Stress fracture

Last revised by Keshaw Kumar on 26 Jan 2024

Stress fractures refer to fractures occurring in the bone due to a mismatch of bone strength and chronic mechanical stress placed upon the bone.

A pathological fracture, although a type of insufficiency fracture, is a term in general reserved for fractures occurring at the site of a focal bony abnormality. Some authors use the term stress fracture synonymously with fatigue fracture, and thus some caution with the term is suggested.

Fatigue fractures are common in athletes, especially runners and military recruits. Insufficiency fractures occur more in women and older people 7,8.

The following conditions increase the risk of a stress injury 8:

  • female sex

  • low bone density

  • nutritional disorders or deficiencies

  • 'female athlete triad'

  • long-distance running

  • inappropriately short recovery time

  • training changes

  • inadequate shoes

Stress fractures normally present with worsening pain with a history of minimal or no trauma. In the lower (weight-bearing) limb, there is often a history of a recent increase of physical activity or significant alteration in the type or duration of normal athletic activity.

A stress fracture is the final stage of a stress injury and occurs if the bone fails to withstand a repetitive, cumulative loading force and is no longer capable to mitigate that loading stress with its own healing capabilities and breaks 7.

Stress fractures are far more common in the lower limb (~95%) than in the upper limb 5. High-risk sites of stress fractures are locations at greatest risk of a progression to complete fracture, displacement or non-union as these sites are under tensile stresses and have poor vascularity 9-11:

  • pars interarticularis of the lumbar spine

  • thigh and leg: femoral neck, patella, anterior tibial cortex

  • ankle and foot: medial malleolus, talus, navicular, 2nd to 4th metatarsal necks, 2nd metatarsal base, 5th metatarsal, hallux sesamoid

Low-risk sites of a stress fracture are at low risk of complications and are under compressive stresses 10,11:

  • ribs

  • proximal humerus/humeral shaft

  • pelvis: sacrum, pubic rami

  • lower limb: calcaneus, posterior medial tibial shaft, fibula, lateral malleolus, 2nd to 4th metatarsal shafts

Plain radiographs have poor sensitivity (15-35%) in early-stage injuries, which increases in late-stage injuries (30-70%), due to possible callus formation. 

MRI is the most sensitive modality for diagnosis of a stress fracture and is an important tool to distinguish high and low-risk fractures to help clinicians with management plans and a sensitivity reported to reach close to 100% 5,6.

Plain radiographs have poor sensitivity in detecting stress fractures, as positive findings may take months to appear. During the first few weeks after the onset of symptoms, x-rays of the affected area may look normal.

Positive findings can include:

  • grey cortex sign: subtle loss of cortical density in early-stage stress injury

  • increasing sclerosis or cortical thickening along the fracture site

  • periosteal reaction/elevation

    • may take up to 2 weeks to be detectable

  • fracture line

Bone scans can show evidence of stress fracture within a few days upon the onset of symptoms. As a modality, it is considered less sensitive than MRI 5.

Stress fractures on bone scintigraphy appear as foci of increased radioisotope activity ('hot spot') due to increased bone turnover at the site of new bone formation. However, as with all bone scintigraphy, this is non-specific; the increased uptake can also be due to osteomyelitis, bone tumors or avascular necrosis.

The findings are similar to plain radiography, including sclerosis, new bone formation, periosteal reaction, and fracture lines in long bones.

CT may be useful in differentiating stress fractures from a bone tumor or osteomyelitis if the plain radiographs are negative and bone scans are positive.

MRI is the most sensitive modality for detecting stress fracture, and may also be useful for differentiating ligamentous/cartilaginous injury from a bony injury.

Typical MRI appearance of stress fracture includes:

  • periosteal or adjacent soft tissue edema

  • band-like bone marrow edema

  • T1 hypointense fracture line evident in high-grade injury

The use of MRI grading system for bone stress injuries is helpful for predicting recovery time (important especially for athletes).

Treatment is determined by the site of the stress fracture and suitability for rehabilitation.

Fractures at low-risk sites are managed conservatively with analgesia, ice, reduced weight-bearing and modification of activities until pain resolves.

At high-risk sites or in patients where long-term rehabilitation is detrimental to their livelihood (i.e. athletes or laborers), orthopedic consultation is required.

Risk factors such as diet, vitamin D and calcium should be addressed to prevent recurrence. Other factors such as a gradual return to training and biomechanical evaluation of gait may be required. Bone density evaluation can be considered in patients with recurrent stress fractures, family history of osteoporosis or stress fractures unexplained by exercise activity.

  • osteosarcoma and bone tumors can also present with periosteal reaction

  • osteomyelitis has marrow edema and soft tissue swelling

  • soft tissue bruise: has edema at the injury site, but little marrow abnormality

  • in addition to the risk stratification by location, any displacement or proximal femur fractures with a fracture line >50% the width of the femoral neck should also be considered high-risk 6

  • calcaneal stress fractures are typically parallel to posterior cortex

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Cases and figures

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  • Case 5
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  • Case 6
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  • Case 7
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  • Case 8: involving left femoral neck in a child
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  • Case 9: involving distal tibia on MRI
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  • Case 10
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  • Case 11
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  • Case 12
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  • Case 13
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  • Case 14
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  • Case 15
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  • Case 16: bone scan static images
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  • Case 17: of the second metatarsal
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  • Case 18: femoral neck stress fracture
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  • Case 19
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  • Case 20: pubic ramus stress fracture
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  • Case 21: second metatarsal
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  • Case 22: second metatarsal
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  • Case 23: third metatarsal shaft
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  • Case 24: metatarsal stress fracture
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  • Case 25: ultrasound
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  • Case 26: medial tibial condyle
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  • Case 27: distal tibia and calcaneum
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  • Case 28: shoulder
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  • Case 29: humeral neck stress fracture with concomitant distal clavicular osteolysis
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  • Case 30 stress fracture of proximal tibia
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