Summary A tibial shaft stress fracture is an overuse injury where normal or abnormal bone is subjected to repetitive stress, resulting in microfractures. Diagnosis can often be made on radiographs alone but MRI studies should be obtained in patients with normal radiographs with a high degree of suspicion for stress fracture. Treatment is activity restriction with protected weight-bearing in most cases. Surgical intramedullary nailing is recommended in the presence of an anterior tibia tension-sided stress fracture ("dreaded black line"). Epidemiology Demographics commonly seen in runners and military recruits seen after change in training routine Etiology Mechanism linear microfractures in trabecular bone from repetitive loading Pathophysiology callus formation woven bone endochondral bone formation Presentation History change in exercise routine Symptoms onset of symptoms often insidious symptoms initially worse with running, then may develop symptoms with daily activities Physical exam pain directly over fracture Imaging Radiographs recommended views AP and lateral findings lateral xray may show "dreaded black line" anteriorly indicating tension fracture from posterior muscle force endosteal thickening periosteal reaction with cortical thickening Technetium Tc 99m bone scan findings focal uptake in cortical and/or trabecular region MRI replacing bone scan for diagnosis and is most sensitive findings marrow edema earliest findings on T2-weighted images periosteal high signal T1-weighted images show linear zone of low signal Treatment Nonoperative activity restriction with protected weightbearing indications most cases technique avoids NSAIDs (slows bone healing) consider bone stimulator Operative intramedullary tibial nailing indications if "dreaded black line" is present, especially if it violates the anterior cortex fractures of anterior cortex of tibia have highest likelihood of delayed healing or non-union