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Background: The diagnostic value of an oblique radiograph, in addition to a lateral radiograph, for detecting osteophytes in the anterior ankle impingement syndrome was evaluated in a prospective study. The hypothesis was that the application of a lateral radiograph is insufficient to detect osteophytes that are located in the anteromedial aspect of the ankle joint. Oblique anteromedial impingement (AMI) radiographs were hypothesized to be a relevant adjunct, because of their utility to detect these anteromedially located osteophytes. Methods: Presence or absence of tibial and talar osteophytes on both radiographs was compared with the combined findings of CT, MRI scan, and arthroscopic surgery. Estimates of test characteristics were obtained for 60 consecutive patients with an anterior ankle impingement syndrome. Results: It was shown that the sensitivity of lateral radiographs for detecting anterior tibial and talar osteophytes was 40% and 32%, respectively (specificity, 70% and 82%). When the lateral radiograph was combined with an oblique AMI radiograph, these figures increased to 85% and 73%, respectively (specificity decreased to 45% and 68%). This increase was due to the high sensitivity of the oblique AMI radiographs for detecting anteromedial osteophytes (93% for tibial and 67% for talar osteophytes). Conclusion: A lateral radiograph is insufficient to detect all anteriorly located osteophytes. An oblique AMI radiograph is a useful adjunct to routine radiographs and is recommended to detect anteromedial tibial and talar osteophytes.