This book focuses on musculoskeletal diseases encountered in the shoulder, upper extremity, pelvis, and lower extremity that are problematic because they are less common, relatively recently described, or can mimic more common pathology leading to a misdiagnosis. This work demonstrates succinct imaging findings that differentiate these less common findings or normal variant mimickers from the more common similar-appearing diseases so as to prevent misdiagnosis. This text will function as a useful resource to both residents and general practicing radiologists when they encounter problematic imaging findings that resemble a common disease, and yet the imaging findings just don’t quite seem like the common disease. The collection of diseases in this book has been drawn from the literature (text) as well as the substantial teaching and clinical experience of the authors (images). The final chapter of the text functions as a succinct review of musculoskeletal tumors and tumor-like lesions encountered in a general radiology practice.