Representative plain radiographs of the hind paws obtained at the end of the experiment. The (a) control, (b) methotrexate (MTX), (c) zoledronic acid (ZA), and (d) ZA + MTX groups are shown. Severe loss of subchondral bone was seen in the control group, with multiple areas of erosion, whereas lower levels of destruction were observed in MTX-treated rats. ZA completely prevented bone destruction. (e) Soft-tissue swelling and erosion radiographic score for the ankle and tarsus joints. ZA alone or in combination with MTX significantly decreased the erosion score, but had a pro-inflammatory effect, increasing soft-tissue swelling. MTX also decreased the number of areas of erosion and decreased the soft-tissue swelling. *P < 0.05 versus computed tomography (CT) group.