Femoral quadriceps neuromuscular electrical stimulation after total knee arthroplasty: a systematic review

ABSTRACT The purpose of this study was to evaluate the effects of neuromuscular electrical stimulation in patients submitted to total knee arthroplasty. This was a systematic review with no language or publication status restriction. Our search was made in Cochrane Library, MEDLINE, Embase and LILACS. Randomized or quasi-randomized clinical trials evaluating neuromuscular electrical stimulation after total knee arthroplasty were included. Four studies with moderate risk of bias and low statistical power were included, totalizing 376 participants. There was no statistically significant difference in knee function, pain and range of motion during 12 month follow-up. This review concluded that neuromuscular electrical stimulation was less effective than traditional rehabilitation in function, muscular strength and range of motion. However, this technique was useful for quadriceps activation during the first days after surgery.


INTRODUCTION
Osteoarthritis is a degenerative joint disease characterized by reduction of articular cartilage in some areas, and can be related to bone hypertrophy (osteophytes and subchondral bone sclerosis) resulting from biochemical alterations and biomechanical stresses. It is estimated that 75% of the population aged over 65 years is affected by this disease, with a higher prevalence in women, mostly at the knee joint. (1,2) All the above-mentioned alterations result in quality of life reduction due to functional limitation. Knee arthroplasty is a common and effective intervention for knee osteoarthritis treatment when the clinical therapy is unsuccessful. Its applicability grew 73% at the last 10 years and it is expected that its indication rises more than 600% (3.48 million procedures) until 2030. (3) Such percent growth in total knee arthroplasty (TKA), first introduced in the 1960s, is due to pain relief and range of motion (ROM) gain. TKA main goal is to reestablish the patient's joint compromised function. This is why TKA is considered as one of the most important surgery developments of this century. On the United States alone, currently nearly 140 thousand TKAs are performed each year. However, surgery itself is not capable to restore the patient's complete functionality. Physical therapy is an integral part of treatment, yielding the best results regarding postoperative pain, physical function and quality of life. (4) As such, early rehabilitation start following TKA significantly benefits joint mobility and muscle stretch gain, favoring important quality of life gains and preventing postoperative complications. Apart from the primary benefits, the immediate rehabilitation could reduce hospital stay and improve the joint functional ability in the short and medium-run. (5) Another study showed joint pain relief and gait velocity and cadence improvement. (6) Labraca et al. (2) showed that, despite the few scientific evidences, isometric and isotonic exercises designed for quadriceps strengthening between zero and 30° of flexion, ROM gain and inferior limb muscle stretching are usually employed with good results.
Other studies showed that postoperative weakness, muscle atrophy and knee function alterations are common during the first 4 weeks after surgery, causing a quadriceps strength déficit compared to the contralateral limb that reaches a 18% reduction. (7,8) Although the neurophysiologic mechanisms for quadriceps muscle voluntary activation déficits are not fully understood, spinal reflex activity from swelling or pain in the knee joint may change afferent input from the injured joint and result in diminished efferent motor drive to the quadriceps muscle (also referred to as "reflex inhibition") that reduces muscle strength. (9,10) One of the measures to reduce voluntary activation deficits and prevent muscle atrophy after TKA is the neuromuscular electrical stimulation (NMES) as an adjuvant restoring normal knee function. (9) OBJECTIVE Based on the previously mentioned literature, the objective of this review was to systematically evaluate the effects (benefits and harms) of neuromuscular electrical stimulation in patients who underwent to total knee arthroplasty.

Data sources and searches
Institutional review board approval (number 1,593-12) was obtained to perform this systematic review. The study was registered at -International Prospective Register of Systematic Reviews (Prospero), protocol CRD42013005491.

Types of studies
We included randomized or quasi-randomized (in which participants therapy-allocation was not strictly random, i.e., using hospital register number, alternation, medical file number etc.) clinical trials evaluating physical therapy interventions with NMES after TKA.

Types of participants
We included studies that evaluated (skeletally mature) adults who underwent rehabilitation with NMES after TKA.

