Identification of early knee osteoarthritis - a new horizon

Knee osteoarthritis (OA) is a common and significant cause of disability. Until recently, the major investigation to help establish a diagnosis of knee OA was the joint radiograph. This imaging modality offers only a two-dimensional image of a three-dimensional structure, and can only crudely identify major joint abnormalities at the later stage of disease. Moreover, joint radiographs cannot fully characterise subtle changes in intra and extraarticular structures, such as cartilage and bone marrow abnormalities that are now considered to be part of a whole-organ disease process. The recent advent of Magnetic Resonance Imaging (MRI) has enabled a three-dimensional assessment of the entire joint, thus providing new insights into the natural history of joint arthropathies. It is likely that morphological changes in articular structures caused by the OA process have their origins in the apparently healthy asymptomatic knee joint. MRI has therefore enabled the opportunity to better examine and understand pre-clinical and very subtle early aberrations in joint morphology, prior to the onset of radiographic disease. This discussion seeks to explore knee OA as a disease entity that can be recognised before any radiographic change. This may pose new, yet exciting challenges for the identification and classification of disease, and provide a better understand of the pathogenesis of knee OA.