Prediction of Response to Intra-articular Injections of Hyaluronic Acid for Knee Osteoarthritis

Background Osteoarthritis (OA) of the knee is a debilitating condition that affects an estimated 21 million Americans. This number is expected to rise steadily as the population ages. The medical expenditures associated with arthritis and other rheumatic conditions in the United States have increased from $50 billion in 1997 to $86 billion in 2003. In 2003, almost 420,000 total knee replacements were performed, primarily for arthritis. Injections of hyaluronic acid (HA) have been shown to provide symptom relief for many OA patients who have failed to respond to conservative interventions. Many other patients, however, experience only slight or no improvement. The results from this study will allow physicians to identify whether a patient is likely or not likely to respond well to HA therapy leading to improved treatment success rates.

Goals This study has two related goals: 1) to identify patient and treatment factors that predict response to intra-articular injections of hyaluronic acid for knee osteoarthritis using multivariable analysis and 2) develop mathematical and statistical models that will predict individual patient response to HA for knee OA.

It is anticipated that the investigators will develop computer software in this study that can support clinical decision making related to viscosupplementation in the treatment of knee OA. If this project yields successful patient predictive models, physicians who are considering a trial of HA for a patient will have some empirical basis for treatment selection. Eventually a physician would be able to assess a relatively small number of variables for a patient and then be provided with predictions regarding treatment response.

**Please note that the study site at the Naval Medical Center in Portsmouth, Virginia can only enroll patients who are eligible to be treated at a military facility.

Inclusion criteria

• Symptomatic knee osteoarthritis presenting to physician's office
• Radiographic evidence of knee osteoarthritis
• Age 18 years or older
• Failed minimum of 3 months of non-operative treatment, including, but not limited to, Tylenol, anti-inflammatory medication, cortisone injection, physical therapy, bracing, and/or heel wedge
• Symptoms for at least 3 months

Exclusion criteria

• Associated ligamentous instability
• History of deep knee infection
• Candidate for total knee arthroplasty or arthroscopy
• Peripheral neuropathy.
• X-rays that are completely negative and only MRI evidence or arthroscopic evidence (from previous arthroscopy) of OA.
• Prior HA injections at any point in the past
• Chondrocalcinosis
• Patients with precautions or contraindications for viscosupplementation use
• Cortisone injection within past 3 months