Types of intervention
All physical therapy interventions used at post-TKA treatment associated with NMES were considered. We compared NMES with physical therapy rehabilitation.
Studies comparing non-physical therapy-related or specific formation rehabilitation techniques (including Mulligan, Maitland, Pilates etc.) were excluded. http://www.controlled-trials.com) and Clinical Trials (at www.clinicaltrials.gov) for ongoing and recently completed studies. There were no language or publication status-based restrictions.
At MEDLINE (PubMed), a specific filter (sensitivity and maximum precision version) for randomized clinical trials identification was combined to a specific subject strategy. (13) Search strategies were also performed at The Cochrane Library (Wiley InterScience), Embase (Elsevier) and LILACS (Bireme) as described in appendix 1.

Searching other resources
We checked the reference lists of articles and reviews for possible relevant studies.

Study selection
Two authors independently selected potential eligible titles and abstracts to be included on this review and extracted data using pre-piloted form. Any disagreements were resolved by discussion and, when necessary, with adjudication by a third author. Authors were not blinded to journal and/or authors.

Data extraction and management
Two authors collected the following data using a prepiloted data extraction form: study methodology characteristics, including study design and duration and the protocol publication prior patient recruitment; financing sources and register details; study participants characteristics, with study site, number of enrolled participants, number of evaluated participants, inclusion criteria, exclusion criteria, participants' age, prosthesis types and surgical techniques; study intervention characteristics, including intervention time, physical therapy intervention and other co-intervention types; study result characteristics, including follow-up time, loss at follow-up and outcome measures; and methodological domains, as described below at the risk of bias evaluation section. Any discrepancies were settled by a third reviewer. Two review authors inputted the data at Review Manager TM .

Assessment of risk of bias in the included studies
The risk of bias of the included studies was independently evaluated by two authors. As recommended by The Cochrane Collaboration's "Risk of bias" tool, (14) the following domains were assessed: random sequence generation; allocation concealment; blinding of participants and personnel; blinding of outcome assessment; incomplete outcome data; selective reporting; other bias (e.g., great imbalance between participants groups and risk of bias associated with testers and other caretakers' inexperience).
Each individual criterion was deemed as presenting low risk of bias, high risk of bias and uncertain risk of bias (lack of information or uncertainties regarding potential bias). Discrepancies between authors were solved based on a consensus.

Measures of treatment effect
The risk ratio with a 95% confidence interval (95%CI) was calculated for dichotomous variables. Continuous variables results were expressed as mean differences (MD) with 95%CI.

Unit of analysis issues
At the studies included in this review, randomization was based on individual participants. Exceptionally, as in clinical trials including patients with bilateral knee prostheses, data may have been laterally evaluated rather than by individual patients. During the analysis of questions lacking proper corrections, the presentation of such clinical trials data was considered only when discrepancies between analysis units and randomization were small. After data compilation, a sensitivity analysis was performed to examine the effects of the incorrectly evaluated clinical trials in the studies correctly addressed.

Dealing with missing data
The data on outcome were extracted for all randomized patients. When required, the primary study authors were contacted to request missing data, with participant number, sampling loss details, uncertainty measures (standard deviation or error) or number of events.
The standard deviation of continuous variables, with no report of such figure, was calculated using p value and values (95CI%). (14) The impossibility of sampling loss data obtainment was described at the risk of bias table, including a discussion regarding the potential influence of such data at the results and conclusions of the present review. Sensitivity analysis was applied in order to explore these missing data effects. (15)

Assessment of heterogeneity
We assessed the heterogeneity of estimate effects between the included studies by visual inspection of the forest plot and using the I² statistic.
We quantified the possible magnitude of inconsistency (i.e. heterogeneity) across studies, using the I 2 statistic with a rough guide for interpretation as follows: zero to 40% might not be important; 30% to 60% may represent moderate heterogeneity; 50% to 90% may represent substantial heterogeneity; and 75% to 100% considerable heterogeneity. (14) In cases of considerable heterogeneity (defined as I 2 75%), we explored the data further by comparing the characteristics of individual studies and conducting subgroup analyses.

