The bursa suprapatellaris, infrapatellaris, the patella tendon, condylar cartilage, menisci and fossa poplitea were examined sonographically in 56 healthy persons in defined sections. References for normal findings are given. The examination of 22 patients with rheumatoid arthritis revealed joint effusions, Baker cysts, synovial hypertrophy, intraarticular septae and changes in the echogenicity of the synovial fluid.