Interrelationship between trabecular bone and articular cartilage of the knee joint in early OA

Radu I. Bolbos, Jin Zuo, Ben Hyun, Suchandrima Banerjee, Thomas M. Link, C. Benjamin Ma, Xiaojuan Li, Sharmila Majumdar

Osteoarthritis (OA) is a degenerative joint disease that typically affects the weight-bearing knee joints. It was suggested that pathological alterations at the early stage of OA primarily affect the articular cartilage and the underlying bone. The articular cartilage’s early changes consist of an increase in water content, a loss of proteoglycans (PGs) and the disruption of collagen fibers, while for trabecular bone, the volumetric mineral density decreases due to incomplete mineralization of trabecular structure. High resolution quantitative magnetic resonance imaging (qMRI) provides a way to directly assess the integrity — thickness and

volume — and composition — T1ρ, T2 — of the articular cartilage, as well as to depict the trabecular microstructure: bone fraction (BV/TV), trabecular number (Tb.N), thickness (Tb.Th), and spacing (Tb.Sp). Previous studies have demonstrated increased T1ρ and T2 values with the degree of OA. Significant variations in trabecular bone structure at different stages
08/21/2008 of OA were also reported. The aim of this study was to evaluate trabecular bone structure in relationship with cartilage parameters in distal femur and proximal tibia of the human knee at 3 Tesla using high resolution MRI with parallel imaging.

Negative correlations were found between trabecular bone and cartilage matrix parameters from the same compartment, indicating that deterioration of trabecular bone structure is directly proportional to the increasing values of T1ρ and T2. Positive correlations were found between trabecular structure and cartilage thickness and volume, suggesting that loss of mineralized trabecular bone is associated with cartilage morphological degradation.

Significant correlations between contro-lateral sides of knee joint were also found, indicating that loss of mineralized trabecular bone on one side of knee joint is related with cartilage loss on the opposite side. This aspect states that the association between cartilage changes in one compartment and relative osteopenia in the opposite compartment suggest that slight varus or valgus angular malalignment as result of cartilage degeneration consequently unloads the biomechanical forces in the nondegenerated compartment of the knee.