Medial meniscal extrusion with cumulative mechanical stress describes the clinical response of lateral wedge insoles for patients with knee osteoarthritis.

Abstract

Lateral wedge insole (LWI) is known to reduce abnormal mechanical stress in knee osteoarthritis; however, clinical improvement across cases varies. The increase in medial meniscal extrusion (⊿MME) during walking could describe the dysfunction of shock absolution and the reaction of mechanical stress in individual knee joints. This study aimed to investigate whether the ⊿MME affects LWI responders. Quasi-experimental design. The ⊿MME during walking was assessed using a dynamic ultrasound technique. Knee adduction moment was evaluated using motion analysis. The activity of the patients during the study period was evaluated as the number of steps counted by the acceleration sensor, and the cumulative knee adduction moment (CKAM) was calculated. These parameters were obtained at the initial visit (baseline) and after intervention with LWI after 3 months (post-LWI), and are expressed as the rates of change. The global rating of change was assessed and compared after the intervention; the patients were classified as responders or nonresponders accordingly. Responders had a significantly higher reduction rate of ⊿MME than nonresponders (responder: 33.6% ± 14.4%, nonresponder: 14.8% ± 26.9%; P = 0.035), whereas there was no significant difference in rates of change in the number of steps, knee adduction moment, and CKAM between groups. The ⊿MME was significantly correlated with CKAM among the parameters of rates of change (r = 0.416, P = 0.034). Reduction in mechanical stress in a laboratory setting does not directly affect the clinical response to LWI. The functional features of the meniscal hoop during walking can mediate the response to mechanical stress and help elucidate pain-relief mechanisms.