Dynamic weight-bearing assessment of pain in knee osteoarthritis: construct validity, responsiveness, and interpretability in a research setting.
BACKGROUND
The Osteoarthritis Research Society International (OARSI) has suggested to asses pain after specific activities consistently in clinical trials on knee OA. The Dynamic weight-bearing Assessment of Pain (DAP) assesses pain during activity (30 s of performing repeated deep knee-bends from a standing position). The purpose of this study is to evaluate the construct validity, responsiveness, and interpretability of the DAP for knee osteoarthritis (OA).


METHODS
One-hundred participants with knee OA were tested twice each with the DAP, the Knee injury and Osteoarthritis Outcome Score (KOOS), six-minute-walk-test (6MWT), and 6-min-walk-test with subsequent pain rating (6MWTpain), and once with a transition questionnaire (TRANS-Q) for the patient-reported change in pain after 12 weeks of exercise. Construct validity (baseline-scores) and responsiveness (change-scores) were estimated by Spearman Correlation Coefficients. We hypothesized that no correlations would be excellent (<0.7) (divergent validity), except for the 6MWTpain (convergent validity). The TRANS-Q was used for interpreting the DAP change-scores in terms of responsiveness and Minimal Important Change (MIC).


RESULTS
Divergent validity with the KOOS subscales (r = -0.31 to-0.45) and the 6MWT (r = -0.25) was supported. Convergent validity with the 6MWTpain was not supported (r = 0.54). The DAP change-scores corresponded to patient-reported change in pain (TRANS-Q), while correlations with change-scores on the other instruments were <0.35. The MIC was 2.4 DAP points.


CONCLUSIONS
The DAP possesses divergent validity compared to other instruments for knee OA, supporting the potential for this new way of assessing pain directly during activity. Importantly, the DAP change-scores correspond to patient-reported changes in pain, showing responsiveness. A change of 2.4 or more can be interpreted as clinically relevant. The DAP is a promising alternative to using 'pain on walking' as a clinical trial inclusion criterion/outcome.
The Parker Institute, Bispebjerg & Frederiksberg Hospital, Nordre Fasanvej 57, 2000, Frederiksberg, Copenhagen, Denmark. Louise.Klokker.Madsen@regionh.dk.
Louise
http://orcid.org/0000-0003-2463-0990
L
Klokker
The Parker Institute, Bispebjerg & Frederiksberg Hospital, Nordre Fasanvej 57, 2000, Frederiksberg, Copenhagen, Denmark.
Robin
R
Christensen
The Parker Institute, Bispebjerg & Frederiksberg Hospital, Nordre Fasanvej 57, 2000, Frederiksberg, Copenhagen, Denmark.|The Research Initiative for Activity studies and Occupational Therapy, Institute of Public Health, University of Southern Denmark, Odense, Denmark.
Eva E
EE
Wæhrens
The Parker Institute, Bispebjerg & Frederiksberg Hospital, Nordre Fasanvej 57, 2000, Frederiksberg, Copenhagen, Denmark.
Elisabeth
E
Bandak
The Parker Institute, Bispebjerg & Frederiksberg Hospital, Nordre Fasanvej 57, 2000, Frederiksberg, Copenhagen, Denmark.
Cecilie
C
Bartholdy
The Parker Institute, Bispebjerg & Frederiksberg Hospital, Nordre Fasanvej 57, 2000, Frederiksberg, Copenhagen, Denmark.
Henning
H
Bliddal
The Parker Institute, Bispebjerg & Frederiksberg Hospital, Nordre Fasanvej 57, 2000, Frederiksberg, Copenhagen, Denmark.|Department of Physical and Occupational Therapy, Bispebjerg & Frederiksberg Hospital, Copenhagen, Denmark.
Marius
M
Henriksen
D000328:Adult; D000368:Aged; D005080:Exercise Test; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000150:complications / Q000503:physiopathology*; D010146:Pain / Q000175:diagnosis* / Q000209:etiology / Q000503:physiopathology; D010147:Pain Measurement / Q000379:methods*; D011788:Quality of Life; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D011795:Surveys and Questionnaires; D016138:Walking / Q000502:physiology; D016474:Weight-Bearing / Q000502:physiology*
Activity; Knee osteoarthritis; Outcome measure; Pain