[The staging of osteochondritis dissecans in the knee and ankle joints with MR tomography. A comparison with conventional radiology and arthroscopy].

PURPOSE: A prospective study was performed on 50 patients suffering from osteochondritis dissecans of the knee and ankle to define criteria for stability and fixation of osteochondral lesions.

METHODS: Morphological parameters in MRI (size, fragmentation, cartilage, interface) and conventional radiology (separation, fragmentation) were registered and compared with arthroscopic staging. MRI staging based on different types of interfaces was demonstrated on T1- and T2-weighted images.

RESULTS: MRI could correctly predict a Grade 1 lesion in 50%, a Grade 2 lesion in 90%, a Grade 3 lesion in 0%, and a Grade 4 lesion in 79%. Stable lesions were differentiated from unstable lesions in 90%. Radiographic findings corresponded with arthroscopic staging in only 56% of the cases because fibrotic connection may guarantee stability in cases of bony separation.

CONCLUSION: MRI should be performed before therapy to select those patients who do not need surgical therapy or arthroscopy.