Plantar fasciitis is a clinical diagnosis and is often combined with some form of imaging to validate the diagnosis. The clinical utility of lateral X-rays ties in the fact that they are relatively inexpensive and may contribute to ruling out other osseous causes of pain. In this study 106 (27 plantar fasciitis (PF) and 79 controls) plain non-weight bearing lateral X-rays were examined by a blind examiner to document the key features of the lateral X-ray between images of individuals with and without plantar fasciitis. As expected calcaneal spurs were observed in both groups (85% PF and 46% controls). However, plantar fascia thickness and fat pad abnormalities resulted in the best group differentiation (p < 0.0001) with sensitivity of 85% and specificity of 95% for plantar fasciitis. It was concluded that the key radiological features that differentiate the groups were not spurs but rather changes in the soft tissues. If it is deemed necessary to confirm the diagnosis of typical plantar fasciitis with imaging, a lateral non-weight bearing X-ray should be the first choice investigation especially if these key features are noted. (c) 2006 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.