Bone stress injury: Common imaging-based grading scales

	Fredericson	Kaeding-Miller	Nattiv
Grade 1	Periosteal edema only	Imaging signs of BSI No pain	Mild edema in marrow or periosteum
Grade 2	Bone marrow edema only on T2-weighted MRI images	Imaging signs of BSI Pain in affected area	Moderate edema in marrow or periosteum
Grade 3	Bone marrow edema on T1- and T2-weighted MRI images	Nondisplaced fracture line	Severe edema in marrow or periosteum Without fracture line
Grade 4	Intracortical MRI signal abnormalities including fracture line	Displaced fracture	Severe edema in marrow or periosteum Visible fracture line
Grade 5		Nonunion

BSI: bone stress injury; MRI: magnetic resonance imaging.

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