Evaluation of NMES Therapy for Pain Relief Associated With Knee Osteoarthritis

Inclusion Criteria: 1. Subject must provide a signed informed consent for CM-2019R. The subject will be provided with a copy of the signed Informed Consent upon signature. 2. Currently enrolled in the parent trial CM-2019 or have successfully completed the parent trial within 21 days of enrollment in the roll-over trial. 3. Willing and able to continue parent trial study treatment. 4. Pregnancy test, if it has been \>14 days since completion of the parent trial. 5. Subject must continue to be willing to refrain from receiving knee intra-articular injections of steroids, knee intra-articular injections of hyaluronic acid, opioids, and analgesics (except for acetaminophen up to 3000 mg/day or an equivalent) for the duration of the study. 6. Subject must continue to be willing to take acetaminophen (up to 3000 mg/day) or an equivalent as pain medication for the duration of the study. 7. Subject must continue to be willing to stop taking any pain medications 24 hours prior any scheduled study visit. 8. Subject must continue to be willing to stop receiving knee physical therapy of the target knee for the duration of the study. 9. Subject must continue be willing to stop wearing any knee unloader brace of the target knee for the duration of the study. 10. Subjects must be willing and able to comply with all study procedures for the duration of the clinical study Exclusion Criteria: 1. Subjects with a new diagnosis of inflammatory arthritis (knee rheumatoid arthritis, active gout, knee joint infection, Lyme disease, SLE, etc.) since parent trial enrollment. 2. Subjects with a new diagnosis of severe neuropathy condition and under medication for treatment of the condition since parent trial enrollment. 3. Subjects with a new diagnosis of fibromyalgia since parent trial enrollment. 4. Subjects who have had an injury or an acute traumatic injury to the target knee since parent trial enrollment. 5. Subject must NOT have had arthroscopy of the target knee since parent trial enrollment. 6. Subjects who have had treatment of the target knee with intra-articular injections of steroids since parent trial enrollment. Subjects who have had intra-articular injections of hyaluronic acid since parent trial enrollment. 7. Subjects who have a scheduled surgery on the target knee within the study period. (Subjects that are contemplating the surgery can be included.) 8. Subjects who have used electrotherapy or acupuncture for OA of the target knee since parent trial enrollment year. 9. Subjects who have had implanted electrical devices since parent trial enrollment (cardiac pacemakers, deep brain stimulators, implantable cardiac defibrillators). 10. Subjects with a current new malignancy or who have received treatment for malignancy since parent trial enrollment, with the exception of resected basal cell carcinoma and squamous cell carcinoma of the skin. 11. Subjects with a new skin breakdown or infection in the area where the study device will be placed (quadriceps of the target knee). 12. Subjects with any newly reported chronic conditions (e.g., diabetes, hypertension, congestive heart failure, etc.) or that have not been well-controlled during the parent trial. 13. Subjects who have any new litigation for worker's compensation. 14. Subjects with any new condition, in the opinion of the Investigator that might interfere with the evaluation of the study objectives. 15. Subjects who are pregnant. 16. Subject who enrolled in any new clinical study from the last day of treatment in the parent trial that required the use of an investigational device, drug or biologic.