Assessment of reporting biases
For meta-analysis with more than ten studies, primary outcomes graphs were draw in order to evaluate the potential publication bias (small studies effects). The presence of bias was also evaluated in small studies, to verify if random intervention events were more beneficial compared to fixed events estimative. (16) Data synthesis When appropriate, results of comparable groups of studies were pooled in meta-analysis using the random-effects model as a default. For dichotomous outcomes, RR and 95%CI were calculated. When two or more studies presented continuous data from the same validated instrument of evaluation using the same units of measure, data were pooled as a MD with 95%CI. When primary studies state the same variable using different instruments and different units of measure, we used the standardized mean difference with 95%CI.

Subgroup analysis and investigation of heterogeneity
Subgroup analysis for following demographics was planned: age (adolescents, adults and people older than 65); type of surgical intervention TKA; and rehabilitation start (outpatient and inpatient).

Sensitivity analysis
We planned sensitivity analyses to measure the effects of including trials at risk of selection bias (inadequate or unclear allocation concealment) or detection bias (inadequate or unclear blinding of outcome assessor). We also planned to assess the presence of small study bias (i.e. intervention effect is more beneficial in smaller studies) in the meta-analysis by comparing the fixed-effect estimate with the random-effects estimate for primary outcomes.

'Summary of findings' tables and assessment of the quality of the evidence
When there is sufficient evidence in future to merit the preparation of summary of findings tables, we will develop these for the main comparisons. We used the GRADE approach to assess the quality of evidence related to each of the key outcomes listed in the types of outcome measures. (17)
The search led to the identification of 18 potentially eligible studies, from which the complete papers were retrieved. A total of four studies, published between 1994 and 2013, were included on the review. (18)(19)(20)(21) Overall, there were four included studies, eight excluded studies and six ongoing studies ( Figure 1).

Included studies
This review was based on four randomized clinical trials: Gotlin et al., (18) Levine et al., (19) Petterson et al. (20) and  (all studies presented in English). These trials were found at PubMed, Cochrane Library and Embase. Included studies details are specified at appendix 2.

Study design
Gotlin et al., (18) Levine et al., (19) Petterson et al. (20) and  were single-center controlled randomized studies. All studies compared two groups undergoing the same interventions (exercises versus exercises and NMES). Gotlin et al. (18) evaluated exercises and continuous passive motion (Control Group) versus exercises, continuous passive motion and NMES (experimental group).

Participants
The four studies included trials totalized 376 participants.

Age and sex
Gotlin et al. (18) described that mean age was 64.8 years in the exercise group (control) and 66.2 years in the NMES plus exercise group (intervention). The Control Group comprised 16 women and 15 men, and the intervention group comprised 20 women and 15 men. In Levine et al., (19) the mean age was 65.1 years in the Control Group, and 68.1 years in the intervention group. The Control Group comprised 21 women and 13 men, and the intervention group was composed of 25 women and 7 men. Petterson et al. (20) reported that the Control Group were composed of 45 woman and 55 were men with mean age of 65.2 years-old. In the intervention group, 47 participants were women and 53 were men, presenting mean age between sexs of 65.3 years-old. In Stevens-Lapsley et al., (21) the sample consisted of 16 women and 15 men in the Control Group and 20 women and 15 men in the intervention group, presenting mean age between sexs of 64.8 years-old for the Control Group and 66.2 years-old for the intervention group.
All participants, in all trials, held a unilateral or bilateral knee osteoarthritis diagnosis. None of the studies described the classification or TKA previous treatment.

Interventions
The included studies were grouped according to the interventions analyzed.
Gotlin et al. (18) analyzed the effects of exercises and continuous passive motion (Control Group) versus exercises, continuous passive motion and NMES (experimental group) in 40 patients. Levine et al. (19) compared a muscle strengthening program and knee ROM gain versus NMES associated only to knee ROM exercises in 70 participants. Petterson et al. (20) and  compared a progressive muscle (quadriceps) strengthening program versus NMES associated with progressive muscle strengthening, both of early start (immediate postoperative), in 266 participants.

