Use of Quantitative Magnetic Resonance Imaging in the Cross-Sectional and Longitudinal Evaluation of Structural Changes in Knee Osteoarthritis Patients

Assessment of structural damage of the articular cartilage is important for monitoring the progression of osteoarthritis (OA) and evaluating therapeutic response. For many years, clinical studies of drug interventions on symptomatic knee OA have focused mainly on clinical parameters, such as pain and joint function, using self-administered questionnaires but without assessing the effect of treatment on structural changes caused by the disease and the role of treatment in preventing cartilage degradation. Recently, such attempts were made to evaluate cartilage damage and its progression in OA. Serial radiographs of affected joints have appeared as a logical means of documenting the progression of OA over time, providing that a validated, reliable, and easily reproducible technique is used [1]. Improvements in the standardization and interpretation of radiographs have enhanced the reliability of the measurement of the joint space width (JSW) and the evaluation of the joint space narrowing (JSN) [2, 3]. However, the sensitivity to change of this measurement is such that a minimum follow-up of 2 to 3 years and more and large numbers of patients (at least 1500 for a two-arm study) is necessary to establish an effect of pharmacological interventions on OA progression. Moreover, measurement of JSW does not capture information on the cartilage changes alone but is also dependent on the integrity of surrounding tissues, especially the meniscus and the subchondral bone. For instance, enucleation of the knee medial meniscus, which may occur during longitudinal studies, can dramatically change the JSW and affect the reliability of such measurement [4], potentially impairing its use in the assessment of cartilage degradation over time. Finally, the JSW progression provides only one measurement