A calcaneal stress fracture is a small crack or series of microscopic cracks that develops within the heel bone after repeated mechanical loading. Unlike an acute fracture caused by a major injury, a stress fracture develops gradually when the bone is exposed to repetitive forces that exceed its ability to repair itself.
The calcaneus is the largest bone in the foot and absorbs enormous forces during walking, running and jumping. Under normal circumstances, bone continually remodels itself by repairing microscopic damage that occurs with everyday activity. However, when loading increases too quickly or recovery is inadequate, these tiny areas of damage accumulate faster than they can heal. Initially this produces a bone stress reaction, often seen on MRI as bone marrow oedema. If loading continues, a true stress fracture may develop.
One of the reasons calcaneal stress fractures are commonly missed is that the symptoms closely resemble other causes of heel pain, particularly plantar fasciosis. Patients often report pain beneath the heel that gradually worsens over several weeks. Because plantar fasciosis is much more common, many patients are initially treated with stretching exercises, orthotics or shockwave therapy before the correct diagnosis is considered.
There are, however, several important differences. Patients with plantar fasciosis typically experience marked pain with their first few steps after resting, which often improves as they warm up. In contrast, patients with a calcaneal stress fracture frequently find that the pain worsens the longer they walk or run. As the injury progresses, everyday activities such as prolonged standing may also become increasingly uncomfortable.
Stress fractures are most common in runners, military recruits and athletes who rapidly increase their training intensity. However, they are not limited to athletes. People who suddenly begin a walking programme, start a physically demanding occupation or significantly increase their daily activity can also develop stress fractures if the bone is unable to adapt quickly enough.
Certain medical conditions may increase the risk. Osteoporosis, vitamin D deficiency, low energy availability, eating disorders, long-term corticosteroid use and other conditions affecting bone health can reduce the bone's ability to tolerate repetitive loading. Identifying these risk factors is important because successful treatment depends on addressing both the fracture and the underlying cause.
Diagnosis begins with a detailed clinical assessment. Patients often have tenderness when the heel bone is compressed from the sides, and hopping on the affected foot may reproduce symptoms. However, these findings are not specific, and imaging is usually required to confirm the diagnosis.
Plain X-rays are frequently normal during the early stages because microscopic fractures are not immediately visible. MRI is the most sensitive investigation, allowing detection of both bone marrow oedema and stress fractures before changes appear on X-ray. In some situations, CT scanning may also be helpful, particularly if the extent of the fracture requires further evaluation.
Treatment differs significantly from plantar fasciosis. A stress fracture requires protection from continued loading to allow the bone to heal. Continuing to run or participate in high-impact activities despite worsening symptoms increases the risk that the fracture will enlarge or healing will be delayed. Most patients recover successfully with activity modification, appropriate immobilisation where necessary and a gradual, structured return to weight-bearing.
The key message is that not every painful heel is caused by the plantar fascia. When heel pain progressively worsens with activity, fails to improve with appropriate treatment or develops after a sudden increase in exercise, a calcaneal stress fracture should be considered. Early diagnosis allows appropriate treatment to begin before a relatively small injury becomes a more significant fracture.