Imaging Water Mobility of Cartilage in Juvenile Rheumatoid Arthritis

Magnetic Resonance Imaging (MRI) has been utilized in inflammatory arthritis as a tool to detect morphologic or structural abnormalities within joints. Proton (1H) T2 relaxation time measured by MRI is largely a function of water mobility and as such provides information about the physiologic state of the tissue in question (Figure 1). In arthritis of multiple causes, damage to articular cartilage is a critical result of the pathologic process, as advanced damage is often irreversible and predictive of functional difficulty and pain. Water mobility is largely a function of proteoglycan distribution within articular cartilage. We have demonstrated in adult articular cartilage that 1H T2 relaxation time varies spatially in a pattern inverse to the known concentration of proteoglycan.

MSK

Juvenile rheumatoid arthritis (JRA) is an inflammatory arthritis of childhood in which structural damage to articular cartilage occurs and has long term functional implications. Proteoglycan depletion is a known consequence of inflammatory arthritis and may be an important predisposing factor for further articular cartilage degeneration.

We are investigating the measurement of 1H T2 relaxation as a means to assess alterations in articular cartilage water mobility in the knee joint of patients with JRA. It is expected that proteoglycan depletion will result in increased water mobility and thus increased 1H T2 relaxation time. Our hypothesis is that changes in water mobility can be observed in MRI T2 relaxation measurements of articular cartilage early in the course of disease, before irreversible degeneration occurs.

MSK

Representative 1H T2 relaxation profiles within articular cartilage in normal children at various stages of development will be established and used as a means to assess the changes in JRA patients (Figure 2). The detection of biochemical changes in articular cartilage prior to the onset of structural changes may be important in understanding the pathophysiology of articular cartilage damage and may have implications for aggressive treatment.

The investigation of physiologic changes in articular cartilage with degeneration in JRA has implications for patients with arthritis of multiple etiologies, including adult rheumatoid arthritis and osteoarthritis. With the future prospects of chondroprotection and even cartilage transplantation, the delineation of a noninvasive means of assessing early articular cartilage degeneration is very important.