Activation deficits do not limit quadriceps strength training gains in patients after total knee arthroplasty

Patients after total knee arthroplasty (TKA) are known to display deficits in quadriceps muscle activation. This study aimed to determine if quadriceps activation levels in patients after TKA at the beginning of rehabilitation would influence quadriceps strength following rehabilitation. Patients who underwent unilateral TKA (Men= 102; Female= 84) were included int the study.Voluntary activation of the quadriceps during maximal voluntary isometric contractions (MVIC) was measured using the central activation ratio (CAR). Hierarchical multivariate regression analysis was used to determine if CAR prior to treatment could predict MVIC after the strength training intervention. After controlling for age, sex, and initial strength levels (R2= 0.548; p<0.001), the predictability of quadriceps strength following the 6‐week intervention did not change when pain during MVIC (R2= 0.551; p= 0.317) and activation levels prior to rehabilitation (R2= 0.551; p= 0.818) were introduced into the regression.

Initial quadriceps activation levels, for patients who underwent TKA, failed to predict the quadriceps strength following a strength training intervention. Therefore, deficits in voluntarily activation post‐operatively should not be considered as a rate‐limiting factor in recovering quadriceps strength following TKA.