Pain along the inside of the shin is oneof the most common injuries affecting runners and field sport athletes. It isestimated to affect between 4% - 35% of runners.1 Often labelled as"shin splints," medial tibial stress syndrome (MTSS) is frequentlymisunderstood, leading many to simply rest until the pain settles beforereturning to training, or, push through the pain - only for symptoms to worsen.Current evidence suggests MTSS is not simply an inflammatory condition, butrather an early bone stress injury that develops when the tibia is exposed tomore load than it can adapt to.2 If identified early and managedappropriately, most athletes make a full recovery. However, if ignored, MTSScan progress along the bone stress continuum towards a tibial stress fracture.
Understanding why MTSS develops, andaddressing the contributing factors is essential for successful rehabilitationand reducing the risk of recurrence.
ANATOMY,PHYSIOLOGY AND THE BONE STRESS CONTINUUM
The tibia (shin bone) is one of theprimary load bearing bones of the leg. Every stride, take-off and landingplaces considerable forces through the tibia. These forces are not inherentlyharmful. In fact, they help to make bones thicker, and therefore stronger. This occurs through a process of bonebreakdown and then remodelling, an adaptation that makes bone more resilient.This is best described by Wolff’s Law - the principle that bone remodelsaccording to the mechanical loads placed upon it. Appropriate loadingstrengthens bone; excessive loading without adequate recovery has the oppositeeffect. During running, the tibia experiences several times body weight withevery step, resulting in thousands of loading cycles during a typical run. Whenthese repetitive loads accumulate faster than the bone can remodel, symptomsdevelop. However, this occurs from a combination of multiple factors.3
Tipping into “overload” rarely occurs dueto one single cause. Instead, it reflects the interaction between an athlete's intrinsiccharacteristics and the external loads placed upon the tibia. Whilesome risk factors cannot be modified, many can be identified and addressedduring rehabilitation.
Intrinsic factors include previous bone stressinjuries, reduced calf or lower limb strength, altered running mechanics,limited ankle mobility, low energy availability, vitamin D deficiency andinadequate recovery. Collectively, these factors may reduce the bone's abilityto tolerate repetitive loading.4
Extrinsic factors relate to the stresses applied tothe body. Sudden increases in running volume or intensity, returning to sportafter time away, changes in footwear, harder running surfaces and large volumesof sprinting or jumping all increase the mechanical demands placed on thetibia.
Ultimately, training load is the mostmodifiable risk factor. Successful rehabilitation focuses on identifying whichfactors are relevant to the individual, rather than assuming every case of MTSSdevelops for the same reason.
The Fredericson classificationhelps to conceptualize where one may sit on this continuum based on MRI.5MTSS seems consistent with grades 1-2, where we see changes around theperiosteum, the outermost layer of the tibia. It is around this point thatpeople experience diffuse, aching pains along the tibia. Left unmanaged, thiscan then progress into grades 3-4, where bone breakdown becomes prominent inthe deeper layer of bone. Once a breach is seen from superficial to deep, thisbecomes consistent with a stress fracture. It is important to note, however,that periosteal edema does not diagnose MTSS - as there are people who haveedema on MRI, but have no pain.6 Clinical findings must align todetermine the diagnosis.
CLINICALASSESSMENT & IMAGING
The diagnosis of MTSS is very much aclinical diagnosis, with an MRI best used to support and classify on the bonestress continuum. Clinical assessments generally include a combination offunctional testing - that is, the ability to load through the calf, toleranceto jumping, hopping, as well as palpating the sensitive area. MTSS is generallyfelt on the posteromedial aspect of the tibia, and typically has a length >5cm. If the sensitive area sits more anterior, and has a smaller radius <5cm, then there may be suspicion of a tibial stress fracture.2 AnMRI would be warranted in this case.
When looking through a broader lens,consideration is also given to running mechanics and local as well as proximalstrength and endurance. Research suggests that an increase in duration inpronation during stance, as well as contralateral hip drop may predispose toits onset. A prospective study on cross country runners found that every 1%increase in pronation duration increased the odds of developing MTSS by 1.38x.7
THE OUTLOOK - NOTALL DOOM AND GLOOM
The outlook of MTSS is excellent whenidentified early.
