MRI Reflects Articular Cartilage Degeneration Caused By Proteoglycan Depletion In The Rabbit Knee

Objective To study the feasibility and appearances of MRI to detect the early stages of cartilage degeneration and its valuesMethods Intra-articular injection of 5 units of papain causing a reversible loss of cartilage proteoglycan in the newzeland rabbit knees. Rabbits were scanned with magnetic resonance imaging,using a 0.3T hitachi magnet with 16cm coil.grdient echo sequences were performed in the sagittal planes at 0,24,48,and 72h after intra-injection of papain, signal intensity and thickness of cartilage were measured. The proteoglycan content was measured biochemically and histochemically.Results The cartilage thickness and signal intensity decreased significantly in treated knees as compared with in control knees at 24 and 48 hours (P < 0.05 ) , but resumed at 72 hours ( P > 0.05 ) after injection of papain. These changes on MR images were consistent with the changes of proteoglycan concentration measured by biochemical analysis and histochemical staining of cartilage.Conclusion The reduced thickness and signal intensity of cartilage on MR images corresponded to the loss of cartilage proteoglycan, indicating that it is possible for MRI to detect the early stages of cartilage degeneration.