Stimulation of Peripheral Afferents to Reduce Muscle Inhibition at the Knee

Knee osteoarthritis is a leading cause of disability, and the muscle weakness that limits walking in this population arises not only from the joint itself but from afferent signals that inhibit motor drive to the thigh muscle, which is why exercise alone so often produces incomplete recovery. This project examines whether brief, non-invasive electrical stimulation of a nerve behind the knee can reduce inhibition and restore muscle coordination while walking in adults with knee osteoarthritis. Establishing this effect would identify a modifiable neural target that current rehabilitation does not address, with the potential to improve physical function and independence for the millions of adults living with this condition.

Inclusion Criteria: * \>45 years old * Able to speak and understand English * Unilateral or bilateral knee OA, per NICE criteria * Age 45+ AND * Have activity-related joint pain AND * Have either no morning joint-related stiffness or morning stiffness that lasts no longer than 30 minutes * Score \> 3/20 on WOMAC pain scale * If using pain medications, report \>4 weeks of stable use without recent adjustments Exclusion Criteria: * History of lower extremity surgery. * BMI \> 40kg/m\^2 * Received an intra-articular knee joint injection within the last 3 months. * Currently pregnant. * Currently experiencing heavy menstruation, within one month of an IUD contraceptive device (e.g. coil) being fitted or within 6 weeks after giving birth or at least three months after having a Caesarean. * Suspected or diagnosed heart problems (e.g. arrhythmia, cardiac disturbances). * Use of an implanted electronic device (e.g. a cardiac pacemaker or defibrillator). * Insulin-dependent diabetes. * Implants in the lower limb. * Suspected or diagnosed epilepsy or a familial history of epilepsy. * History of neurologic or psychiatric condition (e.g. Parkinson's disease, bipolar disorder, epilepsy, etc) * Implanted cardiac pacemaker, cochlear implant, medication pump, surgical clips or other metal (dental implants excluded). * Use of alcohol or recreational drugs in the prior 12 hours. * Frequent or severe headaches. * Prior adverse reaction to transcranial magnetic stimulation. * Altered sensation (hypo or hypersensitivity) of the skin of the thigh. * Swollen, infected, inflamed, or damaged skin of the thigh. * Current Use of prescription and over the counter medications will be grounds for exclusion except for: * Contraceptive (birth control) drugs (e.g. those containing ethinyl estradiol and/or norethindrone). * Seasonal allergy medications (e.g. cetirizine (Zyrtec), fexofenadine (Allegra), and loratadine (Claritin)). * Antihypertensives * Statins * GLP-1 agonists * Non-insulin diabetes medications (metformin) * Thyroid medications * Osteoporosis medications * Respiratory medications * Pain medications available over the counter (ibuprofen, acetaminophen, etc)