Experimental osteoarthritis was induced in six adult dogs by intraarticular injection of sodium monoiodoacetate in left knee joints. The contralateral knees served as control. The changes occurring in joints were followed out by radiography and ultrasound imaging in the beginning (day 0), and on post injection days 30, 60, and 105. Two assessment systems were used to generate individual scores for each time interval. The results evidenced dynamic and consistently increased scores for left joints in both diagnostic imaging techniques used with statistically significant differences between left and right joints. Radiological and ultrasound scores were closely correlated (r=0.55, P<0.001) suggesting that the combined use of both imaging techniques was more advantageous for diagnostics of osteoarthritis.