Quality of life
Gotlin et al. (18) and Levine et al. (19) did not measure this endpoint. Petterson et al. (20) and  evaluated the quality of life using SF-36.

Treatment failure
All included trials reported no treatment failures.

Range of motion
In Gotlin et al., (18) Petterson et al. (20) and  studies were evaluated through goniometry. Levine et al. (19) also evaluated their participants' knee ROM, but did not report which instrument was used to measure this outcome.

Excluded studies
Eight papers were excluded for not meeting the inclusion criteria. The reasons for exclusion are presented in chart 1.

Ongoing studies
Our search for ongoing studies resulted in 16 papers on Clinical Trials and Current Controlled Trials. Ten studies were excluded for not meeting our inclusion criteria or being irrelevant. We included: ISRCTN89785408, ISRCTN50117467, NCT01096524, NCT01548040, NCT00224913 and NCT01844193 (Appendix 3).

Risk of bias in the included studies
All included trials had methodological flaws, rendering them at moderate risk of bias ( Figure 2).
Concealment of allocation before assignment was not described in any study, preventing its appreciation (unclear).

Blinding (performance bias and detection bias)
All trials were judged to be at high risk of performance and detection bias. As they all compared physical therapy interventions, it was not possible to blind treatment providers. No trials included sham intervention; therefore participants were not blinded. It may have

Incomplete outcome data (attrition bias)
Trials with 80% or more participants completing followup and those whose losses were balanced between intervention groups were deemed as presenting low risk of bias. All included trials (18)(19)(20)(21) were considered as presenting low risk of bias.

Selective report (reporting bias)
Three studies (19)(20)(21) were considered as presenting low risk of bias, since their protocols and pre-specified outcomes were available. On the other hand, Gotlin et al. (18) was considered as high risk of bias, since it did not present a specified protocol.

Additional potential bias sources
Gotlin et al., (18) Petterson et al. (20) and Stevens-Lapsley et al. (21) trials seem to be free from additional biases. Only Levine et al. (19) was considered as high risk of bias, since it not presented a NMES protocol.

Effects of interventions
The included studies evaluated the following outcomes: function or disability, ROM, quality of life and treatment failure. Additional outcomes planned in our protocol were not evaluated due to insufficient data.

Comparison
Neuromuscular electrical stimulation versus exercises (with or without continuous passive motion) starting up to the first postoperative week.

Function or disability
Function measures were analyzed and made available in the following sequence: TUG, 6MW, SCT, quadriceps activation, femoral quadriceps strength, and WOMAC.

Timed Up and Go
In Levine et al., (19) there were no significant differences in both the short-term ( (20) reported no statistically significant difference (p>0.08).

Femoral quadriceps strength (N-m/kg)
Petterson et al. (20) also reported the lack of significant difference between groups (p>0.08). No statistically significant differences between the two groups at the short-term (

Quality of life
The SF-36 questionnaire was used to measure the quality of life during and after the physical therapy intervention in both Petterson et al. (20) and  studies and data were analyzed according to its components.
Petterson et al. (20) used the KOS questionnaire to measure knee function and also reported no statistically significant difference in both short-term and long-term endpoint (p>0.01).

Treatment failure
All included trials reported no treatment failures.

Pain
None of the included studies individually evaluated this outcome.
Petterson et al. (20) report no significant difference between both groups during all months of intervention (p>0.01).

