To Look at the Characteristics of Synovial Fluid and Cartilage Matrix in Osteoarthritic Knee After Hyaluronic Acid Injection

The purpose of this study is to identify novel imaging markers for characterizing the biochemical profiles in synovial fluid and cartilage matrix in OA knee joints after intra-articular HA (Euflexxa) injection using high field NMR and MRI techniques. We hypothesize that: 1. High-field HRMAS NMR spectroscopy will provide sensitive measures for biochemical changes within knee synovial fluid after HA injection; 2. Baseline HRMAS spectroscopy, in particular N-acetyl peaks, as well as early changes of glutamate will predict patient response of pain relief after HA injection; 3. MR cartilage T1p and T2 quantifications will provide sensitive measures for biochemical changes within knee cartilage matrix after HA injection. Specifically cartilage T1p and T2 will decrease in patients who respond to the treatment, indicating potential beneficial effects of HA injection to cartilage preservation.