Ultrasonographic evaluation of joint damage in knee osteoarthritis: feature-specific comparisons with conventional radiography

A total of 166 knees of 84 patients (59 women and 25 men) with primary knee OA were included in this study. The femoral hyaline cartilage of the medial para-patellar aspect and the osteophytes of both the medial and lateral femoral condyle were assessed. The cartilage and osteophytes were both quantitatively and qualitatively assessed. The US assessment was feature-specifically compared with conventional radiography. There was a strong correlation between the radiographic medial tibiofemoral narrowing grade and the US medial cartilage grade (rs = 0.7144, 95% CI: 0.6218, 0.7873, P < 0.0001). In the detailed analysis, US could assess cartilage damage more correctly by using the direct visualization technique. A strong correlation was also found between the radiographic and the US medial femoral osteophyte grade (rs = 0.7515, 95% CI: 0.6659, 0.8176, P < 0.0001) and between the radiographic and the US lateral femoral osteophyte grade (rs = 0.6947, 95% CI: 0.5941, 0.7739, P < 0.0001). US detected osteophytes in 46 sites at which conventional radiography did not detect any osteophytes. The present feature-specific comparison study provides evidence supporting the concurrent validity of US in the assessment of knee joint damage due to OA through its agreement with conventional radiography. Moreover, US was found to be a sensitive imaging technique for revealing cartilage damage and even minimal osteophytes, especially in the early radiographic stages of knee OA.