DISCUSSION
At this review, only randomized clinical trials were included, leading to the analysis of four trials deemed of moderate risk of bias and evaluating kinesiotherapic physical therapy interventions compared to NMES with physiotherapy use in 376 participants undergoing TKA.
No evidence indicated if NMES with physiotherapy provided benefits regarding the quality of life. The postoperative treatment with NMES can improve the femoral quadriceps function, but we are not sure about the effectiveness of this intervention, due to the low quality evidence.
Very low evidence from the included trials presented a low general quality resulting from methodological failures, including the lack of allocation concealment and participants and personnel blinding in all trials. However, the quantitative results of this review must be carefully interpreted, requiring confirmation of such data by evidence derived from high methodological quality trials.
We believe that our search strategy was complete, with no language restriction. However, it is possible that we missed some potentially eligible studies. We tried to contact the included studies' authors in order to obtain some data, but with no success.
We found a systematic review comparing NMES versus exercise therapy to treat the quadriceps inhibition after TKA (Monaghan et al). (29) including two randomized and non-randomized clinical trials, and a total of 69 subjects. Our study results are consistent with the Cochrane systematic review results and our conclusion is similar to this publication.
Monaghan et al. (29) evaluated NMES use for quadriceps strengthening pre-and post-TKA and reported no significant differences for these outcomes; however, they considered included studies with a high risk of bias due to study design limitations and presented results imprecision, preventing a meta-analysis performance. The authors concluded that the identified studies do not allow any definition regarding NMES pre-or post-TKA.
Monaghan et al. (29) also interpreted that participants undergoing quadriceps NMES presented a slight advantage in function improvement and less deficiency than those conservatively treated in the short follow-up, just as we see at the clinical practice and consistent with the findings in Gotlin et al. (18) However, efficacy was reduced at the long-term follow-up.
Therefore, this review is inconclusive about NMES efficacy, and further evidence is required to support or deny its use at quadriceps activation after TKA. The authors are aware that this review subject is the object of an ongoing investigation and could be updated in order to incorporate new evidences.

CONCLUSION
The very low evidences from included studies found on this review do not allow any conclusions regarding neuromuscular stimulation application for quadriceps strengthening with physical therapy before or after total knee replacement. Until now, evidence for neuromuscular stimulation use to quadriceps strengthening in this patient group is unclear. However, it is critical that future studies verify the quadriceps strength pre-and post-neuromuscular stimulation using reliable evaluations and validated tools, as well as a clear description of the applied dose in the study design. It is also of uttermost importance that results be presented appropriately for meta-analysis performance. Improved function from progressive strengthening interventions after total knee arthroplasty: a randomized clinical trial with an imbedded prospective cohort.  Intervention time: 6 weeks of intervention with a segment for 12 month post-TKA evaluation (patients were evaluated at the 3 rd and 12 th month by blinded testers) Surgical intervention type: tricompartmental, cemented TKA with a medial parapatellar surgical approach Conservative intervention type: muscle strengthening exercises and NMES Rehabilitation: -Exercises + NMES group: treatment began 3 to 4 weeks after TKA. The progressive strengthening exercises program associated with NMES was performed 2 or 3 times per week, for 6 weeks, totalizing 12 therapy visits. Therapies targeting knee extension and flexion, patellar mobility, quadriceps strength (2 series of 10 repetitions, progressing to 3 series), pain control, and gait training were included in both groups. NMES consisted of 10 electrically elicited contractions of the quadriceps. Patients were seated in an electromechanical dynamometer at 60° of knee flexion. Two self-adhesive electrodes were placed over the rectus femoris muscle belly proximally and the vastus medialis muscle belly distally. Stimulation was characterized by a 2,500Hz, sinusoidal, alternating waveform current at 50 bursts per second, for 10 seconds, plus a 2 second ramp on time, with an 80-second rest period between contractions. Current amplitude was increased to the patient's maximum tolerance -Exercises group: the same protocol mentioned above was used Other co-interventions: not reported

Results
Follow-up period: 1 year follow-up period; participants were evaluated at admission and at 3 and 12 months after TKA Loss at follow-up: 51 participants were lost during the 12-month period: -Exercises group -19 participants were lost in 1 year: -Did not complete treatment: 3 participants  We contacted the authors by e-mail more than once in order to obtain the missing data, but with no response so far

