Arthroscopy in spontaneous osteonecrosis of the knee.

Eight knees with spontaneous osteonecrosis were investigated through arthroscopy, and in seven the intra-articular findings were rechecked at arthrotomy performed one to two weeks later. Anbormalities in the articular cartilage were observed in detail under arthroscopy that could not be seen in roentgenograms. In the early stage of osteonecrosis, flattening and fissures in the articular surfaces, with and without formation of a cartilage flap, were useful findings in choosing intra-articular surgical procedures. In the late stage, free bodies such as cartilage plates in the joint and regeneration with fibro-cartilaginous tissue over the necrotic lesion were also important in selecting surgical treatment. In addition to roentgenographic classification of developmental stages in osteonecrosis, arthroscopy is necessary in differentiating osteoarthroses, in observing the articular surface of the femoral condyles, and in determining the stage of disease when roentgenography provided insufficient information to justify intra-articular procedures such as drilling and bone grafting.