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Background: Osteochondral lesions of the talus (OLT) often require advanced imaging if they prove to be refractory to preliminary microfracture. Orthopedic surgeons may misinterpret the size and morphology of the OLT when evaluating through conventional methods. The purpose of this study was to evaluate MRI as a modality for calculating true-volumes and compare its utility to that of CT true-volume and conventional methods of measuring lesion size. Methods: With IRB approval, an institutional radiology database was queried for patients with cystic OLT that had undergone and failed microfracture and had compatible CT and MR scans between 2011 and 2016. Five lesions, previously analyzed and described in the literature using CT true-volume, were selected. 10 orthopedic surgeons independently estimated the volume of these 5 OLT via standard MRI. Next, 3D reconstructions were created and morphometric true-volume (MTV) analysis measurements of each OLT were generated. The percent change in volumes from CT and MR was compared based upon MTVs determined from 3D reconstructive analysis. Results: The volume calculated using conventional methods in CT and MR scans grossly overestimated the size by of the OLT by 285-864% and 56-374% respectively when compared to 3D true-volume analysis of those CT and MR scans. Conclusions: This study demonstrates that true-volume is more accurate for calculating lesion size than conventional methods. Additionally, when comparing MRI and CT, thin slice CT true-volume is superior to MRI true-volume. True-volume calculation improves accuracy with CT and MRI and should be recommended for use in revision OLT cases. Levels of Evidence: Level III: Case control study