People with hip osteoarthritis have reduced quadriceps voluntary activation and altered motor cortex function

Compare quadriceps voluntary activation, corticospinal and intracortical excitability between people with and without hip osteoarthritis (OA). Exploratory objectives include quantifying the association of corticospinal/intracortical excitability with voluntary activation, corticospinal/intracortical excitability with hip related pain, and motor threshold with motor cortex inhibition and facilitation.

Case-control study including participants with clinically and radiologically confirmed hip OA and non-OA controls. Quadriceps voluntary activation was assessed using twitch interpolation via femoral nerve stimulation. Single- and paired-pulse transcranial magnetic stimulation over the motor cortex assessed resting motor threshold (RMT), active motor threshold (AMT), short-interval intracortical inhibition (SICI), intracortical facilitation (ICF) and silent period. Generalized linear models assessed outcomes (p ​< ​0.05).

We included 17 hip OA (76% female) and 24 controls (92% female) with a mean (standard deviation) age of 58.7 (7.9) years. Compared to controls, people with hip OA had reduced quadriceps voluntary activation (β ​= ​-5.29, 95% confidence intervals [CI], -0.79--9.79) and increased ICF (β ​= ​0.22, 95%CI, 0.01-0.43). People with hip OA did not differ from controls in RMT (β ​= ​-4.76, 95%CI, -14.08-4.56), AMT (β ​= ​-2.13, 95%CI, -7.12-2.86), SICI (β ​= ​-0.02, 95%CI, -0.15-0.006) or silent period (β = 8.72, 95%CI, -24.75-42.20). More facilitation was associated with increased hip pain (β = 24.55, 95%CI, 6.93-42.18), and more inhibition was associated with less voluntary activation (β = 10.50, 95%CI, 2.00-18.99).

People with hip OA demonstrate reduced quadriceps voluntary activation and complex changes in motor cortex excitability compared to controls. These findings suggest that hip OA can alter quadriceps neuromuscular function (facilitation associated with pain, inhibition associated with activation), thus having implications for rehabilitation.