Pain among individuals with knee osteoarthritis (OA) is associated with significant disability in older adults, and recent evidence demonstrates enhanced experimental pain sensitivity. Although previous research showed considerable heterogeneity in the OA clinical pain presentation, less is known regarding the variability in responses to experimental pain. The present study included individuals with knee OA (n = 292) who participated in the Understanding Pain and Limitations in Osteoarthritic Disease study and completed demographic and psychological questionnaires followed by a multimodal quantitative sensory testing (QST) session. Quantitative sensory testing measures were subjected to variable reduction procedures to derive pain sensitivity index scores, which in turn were entered into a cluster analysis. Five clusters were significantly different across all pain sensitivity index variables (P < 0.001) and were characterized by: (1) low pain sensitivity to pressure pain (N = 39); (2) average pain sensitivity across most modalities (N = 88); (3) high temporal summation of punctate pain (N = 38); (4) high cold pain sensitivity (N = 80); and (5) high sensitivity to heat pain and temporal summation of heat pain (N = 41). Clusters differed significantly by race, gender, somatic reactivity, and catastrophizing (P < 0.05). Our findings support the notion that there are distinct subgroups or phenotypes based on experimental pain sensitivity in community-dwelling older adults with knee OA, expanding previous findings of similar cluster characterizations in healthy adults. Future research is needed to further understand the pathophysiological mechanisms underlying pain within these subgroups, which may be of added value in tailoring effective treatments for people with OA.
Our results support the hypothesis that different phenotypic profiles exist within persons with knee osteoarthritis. Our experimental pain-based groupings differed in demographic, psychological, and clinical characteristics.
aPain Research and Intervention Center of Excellence (PRICE), University of Florida, Gainesville, FL, USA
bDepartment of Community Dentistry and Behavioral Science, University of Florida, Gainesville, FL, USA
Departments of cBiobehavioral Nursing Science and
dAging and Geriatric Research, University of Florida, Gainesville, FL, USA
eDepartment of Psychology, University of Alabama at Birmingham, Birmingham, AL, USA
fDivision of Clinical Immunology and Rheumatology, University of Alabama at Birmingham, Birmingham, AL, USA
gDepartment of Medicine, University of Florida, Gainesville, FL, USA
Departments of hBiostatistics and
iMedicine and Rheumatology, University of Alabama at Birmingham, Birmingham, AL, USA
Corresponding author. Address: Department of Aging & Geriatric Research, Institute on Aging Cognitive Aging & Memory Clinical Translational Research Program (CAM-CTRP), College of Medicine, University of Florida, 2004 Mowry Rd, Suite 2144, Gainesville, FL 32607. Tel.: 352-294-5845. E-mail address: email@example.com (Y. Cruz-Almeida).
Sponsorships or competing interests that may be relevant to content are disclosed at the end of this article.
Received January 13, 2016
Received in revised form April 05, 2016
Accepted April 14, 2016