The classification of stress fractures into high risk or low risk has been suggested by multiple authors [4,5,26]. This distinction allows the medical staff to quickly determine whether they can be aggressive or conservative with their decision to return an athlete to participation. Low-risk stress fractures include the femoral shaft, medial tibia, ribs, ulna shaft, and first through fourth metatarsals—all of which have a favorable natural history. These sites tend to be on the compres-sive side of the bone and respond well to activity modification. Low-risk stress fractures are less likely to recur, become a nonunion, or have a significant complication should it progress to complete fracture. Management of these injuries is discussed later and is guided primarily by the individuals' symptoms.

In comparison to low-risk stress fractures, high-risk stress fractures do not have an overall favorable natural history. With delay in diagnosis or with less aggressive treatment, high-risk stress fractures tend to progress to nonunion or complete fracture, require operative management, or recur in the same location [27]. High-risk stress fracture locations include the femoral neck, the patella, the anterior tibial diaphysis, the medial malleolus, the talus, the tarsal navicular, the proximal fifth metatarsal, and the first metatarsal phalengeal seasmoids. It is clear that location determines whether a stress fracture is low risk or high risk.

In addition to knowing the classification of a stress fracture as high versus low risk as determined by its anatomic site, the extent of the fatigue failure or the grade of the stress fracture is also needed to completely describe the injury. As mentioned earlier, stress injuries to bone create a continuum, from mild micro-failure to cortical disruption to complete fracture. There have been two previously published grading scales for the stress reaction/fracture continuum. The scale published by Arendt and Griffiths [21] has been used for the femur, tibia, fibula, navicular, calcaneus, and forefoot, whereas the scale published by Fredericson and colleagues [28] was developed using data for the tibia alone. Both scales consider grade 4 to be a complete stress fracture and grades 1 to 3 to be increasing levels of periosteal changes and marrow edema. One large study by Arendt and Griffiths [21] demonstrated that grade 3 and 4 injuries took longer to heal than grade 1 and 2 injuries. This study demonstrated that the grade of injury has prognostic implications regarding the time of healing. The management of bony stress injuries should be based on the location and grade of the injury. These two details give the amount of microdamage that has accumulated and whether it is a high- or low-risk injury. The following discussion focuses on treatment and return-to-play strategies for stress fractures depending on their anatomic location and associated classification as high or low risk.

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