It’s that time of year where ‘fair-weather’ runners come out of hibernation and marathoners start increasing their mileage.  Even though the weather has been pretty dreadful in Devon this winter, I have definitely noticed more people out running in the last few weeks as I am running or cycling into Exeter for work.  

One of the conditions we see a significant amount of in the physio clinic at this time of year is stress fracture. Stress fractures can range from an irritating niggle to significant life changing bad injury if not managed properly, so here are some important things to understand.  

What is a stress fracture?

If you think about it, all fractures develop due to physical stress so it is a bit of a funny term in a way.  When we talk about stress fractures though, we generally mean small changes to the micro-structure of bone as a result of low level, repetitive loading that eventually causes it to weaken, rather than a one-off sudden, forceful event causing instant damage.

A stress fracture is possibly best thought of as a ‘spectrum disorder’ ranging from something that is barely observable on MRI to bone bruising, inflammation of the periosteum (bone lining) all the way through to an abrupt frank injury where, if not managed properly, continued physical stress, and ignoring the symptoms, can lead to sudden big breaks.

How is stress fracture diagnosed?

MRI is the gold standard imaging technique and only reliable test for diagnosing stress fractures.  An x-ray should not give you reassurance as x-rays are not a reliable investigation for diagnosis even after 6 weeks or so of persistent symptoms.

Can I have a stress fracture and not know about it?

Yes you can.  Stress fractures are actually commonly seen on MRI scans in asymptomatic populations, for example runners who do not report any pain in that area.  Interestingly, the point at which your brain starts to create pain in response to sensory input from our tissues is really quite variable between individuals.  

How does a stress fracture develop?

As with any musculoskeletal tissue, bone undergoes a constant process of cell breakdown and new cell growth or repair.  All cells in your body are dying and being replaced and so, remarkably, in a couple of years from now there will be pretty much none of you left that is here now as you read this blog - weird concept!  There are many factors that go into how quickly bony tissue breaks down as well as the optimal rate of new bone cell formation. These include optimal nutrition, hormonal influences, sleep quality, training volume, age, other medical or physical issues that your body is dealing with at that time as well as body weight, movement efficiency and other biomechanical factors.

The term homeostasis refers to a state where these factors are in balance i.e. the rate of tissue breakdown equals the rate of tissue repair and therefore tissue quality is maintained.  A loss of homeostasis is where there is a net loss in tissue quality.

Does it only affect people who run a lot?

Actually, no.  As the development of stress fractures involves lots of different variables, it may be that running volume is relatively low but all the other factors mentioned above are high and you may still end up being vulnerable.  For example, a relatively low running volume may be accompanied by poor nutrition and sleep quality due to work stress.  

It also doesn’t have to involve running at all.  Any impact type sport could result in a bony stress reaction.

What are the classic features of stress fracture?

Patients will often describe their pain as quite vague, moves around slightly or appears to come and go, especially in the early stages.   Some will say that their pain actually feels like it is in the bone whilst others describe it as a deep ache and are often unable to put their finger on it (for example femoral neck just below the hip joint where the bone is deep and covered in lots of muscle).  Stress fractures are often associated with resting pain, including night time pain.  

Alternatively, it could be in an area where the bone is actually easy to feel as it sits just under the skin.  Obvious examples are the tibia (front of the shin) or metatarsals bones (foot) and patients can usually point clearly at the source of pain.  Particularly in the tibia there may well also be some swelling that is easy to see just under the skin at the front/inside part of the lower leg.  This can become thickened (oedema) where you can literally leave a dent in the soft tissue swelling over the bone after gentle pressure is applied for a few seconds.

Having a sense that you just do not trust your body to take load any more is definitely suspicious and a stress fracture should be considered until ruled out with suitable tests.

How long does it usually take to settle? 

Unfortunately, although bone is a vascular tissue (has a good blood flow) and therefore heels pretty quickly, we are still looking at at least 6 weeks for most stress fractures to settle, often more.  Repeat MRI is recommended as the best indicator of adequate healing. Using pain response with activity is not good enough and athletes often have higher pain thresholds and higher tolerance to prolonged painful stimuli than non-athletic populations.  So patient feedback alone can be unreliable as a marker of repair and therefore as a guide as to when your body is ready to start training again. In practice, however, patients are often just left to rest for an adequate amount of time for bone healing to occur and then encouraged to slowly re-engage in weight bearing activity using pain as a guide as to what they are able to do.

Mostly, patients will be asked to use crutches (stress fractures in the hip and pelvic area) and or walk in a rigid boot (shin and foot) and to minimise weight bearing activity during recovery.  Discuss with your doctor or physio what you can do in terms of physical conditioning whilst you recover as it is important to keep doing something whilst you rest the injured area.

Should patients just rest for a given period of time and then return to what they were doing before?

This is not a sensible approach and often leads to re-injury.  There needs to be a clear understanding of the likely factors that led the patient to this point of having a stress fracture in the first place.

Biomechanical assessment with good physio services who is experienced at looking at runners is essential. If we can help runners to move with greater efficiency, they will place more optimal stress through their tissues.  There are clear skeletal differences and movement inefficiencies that put runners at greater risk of getting a bony stress reaction.

We would encourage patients to assess and then monitor bone density if appropriate (Dexascan) as well as vitamin D levels (blood tests) and to take supplements if they are deficient in the key minerals that give bone its strength.  Eating a balanced diet is vital but sometimes patients have digestive systems that are not able to absorb and use the nutrients that are present in the food that we eat. Seeing someone who really knows about sports nutrition can be a good idea.

Consideration of load volume is important too.  Ensure that training volume and intensity start at an appropriate point again after injury and encourage suitable cross training whilst returning to higher volumes of running (perhaps substitute a fair percentage of your ‘ideal’ running volume for cycling in the short term so that you continue to make good aerobic gains but without upsetting the bone quality.  Strength training is often quite important too and has been shown to improve bone density and strength in all sexes, ages and athletic and non-athletic groups.  

And do not forget the other lifestyle variables that can impact your body’s ability to repair and regenerate optimally.  One of the most important of these is sleep quality as this is when a lot of the repair and regeneration takes place in our tissues.

If in doubt, ask...  I am happy to be contacted with any questions you may have using nick@thegoodphysio.co.uk