Beyond the Stress Fracture

A quick look on Pubmed (a database of research papers) for a search term like ‘stress fracture’ will yield close to 100,000 results. Whilst it’s great that so much research has been done, it’s daunting, overwhelming and easy to get confused by the sheer amount of information out there.

In the post below, I describe my personal experience with stress fractures, discuss how age and sex affect the likelihood of developing one, and most importantly, reflect on what changes could be made to support amateur and recreational athletes in preventing and managing these injuries.

My experience:

In March 2025, I was diagnosed with ‘bilateral posterior tibial grade 4a stress fractures’. There wasn’t much more information given to me than that, other than to get in touch with a fracture clinic ASAP. Fairly clueless on the matter, I took to Dr Google (never reccomended) and understood this diagnosis to mean that fracture lines were present on my MRI, but that I hadn’t completely broken my legs. Although I felt initially relieved to hear that my tibia(s) weren’t yet split in half, that relief quickly subsided, and turned to exasperation at the lack of clarity I had on the whole situation. I had no clue on causes, healing times, treatment, and had a sense of despondency toward the whole thing, given the diagnostic process I went through in itself.

It all started toward the end of January 2025, coming off the back of a 45 minute 10km run. I was absolutely ecstatic, after a winter plagued with illness, it was the fittest I’d felt in a long time, and I felt like I had so much more to give. A few days later, I started getting pain in my right shin; nothing major, just a slight twinge now and then. Deep in training for Manchester marathon, and off the high of a PB, I wasn’t going to let a minor inconvenience stop me running the miles. Like most amateur athletes I know, I ignored it, thinking I’d just overdone it slightly. Fast forward to the start of March and the pain was still there, a 3/10 at most, but becoming ever apparent now during walking, not just running. Still ignoring it, I can pinpoint the exact moment I realised it may be time to address the elephant in the room – or more accurately, in the shin. After a chilled weekend away with my friend, I tried to end our holiday with a really easy 5km run around the beautiful Lake Annecy. When I physically couldn’t bring myself to run without agonising pains shooting up my calf, I knew something wasn’t right. Still, the competitive, stubborn side came out and I got home, rested for a day, and then tried to run a 30km. I made it to 22km before pulling the plug.

The next day, I got up for work and couldn’t bear any weight on my right leg. My calf felt like it was being severed in half, and I felt an almighty weakness throughout my entire leg. After a childhood of playing football, running and getting involved in pretty much any sport available, I’ve had my fair share of experience with soft tissue injury. I knew with almost certainty that this was bone.

A short trip to A&E yielded nothing. I had my shin pressed in one place, my achilles stretched, and was subsequently told for a fact that this was a soft tissue injury. I was told that the best course of action was to keep it moving and that no imaging was needed because it was just a muscle tear… Working in the public sector myself, I have nothing but admiration and utmost respect for all NHS staff, but on this occasion I felt my concerns were dismissed entirely. The next day, the pain was worse and I went to my GP. He referred me for an X-Ray and suggested an MRI would be most appropriate – with a preface that the waiting list was upwards of 12 weeks.

A very long, and expensive story cut short, I ended up paying privately for an MRI. My X-Ray showed a healing fracture of the fibula neck, yet, I was still adamant something was wrong with my tibia. Results came back from the MRI and confirmed the bilateral stress fractures.

Six months down the line and my rehab is still only just finding it’s feet. After no running for 4 months, I went out the blocks, slowly, but fully expecting to be pain free. It was a quick and humbling realisation that this wouldn’t be the case. I’m slowly accepting it could be months before my legs are up to running double digits again, and I’m learning to be patient, embrace the slowness, and pouring my energy into swim, bike and strength.

What this has given me though is an insight into one of the major issues facing amateur and recreational athletes. I was in an extremely priveleged position to be able to pay for an MRI and get back accurate results, but this isn’t, and shouldn’t have to be the case for everyone. I’ve spent a long time considering the risks had someone walked out of a&e and ‘kept moving’. A long time wondering what more can be done to support amateur athletes.

The Science of Stress Fractures

What is a stress fracture?

A stress fracture is an overuse injury affecting bones. They occur when the mechanical pressure caused by repeated motions (such as running) is greater than the ability of a bone to regenerate. In essence, the bone cannot adapt at the speed at which it accumulates damage.

To understand the risks of developing a stress fracture, it’s important to understand two biological functions within the body.

