Neuromuscular Electrical Stimulation (NMES) for Improving Outcomes Following Total Knee Arthroplasty (TKA)

The current standard for rehabilitation after TKA consists of guided exercise therapy for up to 12 weeks after surgery. This includes inpatient, home, and outpatient therapy. The surgery and rehabilitation are highly successful at reducing or eliminating pain experienced preoperatively. However, quadriceps femoris muscle (QFM) strength, overall function, and knee range of motion are often worse than preoperative levels for as long as 6 months after surgery and in some cases may persist for many years after that. Such quadriceps strength impairments after TKA have been largely attributed to voluntary activation deficits and can lead to a decrease in functional performance such as decreased gait speed, decreased balance which can lead to falls, and decreased stair climbing & chair rise abilities. Since therapy alone does not adequately restore or improve upon the preoperative functional capabilities in a consistent and timely manner, it has been suggested that NMES used adjunctively with postoperative rehabilitation will alleviate the quadriceps muscle activation deficits. Early NMES use after TKA has been shown to: reduce knee extensor lag, increase walking speed, and improve QFM strength, knee range of motion, and function. However, NMES initiated one month after TKA did not lead to improved QFM strength or function beyond the standard benefits gained from exercise alone, thus suggesting that the timing of NMES application after TKA is important. It has previously been shown that preoperative QFM strength is predictive of postoperative function [6] but the benefit of prehabilitation remains in question. To date, there has only been one pilot study assessing the benefits of NMES when initiated preoperatively. This study only included 14 patients (9 NMES, 5 control) but was able to show that preoperative NMES usage may lead to greater QFM strength gains after TKA. Therefore, it will be important to assess the benefits of NMES both preoperatively and postoperatively in order to determine how it will be most beneficial to TKA patients.