The reasoning
| Fatigue fracture | Insufficiency fracture | |
|---|---|---|
| Bone | normal | weakened (osteoporosis, osteomalacia, RA, steroids, radiation, Paget's, fibrous dysplasia, renal osteodystrophy, bisphosphonates: atypical femoral) |
| Stress | abnormal, repetitive | normal physiological |
| Patients | military recruits, runners, dancers, athletes | elderly women, steroid users, post‑radiotherapy (sacrum, pelvis) |
| Sites | metatarsals (2nd/3rd: march fracture), tibia (shaft; anterior cortex "dreaded black line" in jumpers: high risk), calcaneus, navicular, femoral neck (tension side superolateral: high risk), pars interarticularis (spondylolysis), fibula, pubic rami | sacrum (H‑shaped "Honda" sign on bone scan), pubic rami, supra‑acetabular, femoral neck, distal tibia, calcaneus |