Strain adaptive bone remodelling: This principle is simple in theory, more complex in nature. Reserach has shown that physical activity naturally causes small-scale deformation in bone tissue. This is picked up by tiny sensors, called osteocytes. If load is sufficient, osteocytes trigger osteoblasts, specialised cells that lay down collagen – the base material for bone. Simply put, on the whole, increasing the load increases the activity of osteoblasts, increasing the bone mass and therefore bone strength.
The reverse, however, is also true. If load on the bone is reduced, osteocytes trigger osteoclasts, specalised cells that act to break down and reabsorb bone tissue. This in turn reduces bone strength.
Microdamage repair: During physical activity, it’s very normal for bones to get microscopic cracks in response to repeated load. In most instances, where microdamage has occurred, osteocytes will send out signals to osteoclasts to break down the ‘cracked’ bone, and later, osteoblasts to lay new bone in it’s place.

A stress fracture occurs when these mechanisms can’t keep up with the mechanical load. That is, repetitive stress exceeds the speed at which the bone can remodel, and inadequate recovery time prevents microdamage being repaired. Together, this leads to an accumulation of damage, which leads to weaker bone, which eventually leads to stress fractures.

Non-Modifiable Risk Factors for Stress Fractures

Taking into account the above, we’re all susceptible to stress fractures if we increase load too fast, or neglect recovery time. Biomechanics, training techniques, strength training and nutrition are crucial to get right – all which will be covered in another blog. For the focus of this, however, I’m diving into how some uncontrollable characteristics – age and sex – disproportionately increase the risk of developing a stress fracture.

Sex

Research has established the biological female sex are disproportinately affected by stress fractures in both the general population, and in professional athletes. One piece of research, a 2022 US nationwide study of stress fractures showed that women had a higher chance of developing a stress fracture in every age group, other than in under 14s. There’s a few major factors evidence points to, with hormonal difference a major one. Estrogen, a hormone, regulates bone density by suppressing osteoclast activity, and promoting osteoblast activity therefore, preventing bones from breaking down and supporting remodelling activity. The case is true in males, with their estrogen produced from the naturally produced hormone testosterone.

So why are females at a disadvantage? Well, women are far more likely to experience estrogen deficiency than men. Disruptions to the menstrual cycle (amenorrhea) are a causal factor of low estrogen. Although relatively uncommon in the general population, research has shown levels of amenorrhea to be far higher in (amateur) athletes than the general population. For example, one study concluded that of the sample (128 female track and field athletes) 30% had an irregular menstrual cycle at one point in the 4 year study period. In a similar vein, females naturally go through the menopause, a time at which estrogen levels decline rapidly, and bone mineral density has been shown to decrease. Further, contraception which suppresses ovulation such as the progesterin injection, contraception containing synthetic estrogen such as the combined pill and medication for endometriosis can all contribute to low estrogen levels, putting females at a heightened risk. In general, linked to estrogen deficiency, epidemiological studies suggest females have a 1.5 to 2 times higher likelihood of developing a stress fracture.

Additionally, studies have shown that most males have a higher bone circumference after puberty than their female counterpart; with this anatomical difference contributing to higher bone strength. Cortical bone, the outer layer, provides a lot of mechanical strength and protects the inner bone. In females, this layer is often upwards of 10% thinner than in males, and is therefore more susceptible to microdamage, and has less overall strength.

Age

Another non-modifiable risk factor, age. Unlike many things, the correlation between age and stress fracture risk does not appaear to be a linear relationship. The general consensus of research is that that those under 25 (although some studies will argue under 20) have an increased risk of developing a stress fracture, as peak bone mass and mineralisation will not have yet been met. This means that bones are structually weaker and more suscpetible to stress put through them, especially in periods of growth spurts whereby the cortical bone tends to be thinner. In a behavioural sense, research would suggest that under 25s are more likely to have higher intensity treaining regimes, therefore overloading the bone and inadequately recovering, coupled with an underdeveloped nutritional stategy – which will be discussed in a later blog.

There’s also an increased risk of stress fractures in the over 50 population, with correlational links to lower bone mineral density, caused naturally as estrogen and testosterone levels decline with age, or artificially through the increased likelihood of taking medication for comorbidities, that indirectly lowers bone mass density. In general, the body’s ability to repair slows with age, therefore, increasing the vulnerability for microdamage to progress into something more serious, if repeated load is placed through the bone. In a behavioural sense, correlational studies have shown that the older population have a higher chance of a sedentary lifestyle, whereby the body adapts to the reduced load, increasing osteoclast activity, decreasing bone strength, and increasing the vulnerability for bone damage if activity is suddenly increased.

