Bone Stress Injuries in Runners: When a Niggle Is More Than Just a Niggle
Bone stress injuries are something we see relatively frequently in runners and endurance athletes, and they are an area we have a particular interest in assessing and rehabilitating at SurfEdge. They can also be frustrating injuries, particularly because they do not always present in the way people expect. There is not necessarily a sudden onset of severe pain or a particular run where something obviously goes wrong. Quite often it starts as a relatively innocuous ache through the shin, foot, ankle or hip that appears towards the end of a run and initially settles reasonably quickly afterwards.
This is where recognising the early signs becomes important. Bone stress injuries exist on a continuum, and identifying an injury in its earlier stages can potentially mean a very different rehabilitation process compared with continuing to train until it has progressed to a more significant stress injury or fracture.
What is a bone stress injury?
Bone is living tissue and is constantly adapting to the loads we place upon it. Every time we run, we expose the skeleton to repeated mechanical loading. This is not inherently a bad thing. In fact, appropriate loading is necessary for maintaining healthy bone and stimulating adaptation.
As part of this normal process, microscopic damage occurs within bone and is subsequently repaired through bone remodelling. Problems begin when the cumulative stress being placed upon a particular area starts to exceed the rate at which the body can adequately repair and adapt to it. If that imbalance continues, changes can develop within the bone and progress along a continuum from an early bone stress response through to a more significant bone stress injury and, ultimately, a stress fracture.
This is why we tend not to think of stress fractures as injuries that simply happen on one particular run. In many cases, the process has been developing for some time before the athlete becomes aware of it.
It's not necessarily as simple as running too many kilometres
One of the first things runners tend to look at when they develop an injury is their weekly mileage, and sudden increases in running volume are certainly relevant. However, kilometres alone don't tell us the whole story.
Running intensity is also important. Increasing the amount of speed work, adding hills, racing more frequently or changing the type of terrain you're running on can substantially alter the forces being placed through the body without necessarily producing a dramatic change in total weekly kilometres. An easy 10 km run and a hard 10 km session are not equivalent in terms of the mechanical stress placed through the skeleton.
There can also be a delay between changes in training and the onset of symptoms. When we assess someone with a suspected bone stress injury, we therefore want to know more than what they did in the few days immediately before the pain appeared. We will often look back over the preceding weeks and consider changes in overall volume, intensity, frequency, terrain, racing and recovery. Sometimes the relevant change is quite obvious once we go looking for it, but in other cases there is no dramatic training error at all.
What do bone stress injuries feel like?
The early symptoms can be surprisingly subtle. Initially, an athlete may notice an ache after running or towards the end of a longer session. If the problem progresses, the symptoms may start appearing earlier during runs, take longer to settle afterwards, or eventually become noticeable with walking and normal day-to-day activity. More advanced injuries can sometimes become symptomatic at rest or overnight.
The behaviour and location of the symptoms are often more useful to us than the pain score alone. A bone stress injury does not necessarily need to be extremely painful, particularly in its earlier stages, and relatively significant injuries can occasionally present with fairly modest symptoms.
We also pay attention to how localised the pain has become. A very focal area of bony tenderness can raise our suspicion of a BSI, although this needs to be interpreted alongside the rest of the examination rather than used as a diagnosis in isolation.
Shin pain is a good example of this. Medial tibial stress syndrome, commonly referred to as shin splints, will often produce a more diffuse area of tenderness along the posteromedial tibia. A tibial bone stress injury may be considerably more focal. There can, however, be overlap between the two presentations, which is why simply assuming that all exercise-related shin pain is "shin splints" can occasionally cause problems.
The location of the injury matters
One of the most important considerations with a suspected bone stress injury is exactly where it is located. Not all BSIs carry the same prognosis or level of risk.
Some locations are considered relatively low risk because they generally have favourable healing characteristics when the load is appropriately managed. Other sites are considered high risk because of factors such as their blood supply, the mechanical forces acting across the area or the consequences if the injury progresses.
This distinction has a significant influence on how conservatively we manage the injury, whether further imaging or medical assessment is required, how much weight-bearing or sporting activity we are comfortable maintaining, and how quickly rehabilitation can progress.
For this reason, two runners who both have a "stress fracture" may receive very different advice. The severity of the pain is only one small part of the clinical picture. The anatomical location, severity of the injury, symptom behaviour and individual athlete all need to be considered.
Why did the bone become overloaded?
Sometimes the answer is relatively straightforward. There has been a significant increase in training volume, more speed work, an increase in racing or a major change in the athlete's usual training.
In other cases, the training history doesn't immediately explain why the injury has occurred. This is where we need to look beyond the injured bone itself.
Ultimately, a bone stress injury represents an imbalance between the load being applied to the skeleton and the capacity of that skeleton to tolerate and adapt to it. Training determines one side of that equation, but the athlete's underlying capacity determines the other.
Previous bone stress injuries, strength and conditioning history, nutrition, energy availability, hormonal health, sleep, recovery, medications and underlying bone health can all be relevant. Life stress can also contribute indirectly by affecting recovery, sleep and an athlete's ability to adequately fuel around training.
