Exercise-induced hypoalgesia (EIH), a measure of descending pain inhibitory control, has been found hyperalgesic in subgroups of painful knee osteoarthritis (KOA) patients. The effect of standardized exercise therapy (ET) on clinical pain intensity in KOA has been demonstrated. However, the prognostic value of EIH in KOA patients completing an ET program has not been investigated. This study investigated the prognostic value of EIH on pain relief following ET in KOA patients.
In 24 painful KOA patients (Numerical Rating Scale, 0 to 10 ≥3), EIH was assessed as change in pressure pain threshold after 2-minute “lateral raises” before and after ET in this observational study. In addition, temporal summation of pain, clinical pain scores (Numerical Rating Scale, Knee injury and Osteoarthritis Outcome Score [KOOS], and PainDETECT Questionnaire) were assessed before and after ET. The KOOS-4 is defined by the KOOS subscale scores for Pain, Symptoms, Activities of Daily Living, and Quality of Life and was used as the primary outcome.
Following ET, all clinical pain scores improved (P<0.01) but no changes in pressure pain threshold, temporal summation of pain, or EIH were found (P>0.05). Linear regression models identified pretreatment EIH (β=0.59, P<0.005) and PainDETECT Questionnaire (β=0.57, P<0.005) as independent factors for relative change in KOOS-4 after ET (adjusted R2=46.8%).
These preliminary and exploratory results suggest that patients with a high EIH response before a standardized ET program may be associated with a large improvement in pain after treatment. This measure may potentially help clinicians as a prognostic tool for outcome prediction following ET in KOA patients.
*Department of Health Science and Technology, Center for Sensory-Motor Interaction (SMI)
§Department of Health Science and Technology, Center for Neuroplasticity and Pain, Faculty of Medicine, Aalborg University, Aalborg
†Department of Anesthesiology and Intensive Care Medicine, Pain Research Group, Pain Center, University Hospital Odense
‡Department of Clinical Research, Faculty of Health Sciences, University of Southern Denmark, Odense, Denmark
K.K.P. is supported by The Aalborg University Talent Management Program, Aalborg, Denmark (j.no. 771126). Center for Neuroplasticity and Pain (CNAP) is supported by the Danish National Research Foundation, Copenhagen, Denmark (DNRF121). The authors declare no conflict of interest.
Reprints: Kristian K. Petersen, MSc, PhD, Department of Health Science and Technology, Center for Sensory-Motor Interaction (SMI), Faculty of Medicine, Aalborg University, Frederik Bajers Vej 7 D3, Aalborg DK-9220, Denmark (e-mail: email@example.com).
Received May 22, 2019
Received in revised form September 10, 2019
Accepted September 17, 2019
Online date: September 23, 2019