Osteoarthritis is the most common joint disease affecting the elderly and consists of a group of clinically heterogeneous disorders characterized by hyaline cartilage loss and subchondral bone reaction that cause debilating pain and a reduced ability to work. As OA structural changes take place over decades in humans, it is understandably difficult to study the changes observed in the early stages of the disease. Thus, animal models that can reproduce the morphological and molecular changes in OA have been extensively used to study the pathophysiology of the disease. As the knee is one of the joints most commonly affected by OA, the surgically-induced OA model – which excises the medial collateral ligament.

Moreover, three DMOADs applied in this surgically-induced model have displayed similar effects in the knees of OA patients. Although there have been multiple studies reporting on OA development after knee destabilization with different endpoints and visualization methods, MRI findings have not yet been correlated with the macroscopic progress of OA in this surgically-induced OA rabbit model, and the timepoint of disease status in this OA model has not yet been defined. In order to accomplish this task, selection of an appropriate imaging modality is paramount. Although radiological joint space narrowing by X-ray radiography is the “gold standard” for assessing OA, there is currently no well-established imaging modality to visualize changes in chondral and subchondral tissue in order to correlate these changes with more commonly utilized histolopathologic analysis and molecular biomarkers. To this end, the superior soft-tissue contrast and multiplanar capabilities of magnetic resonance imagaing appear to make it the ideal technique for providing precise and reliable semi-quantitative information on changes in chondral and subchondral tissue structure. Therefore, in this study, MRI of a surgically-induced OA rabbit model was used to assess changes in osteophytic, chondral, and subchondral structures over a period of eight weeks in order to correlate these MRI findings with the macroscopic progress of OA.

The severity of cartilage lesions, osteophytic growth, and subchondral bone edema were evaluated using semi-quantitative scoring systems in order to define the timepoint for disease status in this OA model. Several recent publications have PR-171 described the use of fat suppressed three dimensional spoil gradient-recalled sequences for the evaluation of knee hyaline cartilage, which has shown greater sensitivity and specificity in detecting hyaline cartilaginous defects. However, these sequences generally require long acquisition times and additional time for off-line manipulation to create images. Animals can produce motion artifacts during long acquisition periods that adversely affect MRI quality.We hypothesized MaR1 to possess similar properties.