Criteria for knee flexion range of motion and quadriceps strength to ascend and descend stairs 1 year after bilateral total knee arthroplasty: A cross-sectional study

BackgroundStair ascent/descent pose significant challenges after total knee arthroplasty (TKA); however, the exact knee flexion range of motion (ROM) and quadriceps strength requirements remain unclear.ObjectiveTo establish criteria for knee flexion ROM and quadriceps strength to determine independence in stair ascent/descent and evaluate the accuracy of the combination of these factors in patients with bilateral TKA.MethodsPatients with bilateral TKA were cross-sectionally assessed at 1 year postoperatively for independence in stair ascent/descent. Receiver operating characteristic curves provided cutoff values for knee flexion ROM and quadriceps strength. The area under the curves (AUC) of each factor and logistic regression models including both factors were evaluated.ResultsEighty-two participants were included. Fifty-eight participants could independently ascend and 52 could descend stairs, with equal cutoff values for both: 121° for knee flexion ROM (AUC: 0.66 and 0.67) and 1.09 Nm/kg for quadriceps strength (AUC: 0.70 and 0.73). Logistic regression models produced AUCs of 0.73 and 0.76 for ascent and descent, respectively.ConclusionsA quadriceps strength of 1.09 Nm/kg is a useful cutoff for independent stair ascent/descent, but combining it with knee flexion ROM did not enhance accuracy. Other functions such as coordination of the knee or other joints may influence stair performance post-TKA.