With the Auckland and Queenstown Marathons approaching, thousands of runners are increasing their weekly mileage and tackling their longest training runs. For this reason, it's also the time of year when we see an increase in bone stress injuries at Axis.

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For physiotherapists and other primary care clinicians managing runners, these injuries can present a challenge. The runner has often invested significant time and energy in training, has a programme they are keen to stick to, and may present with symptoms that initially appear relatively minor. To complicate matters, X-rays are often normal early in the course of a bone stress injury. In fact, initial X-rays may be negative in more than 60% of cases and some bone stress injuries never develop diagnostic X-ray changes. This can make what is generally a straightforward diagnosis surprisingly easy to miss.

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Recognising a Bone Stress Injury

The typical presentation of an insidious onset of increasingly localised pain, often following an increase or change in running load. Initially, symptoms may only appear towards the end of a run but as the injury progresses, pain tends to start earlier, become more intense and persist for longer afterwards. More advanced injuries may become painful with walking or normal daily activities. Localisation is an important clue. A runner who can point with one finger to a focal area of bony tenderness should raise suspicion, particularly following a recent change in training load.

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Not every bone stress injury presents this neatly. Navicular stress injuries are a good example. Symptoms may be surprisingly vague, with poorly localised dorsal or midfoot pain. This contributes to significant delays in diagnosis. Studies have reported delays of several months, with one systematic review finding an average duration of symptoms approaching 10 months before diagnosis. Similarly, femoral neck stress injuries can present as relatively non-specific hip or groin pain and may have a relatively normal hip examination. These are important injuries to identify because some bone stress injury locations have a significantly less favourable natural history if missed.

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Imaging is important. X-rays are almost always the first investigation but have limited sensitivity, particularly early in the injury. MRI can confirm the diagnosis, identify the site and provide information about its severity.

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Severity and Location Matter

For the runner, the question is invariably can I still run, and how long do I need to rest for? The answer is more nuanced than many people expect.

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Bone stress injury is best thought of a continuum rather than a binary diagnosis. Repetitive loading initially produces a normal bone-remodelling response. If loading continues to exceed the bone's capacity to recover, this can progress through increasing bone oedema (stress reaction) and ultimately to the development of a fracture line (stress fracture). MRI can help us determine where an athlete sits on this spectrum, and this has practical implications. Research using MRI grading has demonstrated progressively longer return to sport times with increasing injury severity.

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Across studies, low-grade injuries have returned to sport considerably sooner than injuries where the fracture line is present. We see the same clinically. Some runners present when the bone has only recently tipped over into becoming symptomatic. They may have a short history, relatively mild symptoms and low-grade changes on imaging. In these patients the period of unloading required may be relatively short.

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At the other end of the spectrum is the runner who has continued training for weeks or months despite worsening symptoms and has more advanced imaging changes. Their rehabilitation will look quite different. The site of injury is equally important. Many bone stress injuries occur at relatively low-risk sites and heal predictably with appropriate load modifications. Others, including injuries involving the navicular, femoral neck, anterior tibial cortex and base of the fifth metatarsal, require greater caution because of their potential for delayed healing, non-union or progression.

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Planning the Right Return to Running

Combining the history, examination and imaging allows us to determine how much unloading is actually required. This is particularly valuable when there is a race on the horizon. An early, low-grade injury at a favourable site is very different from an established injury at a high-risk site.

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A diagnosis of bone stress injury therefore doesn't necessarily end someone's marathon preparation, but continuing to run without knowing what you are dealing with can turn a manageable injury into a much bigger problem. At Axis, our role is to establish the diagnosis and work alongside the treating clinician and runner to develop an individualised rehabilitation plan. This includes arranging appropriate imaging, determining the site and severity of the injury, advising how much unloading is required, identifying what training can safely continue and planning a progressive return to running. These are the keys to management.

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In selected cases we may also consider adjunctive treatments. Low-intensity pulsed ultrasound (LIPUS) has been investigated as a method of stimulating bone healing, although the evidence remains mixed, and studies of bone stress injuries have not demonstrated a consistent improvement in healing or return-to-sport time. We therefore consider it an option in selected cases rather than a substitute for appropriate load management and rehabilitation. Occasionally, particularly with difficult or delayed-healing injuries or concerns about underlying bone health, medication may also be considered.

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Prevention is Still the Best Treatment

Making the diagnosis is only part of the job. We also want to understand why the injury occurred and reduce the likelihood of it happening again. Often there is an identifiable change in training, more kilometres, a longer long run, additional speed work or hills, or several of these introduced together. This is particularly relevant during marathon season.

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Recovery, sleep and adequate fuelling also matter. Increasing running volume without matching the increase in energy requirements can compromise bone health and recovery. Previous bone stress injury, menstrual or hormonal factors, underlying bone health, biomechanics and strength may also need consideration. Collaboration between the physician, physiotherapist and, when required, sports dietitian can be particularly valuable.

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For primary care clinicians, the key message is to maintain a high index of suspicion when a runner develops progressively localised pain, particularly during a period of increasing training load and at a high-risk site. If the clinical picture doesn't quite fit or symptoms aren't behaving as expected, consider whether a bone stress injury may underlie the apparent "niggle". An early diagnosis allows us to determine the site and severity of the injury, establish how much protection if requires and put an individualised rehabilitation programme in place. For runners targeting Auckland or Queenstown, that can sometimes make the difference between losing a few weeks of training and losing the race altogether.