The purpose of this study was to describe the spectrum of radiologic and pathologic manifestations of calcific tendinitis involving bone. We retrospectively reviewed 50 cases of calcific tendinitis involving underlying bone. Clinical data reviewed included patient age and sex and lesion location. Images reviewed included radiographs (n = 44), CT scans (n = 13), MRIs (n = 16), and bone scintigrams (n = 13). Radiologic examinations were evaluated for the presence of cortical erosion, periosteal reaction, and marrow extension. Pathology confirmation was available in 37 cases. The average age of patients was 50 years (range, 16-82 years), with 29 female patients (58%). Calcific tendinitis with associated bone involvement was seen most commonly in the femur (40%) and the humerus (40%). Concretions were most commonly solid-appearing (50%). Cortical erosion was the most common manifestation of osseous involvement (78% of cases). Marrow involvement was shown in 18 (36%) of 50 cases. Marrow extension was most commonly seen in the lesser and greater tuberosities of the humerus, which accounted for 61% (11/18) of cases. Focal increased radionuclide uptake was seen in 13 (100%) of 13 cases. Calcific tendinitis presenting with osseous destruction, marrow changes, and soft-tissue calcifications may be confused with neoplasm both radiologically and pathologically. Recognition of the atypical presentation of this common disease may prevent unnecessary biopsy.