Effects of hyaluronic acid on meniscal injury in rabbits.

Using a model of meniscal injury in rabbit, the effects of hyaluronic acid (HA) injection into the joint on the rate of filling area and the cell shape in the defects were studied. After a cylindrical defect was made in the anterior horn of the lateral meniscus, HA was injected into the joint once a week. At 1 and 6 weeks after the beginning of the weekly injections, the meniscus was compared with a control, which was injected with phosphate buffer instead of HA. The healing in the defect progressed with time. HA administration caused a significant increase in the rate of filling area in the defect. The cell population in the repair tissue changed from fibroblast-like cells to chondrocyte-like cells with the progress of repair. At 6 weeks, the ratio of chondrocyte-like cells to all cells in the repair tissue of the HA-treated meniscus was higher than that of control. These data indicate that HA increases the healing rate of meniscal injury.