Ultrasound (US)-Guided Versus Sham Ultrasound Corticosteroid (CS) Knee Injections

Inclusion Criteria: * Age between 40 and 89. * Meet the American College of Rheumatology criteria for knee OA with knee pain, aching or stiffness on most of the past 30 days and have evidence on radiograph of a definite osteophyte. * Have a pain score of at least 4 out of 10 on an 11 point numeric rating scale. * For participants with bilateral knee OA, the most symptomatic knee will be considered the study knee. If both knees are symptomatic, the subject will choose the one they want treated. * Be able to speak and understand English. * Have a telephone. Exclusion Criteria: * Prior hyaluronic acid injection. * Scheduled knee hyaluronic acid injections, arthroscopy, or knee surgery. * Comorbid conditions including: known other causes of arthritis (infectious arthritis, rheumatoid arthritis, connective tissue disease, gout, pseudogout, or psoriatic arthritis), bony or soft tissue malignancy or skin lesions or peripheral neuropathy involving the lower extremities, cardiopulmonary disease which limits walking more than knee pain, knee instability defined as report of knee buckling or locking within the past month of the study knee, major neurologic deficit that affects gait, psychiatric illness that limits informed consent * Current involvement in litigation or receiving workmen's compensation. These patients are to be excluded because they are expected to bias results. This group will be expected to over-report pain symptoms. This bias cannot be corrected for in the analysis. * Contraindications to intra-articular injections: known bleeding disorder/diathesis. * Prosthesis in the painful knee. * Bilateral total knee replacements. * Pregnancy if no recent knee x-rays are available. * Wheelchair bound. * BMI greater than 40.