The osseous manifestations of osteochondrosis dissecans are well demonstrated by conventional and computerised tomography. Beyond that, magnetic resonance imaging (MRI) is effective in evaluating the vitality and loosening of an osseous dissecate. Subchondral cavities and cartilaginous defects are detected with high accuracy. Further, MRI seems to be a useful method in childhood to differentiate a variant irregularity of the osseous articular surface from definite osteochondrosis dissecans.