CHECKing radiographic joint damage in early osteoarthritis

Osteoarthritis Osteoarthritis (OA) is the most common joint disease, characterized by pain and functional disability. OA commonly involves the larger joints, with symptomatic knee and hip OA affecting 6% and 3% of the adult population (age 30 years and over), respectively. The prevalence and disease duration will increase in the coming years since known risk factors for OA (ageing and obesity) are increasing in the community. Evaluation of radiographs The symptoms of OA are assumed to originate from structural changes of all tissues of the joint, consisting of cartilage degeneration, osteophyte formation, subchondral sclerosis (increased bone density), synovial inflammation, and soft tissue affection. In clinical practice however, an inconsistent association between structural changes and symptoms hampers the diagnosis of OA. Despite this inconsistency, radiography is the gold standard to detect structural changes since image acquisition is non-invasive, cheap, fast, and generally available. A drawback of the common method to evaluate radiographs (Kellgren & Lawrence grading) is that it provides a summary grade (0-IV) for the whole joint, which has low sensitivity to (subtle) change and assumes a fixed sequence in the development of OA characteristics. Separate quantitative features By evaluating separate radiographic features the existence of such a sequence can be evaluated. Furthermore, more detailed evaluation of radiographs is enabled when quantitative measurement is applied (instead of qualitative grading). Therefore, Knee Images Digital Analysis (KIDA) was developed, which (semi-) automatically measures joint space width (JSW), varus angle, osteophyte area, eminence height, and bone density. Early osteoarthritis For better understanding of OA and for developing adequate preventive treatment, focus needs to shift to individuals at high risk or with early disease, in which structural changes are still absent. Therefore, the Cohort Hip & Cohort Knee (CHECK) was initiated, in which individuals with early complaints of hip and/or knee OA were included who are expected to develop OA in the following years. This thesis This thesis aimed at improving the insight in onset and development of radiographic joint damage due to OA early in the disease. Separate features of knee OA are quantitatively measured by KIDA in CHECK participants. The challenges in measurement of separate features are evaluated, and also the value of these measurements for application in clinical practice and in detecting a relation between damage and symptoms. Conclusions The use of standardized outcome measures of OA is important in evaluating radiographic damage and in finding an association between radiographic and clinical characteristics. Proper image acquisition is of major importance to utilize the surplus value of KIDA, specifically in an early phase of OA. The measurement of separate features can be applied in clinical practice to evaluate radiographic changes in more detail, even in very early OA. Specific radiographic features are identified that are related to clinical outcome, and that are predictors of onset of radiographic OA. Based on measurements of separate features phenotypes of radiographic progression are identified, which is valuable in developing more targeted treatment