Energy availability is particularly important in endurance athletes. An athlete needs enough energy not only to complete their training but also to support normal physiological function and recovery. If energy intake consistently fails to meet those combined demands, the body begins making compromises, and over time this can negatively affect hormonal function and bone health.
Importantly, this can occur in both male and female athletes and is not limited to athletes who are underweight or who have an eating disorder. Sometimes it is simply a case of someone training significantly more than they realise without increasing their fuelling sufficiently to match those demands.
Depending on the presentation, management may therefore involve more than physiotherapy alone. We may recommend involvement from a GP or sports physician and, where appropriate, an experienced sports dietitian to ensure the factors contributing to the injury are properly addressed.
A history of previous bone stress injury is also something we take seriously. Having sustained a BSI previously increases the risk of another, and recurrent injuries warrant a closer look at why they continue to occur. Repeatedly resting until the pain disappears and then returning to the same training environment without addressing the underlying contributors is unlikely to solve the problem long term.
When is imaging useful?
Not every running injury requires imaging, and in many musculoskeletal presentations a good history and clinical examination will give us enough information to begin appropriate management. Suspected bone stress injuries are one situation where imaging can be particularly useful when the clinical picture warrants it.
MRI is generally the preferred imaging modality when investigating a suspected BSI because it can detect changes within the bone that may not be apparent on a standard X-ray, particularly earlier in the injury process. Imaging can also help establish the extent of the injury, which can be useful when determining prognosis and planning rehabilitation.
Our threshold for recommending imaging will vary depending on the presentation. If the location raises concern for a high-risk BSI, we are going to be considerably more cautious than we might be with a typical low-risk presentation.
Rehabilitation involves more than simply resting
Once a bone stress injury has been identified, the first priority is reducing the stress through the injured area sufficiently to allow the bone to recover. The amount of unloading required depends on both the site and severity of the injury. Some athletes may only need their running modified, while others will require a much more substantial period of unloading.
What we don't want to do is treat this as a period where the athlete simply stops everything and waits.
There is usually plenty we can continue working on throughout the rehabilitation process. Depending on the injury, we may be able to maintain cardiovascular fitness through alternative training, continue strengthening unaffected areas, address strength deficits and begin preparing the rest of the body for the eventual return to running.
As the bone becomes ready to tolerate more load, we progressively reintroduce it. This is an important part of rehabilitation because our end goal is not simply for the athlete to become pain-free. We need the injured bone to regain sufficient capacity to tolerate running again.
Returning to running after a BSI
Return to running should be treated as a progression rather than a single milestone. Being able to complete one pain-free run does not necessarily mean the athlete is ready to resume their previous training program.
Depending on the injury and the athlete, we may initially use controlled run-walk intervals before gradually increasing continuous running exposure. Volume is generally rebuilt before we start introducing substantial amounts of intensity, because faster running, hills and harder sessions place greater mechanical demands on the skeleton.
This distinction is important. An athlete may be perfectly comfortable running easily while still lacking the capacity required for intervals, racing or their previous peak training load.
Strength training also forms an important part of this process. Runners are exposed to enormous amounts of repetitive loading through their sport, but running alone does not necessarily provide all of the stimulus we want when rebuilding overall physical capacity. Progressive resistance training, followed by appropriately prescribed jumping, hopping and other higher-load activities where suitable, can help prepare both the athlete and their skeleton for the demands they need to return to.
Recovery is part of the training program
One of the recurring themes we see with endurance athletes is an excellent ability to plan training and a much poorer ability to plan recovery.
Training provides the stimulus for adaptation, but the adaptation itself occurs afterwards. This applies to the cardiovascular system, muscles, tendons and bone. If we continually accumulate training stress without allowing sufficient recovery, fuelling and time for tissue adaptation, eventually the balance between load and capacity can shift in the wrong direction.
For that reason, planned easier weeks, adequate sleep, sufficient nutrition and sensible progression of training aren't separate from the training program. They are part of it.
The bigger picture with bone stress injuries
Bone stress injuries are rarely as simple as someone having "run too much". In most cases, we are looking at the interaction between the amount and type of load being placed through the skeleton and the athlete's capacity to tolerate and adapt to that load.
Good rehabilitation therefore needs to address both sides of the equation. We need to understand what has happened with training, where the injury is located and how significant it is, but we also need to consider previous injury history, strength, recovery, fuelling, bone health and the demands the athlete eventually needs to return to.
At SurfEdge Sports Physiotherapy, this is how we approach bone stress injuries. The aim isn't simply to settle the pain and send someone back out running. We want to identify the factors that contributed to the injury, maintain as much physical capacity as is safely possible during recovery, progressively rebuild the injured bone's tolerance to load and ultimately return the athlete to their normal training and competition demands.
If you've developed localised bone pain with running or sport, particularly if it is starting to occur earlier during exercise, lingering for longer afterwards or becoming noticeable with walking or everyday activity, it is worth having it assessed rather than continuing to push through it.
SurfEdge Sports Physiotherapy provides assessment and rehabilitation for bone stress injuries and running-related injuries, including progressive strength and conditioning and return-to-running planning.
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