Surface Electromyography Assessment-Guided Strengthening Exercises Considering Vastus Medialis and Vastus Lateralis Activation After Total Knee Arthroplasty: A Case Report

Reduced vastus medialis (VM) and vastus lateralis (VL) muscle activity after total knee arthroplasty (TKA) delays recovery of gait ability and activities of daily living.However, few studies have evaluated the muscle activity characteristics of the VM and VL using surface electromyography (SEMG) and used these findings to guide the selection of exercise tasks.Therefore, this case report describes the clinical course of a patient after an SEMG-guided exercise intervention in which exercise tasks eliciting the greatest muscle activation in the VM and VL were selected.A male patient in his 70s underwent TKA for right knee osteoarthritis.From postoperative day 1, range-of-motion exercises, strengthening exercises, gait training, and ADL training were initiated.From postoperative day 14, the muscle activity of the rectus femoris (RF), VM, and VL was assessed using SEMG during eight knee extension exercise tasks, and root mean square (RMS) values were calculated.The VM showed the highest RMS value during seated knee extension at 90° of knee flexion (SIT 90), whereas the VL showed the highest RMS value during maximal straight leg raise (SLR max).Therefore, these two exercise tasks were performed as strengthening exercises from postoperative days 14 to 56.The knee range of motion, extension lag, manual muscle testing, and pain intensity improved on postoperative day 56 compared with those on postoperative day 14.Additionally, the RMS values of the VM and VL and the VM/RF and VL/RF ratios increased, indicating a change in the RF-dominant muscle activity pattern.This case indicates that selecting exercise tasks according to the muscle activity characteristics of the VM and VL based on SEMG assessment may be a useful approach to quadriceps strengthening after TKA.Further controlled studies are needed to verify the effectiveness of this approach.