Magnetic resonance evaluation of the interrelationship between articular cartilage and trabecular bone of the osteoarthritic knee.

OBJECTIVE: To use high-resolution magnetic resonance imaging (MRI) to determine the relationship between articular cartilage degeneration and trabecular bone changes of the femur, condyles and tibia in human knees with osteoarthritis (OA).
METHODS: Subjects were divided into three groups: without OA (OA0), mild OA (OA1) and severe OA (OA2). Sagittal images of the knee (0.234 x 0.234mm2, 2-mm slice thickness) were obtained at 1.5T and used for calculating the volume and thickness of the femoral and tibial cartilage. Axial images (0.195 x 0.195mm2, 1-mm slice thickness) were used for calculating the trabecular bone structure parameters: apparent bone volume fraction, trabecular number, trabecular separation and trabecular thickness.
RESULTS: Cartilage volume and thickness were less in patients with OA compared to normal controls (P<0.1). Articular cartilage thinning is associated with bone structure loss in the opposite femoral condyle (P<0.05). In varus OA, there were extensive correlations between medial tibia and medial femoral cartilage degeneration, and loss of bone structure in the lateral tibia and lateral condyle. Additional correlations existed between the compartmental differences (lateral minus medial) of cartilage thickness and bone structure.
CONCLUSION: Degradation of articular cartilage within a compartment correlates with a loss of bone structure in the opposite compartment. The correlation between the (L-M) differences corroborates this relationship. Malalignment of the knee due to cartilage degeneration is associated with bone formation in the diseased condyle and bone resorption in the opposite compartment.