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It had been suggested that the term stress fracture be restricted to cases of osseous structural failure detected radiographically by a fracture line and that the term stress reaction be used to describe the series of changes in bone pathophysiology associated with repetitive loading [19]. As identification of a discrete fracture line is temporally and modality dependent, an accurate description is fundamental to interpretation.

Initial findings in cortical bone can include a subtle radiolucent zone or faint intracortical radiolucent striations followed by periosteal and endosteal new bone and in some cases the appearance of a delicate fracture line [20]. Further periosteal callus, endosteal thickening and increased opacity (sclerosis) and a frank fracture line may be identifiable at a later time point [21–24]. The reactive bone is generally confined to a small area and usually involves only one cortical surface. Ultimately, the area of periosteal reaction thickens and the fracture line, if seen previously, disappears [21]. Following trabecular microfracture, osteoblasts lay down new bone along the injured trabeculae. Depending upon the timeline, this may produce subtle blurring of the trabeculae with faint increased radiopacity and later thickened trabeculae producing more evident sclerosis secondary to peri‐trabecular callus [20, 25]. Trabecular bone is reported to have a metabolic turnover eight times faster than cortical bone [26], leading to the possibility that subtle changes may be identified in this location first.

In man, the limitations of conventional radiographs for detection of stress injuries are well documented [2227–29]. The multifaceted variables in the continuum of the stress response account for the variation in radiographic appearance [30]. Given the microscopic remodelling that occurs in the early stages of a stress injury, the overall sensitivity of radiographs can be low and findings may be reserved until the healing phase, 12–21 days [14, 20,31–34] and in some instances four to six weeks [35] after a stress fracture, has occurred (see Figure 5.10a and c). Advances in radiography since the digital era have made subtle changes easier to recognize, but sometimes fractures never become radiographically apparent [34,36–39].

If a fracture is identified, this provides a risk bracket for the patient which assists with management strategies and whether the nature of the changes supports radiographic monitoring. If the radiographs are negative, depending upon the area, it may be advisable to repeat radiographic examination in 7–14 days and/or consider an alternative imaging modality.