TS with pain severity among persons with knees discordant for pain severity, adjusting for radiographic severity.

Results:

To date, data on 920 participants' 60-month clinic visit are available (mean age 68.0, mean BMI 30.8, 67.3% female). Among persons with no SxOA, unilateral SxOA, and bilateral SxOA, the age- and sex-adjusted prevalences of TS at the patella were: 59%, 60%, and 61%, respectively. In the within-person knee-matched analyses for SxOA (N=135 that met criteria), radiographic knee OA without regards to knee pain symptoms was associated with 2.3 times higher odds of TS than no OA (95% CI 1.1–4.8, p=0.03), but SxOA itself was not significantly associated with TS once radiographic severity was accounted for (crude OR 1.7, 95% CI 0.7–3.8, adjusted OR 1.1, 95% CI 0.3–3.4). For the knee-matched analyses regarding pain severity (N=152 that met criteria), TS was associated with WOMAC pain severity (OR 3.3, 95% CI 1.3–8.3), but this was attenuated when adjusting for radiographic severity (OR 2.6, 95% CI 0.7–9.5).

Conclusions:

In these preliminary results from a large cohort, TS was associated with the presence of radiographic knee OA and knee pain severity in the same knee, but not significantly with SxOA. Such findings suggest that the pathology of OA may be the source of prolonged sensory input required for central sensitization, and in turn, central sensitization may be related to pain severity.

To cite this abstract, please use the following information:
Neogi, Tuhina, Niu, Jingbo, Arendt-Nielsen, Lars, Scholz, Joachim, Frey-Law, Laura, Woolf, Clifford, et al; Central Sensitization and Knee Pain in Osteoarthritis: Preliminary Results from the MOST Study. [abstract]. Arthritis Rheum 2010;62 Suppl 10 :2098
DOI: 10.1002/art.29863

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