Causes / typical injury mechanism: Stress fractures of the lower limb, including calcaneal stress fractures, are caused by repeated physical stress below the threshold for acute fracture. Insufficient rest periods between activities prevent bone healing and new bone formation. Calcaneal stress fractures most often occur in the posterior and superior calcaneus.

Calcaneal stress fractures, along with stress fractures of the lateral malleolus, are considered low-risk stress fractures with minimal risk of progression and complication.

Classic history and presentation: These fractures classically present as exercise-induced heel pain following long periods of repeated stress or long-distance running. They are also noted in older, less active patients with chronic medical problems and/or poor bone density.

Prevalence: Few studies with large sample sizes have attempted to characterize the true prevalence in the general population. However, they represent a common injury in both athletes and military members. They were found to comprise 20% of foot stress fractures in male military recruits and 39% in females.

Risk factors: Female sex and poor bone density have been associated with greater rates of stress fractures; however, little data exists on a specific association with calcaneal stress fractures. Calcaneal stress fractures are seen most often in military recruits that frequently experience sudden changes in the level of physical stress.

Grade / classification system: Stress fractures can be classified by MRI imaging characteristics –

• I: Endosteal marrow edema
• II: Periosteal edema and endosteal marrow edema
• III: Muscle edema, periosteal edema, and endosteal marrow edema
• IV: Visible fracture line(s)