Subchondral bone changes are thought to be an important aetiological element in the pathogenesis of osteoarthritis (OA). To confirm this hypothesis in the meniscectomized (MNX) guinea pig model, bone densitometry was performed in the subchondral bone of the distal femur.
MNX and sham-operated (SH) guinea pigs were studied 1 and 3 months after partial meniscectomy at the medial side of the left knee. Bone mineral density was measured at the lateral (BMD-L) and medial (BMD-M) sides of the distal femur using dual-energy X-ray absorptiometry (DXA). BMD-M was then compared to the bone volume evaluated by histomorphometry at the medial epiphyseal part of the proximal tibia (BV-M).
One month after operation, in MNX animals left femur BMD-M was significantly lower than in the contralateral femur (-9%, P< 0.01) and than in the left femur of SH (-11%, P< 0.01). By contrast, 3 months after meniscectomy BMD-M was higher in the femur than in the contralateral femur (+4%, P< 0.05); BV-M tended to be higher on the left than on the right side (+4%, P< 0.06), and was significantly correlated with BMD-M at the 2 grouped time points: r=0.74 (P< 0.001).
These data emphasize the usefulness of DXA as a simple tool to assess subchondral bone changes at the OA-affected side of the femur and reveal typical variations of bone metabolism in the initiation of OA pathology in the MNX guinea pig: early bone loss at the subchondral level followed by increased bone density.