Risk of bias table Bias
Authors appreciation Appreciation support Random sequence generation (selection bias) Unclear The generation sequence was not reported Allocation concealment (selection bias) Unclear The concealment method was not reported Participants and personnel blinding (performance bias) High Participants and personnel were not blinded Outcome evaluation blinding (bias detection) Low Outcome assessors were blinded Incomplete outcome data (attrition bias) Low Outcome data figure-balanced between intervention groups, with similar reasons for lack of data between groups Selective report (reporting biases) Low The study protocol was available and all of the study's pre-specified (primary and secondary) outcomes that are of interest for this review have been reported in the pre-specified way

Other biases Low
The study seems to be free from other biases Acronyms and abbreviations NIH: National Institutes of Health

Appendix 2. Extraction form of the characteristics of the included studies ID do estudo: Stevens-Lapsley et al. (21) (NCT00800254) Interventions
Intervention time: from the first to the third postoperative day (inpatient phase) + 30 days (outpatient phase). Patients were evaluated between 1 and 2 weeks before surgery and at 3, 5, 6, 13, 26 and 52 postoperative weeks by non-blinded study testers Surgical intervention type: unilateral TKA by 3 orthopedists from the University of Colorado. Conservative intervention type: muscle strengthening exercises, stretching, ROM gain and function (gait training); NMES Rehabilitation: -Exercises + NMES group: inpatient rehabilitation started at the first postoperative day with basic exercises twice a day and continued during the 3 days of hospitalization (the exercises protocol was the same for both groups). After hospital discharge, participants received 6 treatments at home for 2 weeks followed by 10 to 12 outpatient visits. Exercises consisted of knee passive range of motion stretching; patellofemoral mobilization (as needed); incision mobility; cycling ROM; lower-extremity flexibility exercises for the quadriceps, calf, and hamstring muscles; modalities (ice or heat as needed); gait training; and functional training for transfers and stair climbing. For strengthening, both weight-bearing and non-weight-bearing exercises were initiated with 2 sets of 10 repetitions and progressed to 3 sets of 10 repetitions according to the patient's tolerance. A portable Empi 300PV stimulator (Empi Inc, DJO Global) was used for the NMES intervention because this device is equivalent to the VersaStim 380 (Electro-Med) found at the university rehabilitation clinic. During current application, patient was sat on a stable chair with the affected lower limb secured by Velcro straps to allow for approximately 85° of hip flexion and 60° of knee flexion. Self-adherent electrodes were also used (7.6x12.7cm). Electrodes were placed on the distal medial and proximal lateral portions of the anterior thigh and marked to ensure consistent reapplication by the participant. A biphasic current with symmetrical waveform, F: 50Hz, 15", 3-second ramp-up time, 45" T-off, 250-microsecond pulse duration was used. Treatment was instituted 48 hours after surgery, twice a day, for 6 weeks. These patients, after randomization to this group, were able to try the current before for adaptation purposes.
-Exercises group: the same protocol mentioned above was used Other co-interventions: not reported

Results
Follow-up period: NMES group: participants will receive specific instruction from a member of the study team on application and logbook recording of the stimulator. The device will be applied to the affected thigh with electrode placement depending on thigh length and girth according to the manufacturer's guidelines. They will also receive written instruction on the device controls and the NMES training program schedule. All NMES sessions will be performed with the subject sitting with their knee flexed to 60 degrees. Wooden strips joined with a 60 degrees bend will be provided to all subjects to assist with positioning throughout the program. They will sit with their feet flat on the ground and their toes against a wall to prevent knee extension caused by the resulting quadriceps contractions, and thus permit isometric training 5 sessions per week (Monday to Friday) for 6 weeks 20 minutes in duration. Participants will be instructed to use the device early in the morning, between 8 and 10 a.m., to minimize muscle fatigue that may occur after normal daily activities. A student from Dublin City University will attend the participants' home on day 8 to ensure the subject is using the device appropriately as well as adhering to the protocol. Telephone communication will occur weekly, on Fridays, with each subject in the intervention group to ensure they are adhering to the protocol. The stimulator has a built-in log that records the total number of completed sessions, total treatment time, and average intensities reached for each channel for the previous 4 sessions. We will document these readings at weeks 2, 4, and 6 Control Group: subjects assigned to the Control Group will receive standard care. They will attend DCU at baseline, and weeks 3, 6, and 12 for quadriceps strength assessments. All functional and clinical evaluations, as well as MRI scanning, self-report questionnaires and muscle biopsies will be performed as in the intervention (NMES) group. They will also receive weekly telecommunication to answer any questions they may have in relation to the study

