Thomas Baum, Jan S. Bauer, Gabby B. Joseph and Thomas M. Link

Institut für Radiologie, Klinikum rechts der Isar, Technische Universität München, Ismaninger Str. 22, 81675 München, Germany

Abstract:

Osteoarthritis (OA) is the most common form of arthritis and one of the leading causes of disability in the elderly. OA is characterized by progressive loss of hyaline articular cartilage. The most commonly affected joint is the knee. The initial stages of OA include proteoglycan loss, increased water content, and deterioration of the collagen network. Magnetic resonance imaging (MRI) based cartilage T2 relaxation times are affected by these pathophysiological processes. Therefore, investigators adopted knee cartilage T2 measurements in clinical studies and hypothesized that T2 can be used as non-invasive diagnostic tool for early stages of knee cartilage degeneration and assessment of therapy response, e.g. after cartilage repair procedures or drug medication. Due to promising results of pilot studies, T2 relaxation time measurements were included in the National Institutes of Health (NIH) sponsored Osteoarthritis Initiative (OAI), a longitudinal, observational multicenter study with 4796 participants. In our studies mainly performed with data of the OAI, we demonstrated that T2 relaxation time measurements were significantly increased in subjects with compared to those without cartilage lesions as assessed by the whole organ MRI score (WORMS). Furthermore, subjects with OA risk factors such as overweight/obesity showed significantly greater cartilage T2 values than normal controls. We also found elevated T2 relaxation times in subjects with versus without knee pain. In our latest study, we observed that increased cartilage T2 at baseline predicted longitudinal morphologic degeneration in the cartilage, meniscus, and bone marrow over three years. In conclusion, MRI based cartilage T2 relaxation time measurements may be suitable as noninvasive biomarker for early stages of knee OA and therapy monitoring.