Psychometric Properties of the Knee Osteoarthritis Pain Index

Scott G Ravyts; Timothy R Fleagle; Elena Staguhn; Daniel Scharfstein; Rachel V Aaron; Steven Paul Cohen; Robert W Hurley; Srinivasa N Raja; Jennifer Haythornthwaite; Lauren Allen; Robert R Edwards; Lars Arendt-Nielsen; Claudia M Campbell; Renan Castillo

doi:10.1093/pm/pnaf067

Psychometric Properties of the Knee Osteoarthritis Pain Index

Pain Med. 2025 May 26:pnaf067. doi: 10.1093/pm/pnaf067. Online ahead of print.

Affiliations

¹ Department of Psychological Science, University of North Carolina at Charlotte.
² Department of Physical Therapy and Rehabilitation Science, University of Iowa Carver College of Medicine.
³ Department of Health Policy and Management, Johns Hopkins School of Public Health.
⁴ Department of Health Population Sciences, University of Utah School of Medicine.
⁵ Department of Physical Medicine & Rehabilitation, Johns Hopkins School of Medicine.
⁶ Departments of Anesthesiology, Neurology, Physical Medicine and Rehabilitation, Psychiatry, and Neurological Surgery, Northwestern University Feinberg School of Medicine, Departments of Anesthesiology and Physical Medicine and Rehabilitation, Walter Reed National Military Medical Center, Uniformed Services University of the Health Sciences.
⁷ Departments of Anesthesiology, Translational Neuroscience, and Public Health, Wake Forest University School of Medicine.
⁸ Department of Anesthesiology and Critical Care Medicine, Johns Hopkins School of Medicine.
⁹ Department of Psychiatry & Behavioral Sciences, Johns Hopkins School of Medicine.
¹⁰ Department of Anesthesiology, Perioperative & Pain Medicine, Harvard Medical School/Brigham & Women's Hospital.
¹¹ Center for Neuroplasticity and Pain (CNAP), Department of Health Science and Technology, School of Medicine, Aalborg University, Department of Gastroenterology & Hepatology, Mech-Sense, Clinical Institute, Aalborg University Hospital, Steno Diabetes Center North Denmark, Clinical Institute, Aalborg University Hospital.

PMID: 40418215
DOI: 10.1093/pm/pnaf067

Abstract

Objectives: The current study sought to evaluate the psychometric properties of a newly developed Knee OsteoArthritis Pain Index (KOAPI), derived from the Brief Pain Inventory (BPI), among individuals with knee osteoarthritis (KOA).

Methods: This study consisted of secondary data analysis of two clinical trials. In study 1, 241 individuals with KOA were evaluated before total knee arthroplasty and six months post-surgery. In study 2, 37 individuals with KOA participated in a randomized, double-blind, placebo controlled, two-way crossover study in which they received either a COX-2 inhibitor followed by a placebo or a placebo followed by a COX-2 inhibitor. The KOAPI was derived from the BPI and included three BPI pain severity items (worst, average, current) and the BPI pain interference item related to pain when walking.

Results: The KOAPI showed excellent model fit (CFI = 0.99; TFI: 0.98-0.99; RMSEA: 0.08-0.001), good reliability (Cronbach's alpha: 0.84-0.87) and high convergent validity with the Western Ontario and McMaster Universities Osteoarthritis Index (r = 0.66; 95% CI: 0.44, 0.81) and the Pain Catastrophizing Scale (r = 0.50; 95% CI: 0.39, 0.60).

Conclusions: Overall, the psychometric properties of the KOAPI were comparable or better than those produced by the original BPI pain severity subscale. The KOAPI may be a helpful screening and outcome measure for individuals with KOA that more closely captures symptoms which drive patients to seek clinical care.

Keywords: Osteoarthritis; knee; pain; psychometrics.

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