PURPOSE: To investigate the usefulness of sonography for the evaluation of osteoarthritic articular cartilage. MATERIALS AND METHODS:Ten asymptomatic volunteers and 20 patients with osteoarthritis of the knee under-went sonographic evaluation. For this, the knee was maintained of full flexion in order to expose the deep portion of femoral condylar cartilage. Both transverse and longitudinal scans were obtained in standardized planes. Sonographic images of the articular cartilages were analyzed in terms of surface sharpness, echogenicity and thickness, along with associated bone changes. RESULTS: Normal cartilages showed a clearly-defined surface, omogeneously low echogenicity and regular thickness. Among 20 patients, the findings for medial and lateral condyles, respectively, were as follows: poorly defined cartilage surface, 16(80%) and ten(50%); increased echogenicity of cartilage, 17(85%) and 16(80%); cartilage thinning, 16(80%) and 14(70%) (two medial condyles demonstrated obvious cartilage thickening); the presence of thick subchondral hyperechoic bands, five (25%) and four (20%); the presence of osteophytes, 13 (65%) and 12(60%). CONCLUSION: Sonography is a convenient and accurate modality for the evaluation of femoral articular cartilage. In particular, it can be useful for detecting early degenerative cartilaginous change and for studying such change during clinical follow-up.