Twelve athletes presenting acute knee injury with normal radiological findings underwent both three-phase radionuclide bone imaging (TPBI) and magnetic resonance imaging (MRI). The association of these highly sensitive diagnostic procedures detected occult fractures in all patients. The areas of signal intensity alterations on MRI corresponded to those of increased radionuclide uptake in blood pool images. However, the same areas seemed to be more extended on delayed TPB images. TPBI yielded early diagnostic information about lesion sites and functional activities, while MRI provided better anatomical definition and specific information about associated soft tissue lesions and served to establish the correct therapeutic approach and follow-up.