Introduction Quantify motor cortex descending drive and voluntary activation in people with lower-limb osteoarthritis compared to controls.

Materials and Methods Systematic review and meta-analyses according to the PRISMA guidelines. Seven databases were searched until 30/12/2022. Studies assessing voluntary activation or responses to transcranial magnetic stimulation (TMS; i.e. motor evoked potential, intracortical facilitation, motor threshold, short-interval intracortical inhibition, and silent period) were included. Study quality was assessed using Joanna Briggs Institute criteria and evidence certainty using GRADE. Meta-analysis was performed using RevMan inverse variance, mixed-effect models.

Results Eighteen studies were included, all deemed low-quality. Quadriceps voluntary activation was impaired with knee osteoarthritis compared to healthy controls (standardised mean difference [SMD]=0.84, 95%CI= -1.12-0.56, low certainty). Voluntary activation of the more symptomatic limb was impaired (SMD= 0.42, 95%CI= -0.75-0.09, moderate certainty) compared to the other limb in people with hip/knee osteoarthritis . As only two studies assessed responses to TMS, very low certainty evidence demonstrated no significant difference between knee osteoarthritis and healthy controls for motor evoked potential, intracortical facilitation, resting motor threshold or short-interval intracortical inhibition.

Conclusions Low certainty evidence suggests people with knee osteoarthritis have substantial impairments in voluntary activation of their quadriceps muscle when compared to healthy controls. With moderate certainty we conclude that people with hip and knee osteoarthritis had larger impairments in voluntary activation of the quadriceps in their more painful limb compared to their non-affected/other limb.