Relation of pain sensitization to knee loading during walking in people with knee osteoarthritis

To examine the association of pain sensitization with knee joint loading during walking in people with knee osteoarthritis (OA).

For this cross-sectional study, we used baseline data from participants with symptomatic knee OA (n=104) enrolled in two clinical trials. We used pressure pain threshold (PPT) at the knee and wrist to assess sensitization. Using gait analyses during walking, we derived peaks and impulse of knee adduction moment (KAM) and knee flexion moment, and frontal and sagittal plane range of motion during stance. We used an Analysis of Covariance (ANCOVA) adjusted for age, sex, body height, and body weight to examine associations of PPT (sex-specific tertiles) with gait outcomes. Sensitivity analyses included additional adjustment for gait speed.

For knee PPT, the lowest tertile had a lower 1st peak of KAM (∆=9.1 Nm [95% CI; 0.3, 17.9]) compared to the highest tertile. For wrist PPT, when compared to the highest tertile, the lowest tertile had a lower 1st peak of KAM (∆=9.1 Nm [1.3, 16.8]), a lower 2nd peak of KAM (∆=7.5 Nm [0.5, 14.6]), and a lower KAM impulse (∆=1.7 Nm*s [0.1, 3.2]), while the middle tertile also had a lower 2nd peak of KAM (∆=8.0 Nm [0.7, 15.4]) and a lower KAM impulse (∆=2.0 Nm*s [0.4, 3.6]). The effect sizes for other gait measures were small and clinically not meaningful. These effect sizes remained similar after adjusting for gait speed.

Greater pain sensitivity, as assessed by PPT, was related to lower frontal plane joint loading during walking. These findings may reflect a motor adaptation to nociceptive alterations in this population.