Prospective Assessment of the Efficacy of Hyaluronate Knee Injections in Patients With Osteoarthritis

Inclusion Criteria: * age 45-90 * seeking medical care for painful knee osteoarthritis * alignment based on AP standing radiographs of neutral to 10º of valgus * no prior surgery on the ipsilateral knee * no history of major trauma to either knee or either hip * no history of congenital hip dysplasia * No history of inflammatory synovitis or crystalline arthropathy * No history of systemic rheumatic disease * cruciate and collateral ligament stability, defined by clinical examination * meniscus intact (MRI grade II degenerative signal acceptable) * Noyes compartment score: no greater than 50% of cartilage thickness over an area greater than 15mm * If bilateral OA, the most painful knee, (as documented by VAS scale for pain) which qualifies for the study will be entered. * If taking glucosamine chondroitin sulfate, discontinue at least one month prior to HA injections Exclusion Criteria: * previous IA HA injection in the ipsilateral knee * IA steroid in the ipsilateral knee in the past 3 months * MR evidence of inflammatory or hypertrophic synovitis * Large joint effusion with a ballotable patella on baseline clinical exam * Inability to safely perform MR imaging * Active systemic infection * Active malignancy (except non-melanomatous skin cancer) * Allergies to HA or chicken products * Clinical symptoms of an acute meniscal tear (locking, new acute mechanical symptoms etc…) * A recent injury to the knee * Radiographic evidence of Grade III or IV Kellgren and Lawrence OA * Chondrocalcinosis on radiographs * Unwilling to discontinue or avoid glucosamine chondroitin sulfate for the 12 month study period * People taking blood thinners or who have bleeding problems * Anticipated lower extremity surgery during the next 12 months * BMI \>30 kg/m2