Pain severity reduction in subjects with knee osteoarthritis decreases motor-cognitive dual-task costs.

Background: Pain has disruptive effects on cognitive functions leading to a decreased capability to multi task. This might be the reason why pain is a fall risk factor in dual-task situations. This study aims to relate a decrease/increase in pain severity with a decrease/increase in dual-task costs of gait variability, which is associated with fall risk, in patients with osteoarthritis prior to and 6-8weeks after total knee replacement.

Methods: We assessed the variability of minimum toe clearance in normal walking and dual-task walking in 36 patients (14 male and 22 female participants; age=mean 64.4, SD (9.2) years) with knee osteoarthritis one day before total knee replacement and again 6-8weeks after the operation. We assessed pain severity with the Brief Pain Inventory. Dual-task costs were calculated as the percentage change of gait variability from single-task walking to dual-task walking. We subtracted the post-test values from the pre-test values of both outcomes to get absolute changes. We calculated the correlation using Kendall's Tau.

Findings: Subjects with a high difference of pain severity were more likely to have higher differences of dual-task costs of gait variability (rτ=0.416, p=0.000).

Interpretation: Our data suggest that a reduction of pain severity goes along with a reduction in dual-task costs. This indicates that pain might have substantial influence on fall risk in daily-life multi-task situations due to its detrimental effects on cognitive processes which may be adequately addressable by interventions that alleviate pain.