Relative difference among 27 functional measures in patients with knee osteoarthritis: an exploratory cross-sectional case-control study

To raise the effectiveness of interventions, clinicians should evaluate important biopsychosocial aspects of the patient’s situation. There is limited knowledge of which factors according to the International Classification of Function, Disability, and Health (ICF) are most deviant between patients with knee osteoarthritis (KOA) and healthy individuals. To assist in measures’ selection, we aimed to quantify the differences between patients with KOA and healthy controls on various measures across the ICF dimensions of body function, activity, and participation.

We performed an exploratory cross-sectional case-control study. In total, 28 patients with mild-to-moderate KOA (mean age 61 years, 64% women) referred by general physicians to a hospital’s osteoarthritis-school, and 31 healthy participants (mean age 55 years, 52% women), volunteered. We compared between-group differences on 27 physical and self-reported measures derived from treatment guidelines, trial recommendations, and trial/outcome reviews. Independent t-test, Chi-square, and Mann-Whitney U test evaluated the significance for continuous parametric, dichotomous, and ordinal data, respectively. For parametric data, effect sizes were calculated as Cohen’s d. For non-parametric data, ds were estimated by p-values and sample sizes according to statistical formulas. Finally, all ds were ranked and interpreted after Hopkins’ scale. An age-adjusted sensitivity-analysis on parametric data validated those conclusions.

Very large differences between patients and controls were found on the Pain numeric rating scale¹, the Knee Injury and Osteoarthritis Scale (KOOS, all subscales)², as well as the Örebro Musculoskeletal psychosocial scale³ (P < 0.0001). Large differences were found on the Timed 10-steps-up-and-down stair climb test⁴ and Accelerometer registered vigorous-intensity physical activity in daily life⁵ (P < 0.001). Respectively, these measures clustered on ICF as follows: ¹body function, ²all three ICF-dimensions, ³body function and participation, ⁴activity, and ⁵participation.

The limited sample excluded elderly patients with severe obesity.

Very large differences across all ICF dimensions were indicated for the KOOS and Örebro questionnaires together for patients aged 45–70 with KOA. Clinicians are suggested to use them as means of selecting supplementary measures with appropriate discriminative characteristics and clear links to effective therapy. Confirmative studies are needed to further validate these explorative and partly age-unadjusted conclusions.