Athletes are generally able to continuerunning during this time with modifications to their running plan, so long aspain remains stable and does not worsen over 24hrs. If worsening, then thiswould be a sign that you are pushing beyond what the bone can cope with.Continuing to train in this manner significantly increases the risk ofprogression to a stress fracture. For context, a tibial stress fracture,particularly the anterior aspect is considered a high riskfracture, as it does not have a great blood supply and therefore heals at aslow rate. These injuries would require several months away from running andsport.
Pain is rarely the problem itself. It isthe body's signal that the current training load exceeds the bone's presentcapacity. Rehabilitation therefore focuses on increasing capacity rather thansimply eliminating pain.
REHABILITATION
Rehabilitation for MTSS, put simply, isabout preventing the bone from progressing through the bone stress continuum,and by providing enough of a stimulus to develop a stronger bone. Bone adaptspositively to progressive mechanical stress, provided the loading isappropriate. Rehabilitation therefore aims to prevent progression along thebone stress continuum while gradually rebuilding capacity for running.
MANAGE TRAININGLOADS
The first step is reducing the amount ofstress placed on the tibia to a level it can tolerate. Complete rest is rarelynecessary. Instead, modifying running volume, frequency or intensity oftenallows symptoms to settle while maintaining enough stimulus for ongoing boneadaptation. Cross-training can also be used to preserve cardiovascular fitnesswhile temporarily reducing repetitive tibial loading.
BUILD CAPACITY
As symptoms improve, attention shiftstowards addressing the factors that contributed to the injury. Progressivestrength training targeting the calf complex, lower limb and trunk improves thebody's ability to absorb force, while gradually reintroducing impact throughhopping, plyometrics and running helps stimulate bone remodelling.
PROGRESSIVERETURN TO RUNNING
Running should be reintroduced gradually,beginning with walk-run intervals before progressing to continuous running,longer durations and eventually faster speeds or sport-specific training. Painshould remain mild (generally ≤3/10) and return to baseline within 24 hours.Rehabilitation should always be guided by symptoms and function rather thanarbitrary timelines.
CONCLUSION
MTSS is far more than simply “shinsplints”. It represents an early bone stress injury that develops when loadingexceeds the bone’s ability to adapt. The goal of rehabilitation isn't to avoidloading the tibia, it is to restore its ability to tolerate it. When trainingload is progressed appropriately and the underlying contributing factors areaddressed, bone adapts remarkably well, allowing most athletes to return torunning stronger and more resilient than before.
References
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- Moen M, Tol J, Weir A, Steunebrink M, Winter TC. Medial Tibial Stress Syndrome. Sports Medicine. 2009;39:523-546. doi:10.2165/00007256-200939070-00002
- Matijevich ES, Branscombe L, Scott LR, Zelik K. Ground reaction force metrics are not strongly correlated with tibial bone load when running across speeds and slopes: Implications for science, sport and wearable tech. PLoS ONE. 2019;14. doi:10.1371/journal.pone.0210000
- Becker J, Wu W. Factors Contributing to Medial Tibial Stress Syndrome in Runners: A Prospective Study. Medicine & Science in Sports & Exercise. 2018;50:2092–2100. doi:10.1249/mss.0000000000001674
- Franklyn M, Oakes B. Aetiology and mechanisms of injury in medial tibial stress syndrome: Current and future developments.. World journal of orthopedics. 2015;6 8: 577-89 . doi:10.5312/wjo.v6.i8.577
- Craig DI. Current Developments Concerning Medial Tibial Stress Syndrome. The Physician and Sportsmedicine. 2009;37:39 - 44. doi:10.3810/psm.2009.12.1740
- Becker J, James S, Wayner R, Osternig L, Chou L. Biomechanical Factors Associated With Achilles Tendinopathy and Medial Tibial Stress Syndrome in Runners. The American Journal of Sports Medicine. 2017;45:2614 - 2621. doi:10.1177/0363546517708193