Indications of inflammation visualized by ultrasound in osteoarthritis of the knee

PURPOSE: Ultrasound examination of a group of patients with osteoarthritis (OA) of the knee for signs of inflammation. MATERIAL AND METHODS: 71 knees in 71 patients with osteoarthritis of the knee were examined with high-resolution gray-scale ultrasound combined with color and spectral Doppler. The medial, lateral, and antero-superior compartments were examined. Hyperemia was identified as presence of color Doppler signals in the synovial membrane. Low resistance flow was defined as a resistive index < 0.80 on spectral Doppler. RESULTS: Synovial thickening was found in all knees; fluid in 61 patients; and hyperemia (color Doppler activity) in 51 patients. Of these, 44 had arterial flow on spectral Doppler - 36 with a low resistance flow. When present, fluid and color Doppler activity was found in all three compartments, but with uneven distribution. CONCLUSION: The finding in the majority of cases of both effusions on B-mode US and Doppler activity confirms that there is a varying degree of inflammation in knee OA as diagnosed by the ACR criteria.