Immediate Effects of rTMS on Excitability of the Quadriceps With Knee Osteoarthritis

The purpose of the study is to identify things that influence the ability to "turn on" the thigh muscle (quadriceps). The thigh muscle tends to be under active with knee osteoarthritis, which may make it difficult to strengthen the muscle. The investigators are also testing a new technology called repetitive transcranial magnetic stimulation (rTMS) to determine whether it may help "turn up" activity in the under active thigh muscle immediately after its application. rTMS uses a targeted pulsed magnetic field, similar to what is used in an MRI (magnetic resonance imaging) machine to send an electrical signal from the brain to the thigh muscle.

The investigators will recruit up to 20 people with symptomatic knee osteoarthritis. The 20 eligible participants will attend 3 sessions in the laboratory. Session 1 is to collect data for Aim 1. Sessions 2 and 3 will include the rTMS interventions and data collection for Aim 2.

Aim 1 is a descriptive study to compare the neural (cortical and corticospinal) excitability of the quadriceps in the symptomatic knee to the asymptomatic knee in participants with knee osteoarthritis. The investigators will examine the associations between neural excitability and clinical measures of pain, strength, function, and coping styles.

Aim 2 is a double blind, crossover study design. Each participant will partake in two testing sessions, spaced 1 week apart. The investigators will evaluate outcome measures prior to and following the "true" intervention versus the "sham" intervention. The true intervention is rTMS + exercise. The sham is sham rTMS + exercise. The primary outcome measures are quadriceps strength, as measured from a maximal isometric voluntary contraction, and quadriceps central activation ratio (CAR), as calculated from the torque values from the voluntary strength measurement and a brief, intense electrical stimulus. Secondary measures evaluate effects of the intervention on 1) clinical measures of pain and functional performance, 2) corticospinal excitability, and 3) intracortical inhibition and facilitation.

Eligibility Criteria:
Inclusion Criteria:

* symptomatic knee osteoarthritis primarily involving one leg based on Western Ontario and McMaster Universities Arthritis Index (WOMAC) function subscale score \> 10 (out of 100 points, indicating most dysfunction)
* diagnosis of knee osteoarthritis
* opposite knee with WOMAC pain score ≤ 5.
* opposite knee does not have a diagnosis of knee osteoarthritis

Exclusion Criteria:

* conditions affecting the leg other than osteoarthritis
* low blood pressure (\< 90 systolic, 60 diastolic) or heart rate (\< 60 beats per minute)
* conditions that limit exercise tolerance such as a heart condition
* pregnant or planning to become pregnant in the next 3 months
* conditions that alter sensation and pain processing
* BMI \> 35
* severe arthritis in both knees
* history of leg or back surgery in the past year or knee replacement surgery;
* injection in the knee joint in the past 4 weeks
* requires an assistive device to walk
* any contraindications for TMS or rTMS (seizures, metal implants in head, brain related conditions, brain injury, drug or alcohol withdrawal)
* medications that lower seizure threshold
* history of fainting spells (syncope) or low blood pressure
* sleep deprived
* inability to understand and repeat back directions regarding the study