What does this all mean?

Well, age and sex by no means encompasses the only risk factors in developing a stress fracture. They don’t even touch the surface. As well as biomechanics, nutrition and training techniques, which will be covered separately, use of non-steroid anti-inflammatory drugs, excessive caffeine intake, cold weather, psychological stress, smoking and dehydration are all implicated in increasing the risk of developing a stress fracture, as are many more. All of this to say, stress fractures are multi-factorial, unlikely to be caused by one factor, but influenced by many.

So…why did I get a stress fracture?

A question with a fairly simple answer now I’ve turned to the science. To start with, I’m female, I was under 25 when diagnosed, and I increased the load of my training dramatically in a short period of time. Practically hit the jackpot in the reasons outlined above. Although I’m entirely to blame for my neglect of strength training and poor training plan, my sex and age were out of my control. I had absolutely zero idea just how much my risk increased just by being a 24 year old female. Not to mention, a 24 year old female who was a highly competitive, driven, amateur runner. So that got me thinking…

What policy changes would support amateur and recreational athletes at high-risk of a stress fracture?

Are training programs built around male norms?

The short answer is yes. Historically, training programs such as those in the military were built around healthy, cisgender, male physiology. From brief discussion earlier, it’s clear that men are at an advantage for withstanding higher mechanical load, not to mention, typically having higher muscle mass which act as a ‘shock absorber’ for bones, in some instances. Many programs, especially in amateur/junior sports have fixed progression rates; weekly miles are increased the same for males and females or training intensity is encouraged at the same level. More than most people, I love the idea of women being treated equally in sport. And don’t get me wrong, we are seeing huge changes. But there’s a reason why female footballers have an injury prevelance rate far surpassing the men, it’s because programs have been built for men, by men. It’s a clear issue and one that needs to be addressed before too many young (amateur) athletes do irreversible damage to their body in an attempt to meet unsuitable standards that have been set based on male physiology.

The first logical step would be to see sex-specific progression models rolled out across sport at all levels. We need coaches at all levels to be educated on sex-specific differences, especially in high-impact sports like running. We need female specific pre-conditioning to address naturally weaker areas, and support bone remodelling and muscle mass. We need more education, openness and awareness that differences in males and females are expected, but that it doesn’t make a woman weak for needing more recovery time, or for running 10 miles instead of 12. It makes healthy, happy, strong, supported athletes.

We also need to stop shying away from the topic of menstruation. In general life, but in sport, it can’t be ignored. Menstrual education is so important. Almost every cisgender female has had, or will have a period, and we shy away from talking about this like it’s a secret. The impact of estrogen deficiency in sport spreads far, far wider than stress fractures. More education and support is a must. Female athletes, amateur or professional need safe places where they feel comfortable to discuss menstrual dysfunction – such as a missed period – and most importantly, they need to be listened to and see a resultant change to their training program.

Diagnostics for amaetur/recreational athletes

As I reflect on my own diagnosis, I realise we have a huge issue here too. Non-elite athletes don’t have access to many accurate diagnostic tools when it comes to stress fractures. Often, X-Rays dont pick them up, and a private MRI will set you back over £300, so in most cases, it simply isn’t an option. Although an exact figure isn’t known, it’s estimated that the majority of stress fractures go undiagnosed for a prolonged period, and in some cases, lead to irreversible bone damage.
Rather than a one-size fits all approach like I was met with in a&e, which went something like, ‘it doesn’t hurt to touch, it isn’t a fracture’, shouldn’t all personnel in relevant roles (a&e nurses, school nurses etc) recieve education on stress fractures, their risk factors and the incidence rate among amateur athletes? Low-cost screening procedures like a simple questionnaire about activity, or menstrual health (where applicable) would be time-effective, cost-effective and help identify high-risk cases where the person presents with an injury that could be a stress reaction.
I try to remember the first time I heard about stress fractures, and I think I was 22. Which is saying something, given I did a degree in biology and a public health masters, part of multiple youth sports clubs, and not once was this discussed. It’s beyond concerning that so many young people are at risk of doing irreversible damage to their bodies, but with simple education and slight improvements to diagnostic policy, there’s an opportunity to make a huge difference. Early identification, intervention and awareness can prevent these injuries, and ensure that all amateur athletes can reach their potential.