Neuromuscular activation of quadriceps bellies during tasks performed in the same biomechanical condition in patients undergoing total knee arthroplasty

Abstract

Objective: To investigate neuromuscular activation of quadriceps bellies during different tasks in patients before and after total knee arthroplasty (TKA).

Methods: Twenty-six patients scheduled for TKA and 16 control subjects performed three isometric tasks: knee extension (KE), hip flexion (HF), hip flexion with contralateral hip extension (HFE). Surface electromyography signals of rectus femoris, vastus medialis and vastus lateralis were collected the day before (T0), at one (T1) and three (T2) days after surgery, whereas control subjects underwent a single evaluation. The Root Mean Square peak normalized for its highest value during the three tasks (nRMS-peak) was used as index of maximum neuromuscular activation for each belly. Sixteen patients performed the postoperative assessment, due to the placement of an elastomeric pump aimed at reducing pain in 10 patients.

Results: Patients showed lower rectus femoris nRMS-peak during KE compared to HF and HFE before and after surgery (p < 0.001), as occurred in control subjects. Differently from control subjects, patients showed higher vastus medialis and vastus lateralis nRMS-peak during HF compared to KE at T1 (p = 0.008) and T2 (p = 0.039).

Conclusion: TKA modified quadriceps neuromuscular activation during different tasks performed the same biomechanical condition. These findings may be considered in planning physiotherapy interventions after TKA.

Keywords: Neuromuscular activation deficits; Quadriceps femoris; Total knee arthroplasty.