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.

The study duration will be until 12 weeks ± 1 week postoperatively. Data will be collected (1) 4 weeks preoperatively, (2) prior to hospital admission for TKA, and (3) at 3, 6, and 12 weeks postoperatively. The research coordinator at the site will identify, recruit, and prospectively follow the 66 patients at his/her site.

All data will be entered and maintained in REDCap, an electronic data capture tools hosted at Cleveland Clinic. REDCap (Research Electronic Data Capture) is a secure, web-based application designed to support data capture for research studies, providing 1) an intuitive interface for validated data entry; 2) audit trails for tracking data manipulation and export procedures; 3) automated export procedures for seamless data downloads to common statistical packages; and 4) procedures for importing data from external sources. Only members of the study team (i.e. the personnel listed on the institutional review board (IRB) application) will have access to protected health information of patients included in this study.

Pretreatment Assessments

Before treatment, the following assessments/tests will be performed and the results will be recorded on the appropriate pages of the (case report form) CRF, and or Microsoft excel, Microsoft Word, and REDCap:

• Informed consent
• Age, gender, height/weight/(body mass index) BMI
• Concomitant diseases
• Physical examination
• Baseline range of motion of affected knee
• Baseline timed up and go test (TUG test, detailed in Appendix A and as described by Podsiadlo et al.)
• Baseline Stair Climb test
• Baseline QFM strength
• Baseline Modified Knee Injury and Osteoarthritis Outcome Score (KOOS) and Veterans Rand 12(VR-12) assessments
• Baseline VAS (visual analog scale)pain score
• Current medications
• Any use of ambulation assist device

Presurgery Assessments

Before surgery, the following assessments/tests will be performed and the results will be recorded on the appropriate pages of the CRF, and or Microsoft excel, Microsoft Word, and REDCap:

• Device usage patterns (thru app for preop NMES group)
• Range of motion of affected knee
• TUG test
• Stair Climb test
• QFM strength
• Modified KOOS and VR-12 assessments
• VAS pain score
• Current medications
• Activity levels using Misfit Wearables® fitness monitor will be uploaded and incorporated into online app

Operative Assessments

The following will be collected from the Operative and Anesthesia Records and recorded on the appropriate pages of the CRF, and or Microsoft excel, Microsoft Word, and REDCap:

• Surgeon name
• Approach used
• Randomization assignment
• Diagnosis
• Length of surgery
• Estimated blood loss
• Type of anesthesia
• Implant type

Postoperative Assessments After surgery, one or more of the following will be collected through the online app and at follow-up visits.

• Device usage patterns (thru app)
• Range of motion of affected knee (thru app and at follow-up)
• TUG test
• Stair Climb test
• QFM strength
• Modified KOOS and VR-12 assessments
• VAS pain score
• Length of stay (hospital, extended care facility)
• 90 day readmission rate
• Discharge Disposition (home vs skilled nursing facility vs inpatient rehabilitation)
• Patient Satisfaction measures
• Any use of an ambulation assist aid
• Activity levels using Misfit Wearables® fitness monitor will be uploaded and incorporated into online app

As a last resort, if a patient is unable to keep one of these appointments, he/she will be either be mailed or emailed the patient reported outcome forms so the patient can fill them out. The patient will date and time the forms. Participants will then send the form back in a pre-addressed envelope. The patients email will be verified by the patient during a clinical visit to ensure accuracy of the correct recipient. Patients not responding to the initial mailer will be contacted by phone and forms may be administered over the phone. The mailers and/or phone calls will allow us to collect all data except the physical function measures.

All data will be entered and maintained in Redcap

Inclusion Criteria:

1. Patients undergoing unilateral primary total knee arthroplasty
2. Patients who are between the ages of 18 - 85 years
3. Patient has signed informed consent
4. Patient has access to a smartphone or tablet (Android or iOS)

Exclusion Criteria:

1. BMI ≥ 40
2. Inflammatory arthritis
3. Patients who are expected to be in extended care facilities after surgery
4. Patients who have used an at-home NMES device in the past
5. Preoperative daily use of narcotics (i.e., high tolerance)
6. Already enrolled in another research study, including the present study for contralateral knee
7. Other lower-extremity orthopaedic conditions which could interfere with limb function, especially those with significant pain requiring daily analgesic intake
8. Patients with concurrent abdominal, inguinal or femoral hernias
9. Cutaneous lesions in areas of electrode pad placement
10. Patients with a history of epilepsy
11. Patients with a cardiac pacemaker/defibrillator
12. Allergy to adhesives
13. Inability to meet follow-up visits required for the study
14. Patients who are a risk for poor compliance or have a poor understanding of the use of the NMES device
15. Condition deemed by physician or medical staff to be non-conducive to patient's ability to complete the study, or a potential risk to the patient's health and well-being

Adverse event data were collected through 12 weeks postoperative.