Results
Primary outcomes: who are walking independently with or without assistive devices; must be able and willing to complete all study assessments and to be followed for the full course of the study; must be able to read, write and follow instructions in English; must be able and willing to provide informed consent; must be willing and able to attend for preoperative assessment Exclusion criteria: individuals who have failed the preoperative assessment; individuals with a history of foot and/or ankle pathology; individuals with a history of tibial or femoral fractures; individuals with a history of underlying neurological conditions; individuals with physical conditions which would make them unable to perform study procedures; individuals with a total hip replacement; individuals undergoing revision TKA of the same operated leg; pregnant women or inadequate precautions to prevent pregnancy; diagnosis of a medical condition that would contraindicate treatment with the product, e.g. skin lesions at electrode site; individuals with an active implanted medical device (i.e. pacemaker, pump); individuals with a history of stroke; individuals with a history of neurological disorder that affects lower extremity function (stroke, peripheral neuropathy, Parkinson's disease, multiple sclerosis etc.); individuals with a diagnosis of inflammatory arthritis (including rheumatoid arthritis, gout or psoriatic arthritis); individuals with muscle disease (i.e. muscular dystrophy); visible skin injury or disease on their legs; principal investigator for this study, or member of study staff Interventions NMES group: Kneehab TM on the quadriceps of the affected leg, 20 minutes, twice per day, 5 days per week, over 12-week intervention (6 weeks before surgery, 6 weeks after surgery) Control Group: the Control Group will complete the standard physiotherapy care pre-and post-TKA surgery without NMES

Results
Primary outcomes: -Quadriceps activation -Quadriceps muscle strength ( Inclusion criteria: individuals who are scheduled for TKA surgery with the Smith and Nephew Visionaire prosthesis and anterior surgical approach; individuals who are at least 40 years of age; individuals with a BMI <40kg/m 2 ; individuals who are walking independently with or without assistive devices; individuals with a Short Performance Battery Score >7; must be able and willing to complete all study assessments and to be followed for the full course of the study; must be able to read, write and follow instructions in English; must be able and willing to provide informed consent; must be willing and able to attend the additional preoperative assessment Exclusion criteria: individuals with a history of foot and/or ankle pathology; individuals with a history of tibial or femoral fractures; individuals with a history of any underlying neurological conditions; individuals with physical conditions which would make them unable to perform study procedures; individuals with a total hip replacement; individuals undergoing revision TKA of the same operated leg; individuals who are pregnant; individuals diagnosed with a medical condition that would contraindicate treatment with the product, e.g. skin lesions at electrode site; individuals with an active implanted medical device (i.e. pacemaker, pump); individuals with a history of stroke; individuals with a history of neurological disorder that affects lower extremity function (stroke, peripheral neuropathy, Parkinson's disease, multiple sclerosis etc.); individuals with a diagnosis of inflammatory arthritis (rheumatoid arthritis, gout or psoriatic arthritis); individuals with muscle diseases (i.e. muscular dystrophy); individuals with visible skin injury or disease on their legs; individuals who have been committed to an institution by virtue of an order issued either by the courts or by an authority Interventions Kneehab TM group: NMES using Kneehab XP on the affected leg, 20 minutes, twice per day, 5 days a week. Subjects will begin use of the device at 6 weeks preoperatively and continue through 6 weeks postoperatively Control Group (TENS): quadriceps TENS (at a minimal sensory input) using Kneehab XP on the affected leg, 20 minutes, twice per days, 5 days a week. Subjects will begin use of the device at 6 weeks preoperatively and continue through 6 weeks postoperatively Outcomes