So, what exactly are shin splints?

Shin splints cause pain on your shin bone

Shin splints (medial tibial stress syndrome) causes pain along the distal-third of the posteromedial tibial border

Health Professional? Jump to this article instead.

As a runner, you no doubt have heard countless runners complaining of "shin splints." Maybe you have had them yourself? But, unfortunately, you can't treat your injury without excepting one key fact: shin splints is an umbrella term for numerous injuries. 

If you don't identify the injury you have, you are not going to treat it correctly. 

Why navigating the "Shin Splints" umbrella is IMPORTANT

According to Dr Nat Padhiar, the British Lead Clinician and Team Leader for Podiatry at the London 20112 Olympic and Paralympic games, shin splints is a "meaningless non-specific broad term used by clinicians, athletes and coaches to describe pain in the lower leg and it may prevent patients getting a correct diagnosis and could lead to long-term damage as a result."

So, step one to a more effective treatment program is identifying what injury you have. For example, do you have medial tibial stress syndrome, a stress fracture, chronic exertional compartment syndrome, popliteal artery entrapment syndrome, tendinopathy or another exertional leg pain? Brisbane, Australia, based Sports & Exercise Physician Matthew Hislop compiled an excellent summary table in a study on exertional leg pain.

Table outlining the differences in exertional leg pain

Adapted, with permission, from Hislop (2014) - turn your phone landscape for this one

Breaking Down the Table

Medial tibial stress syndrome (MTSS) has a high incidence rate, affecting up to 42% of the exercising population. It appears in females more often than males and tends to be bilateral, affecting both legs simultaneously. The only time MTSS should hurt when you're not exercising is when you touch along the distal third of the posteromedial tibial border - this is the third of the inside border of your shin bone closest to your ankle. Not on the table is the fact it tends to be sore for about 5cm (2 inches). In addition, it tends to flare up at the start of exercise when you're warming up and again when you finish up. Does this sound like your injury?

What if your leg hurts from the first stride and is only in one leg? The incidence rate of stress fractures of the shin bone isn't well known but tend to be found on one side at a time. The stress fracture doesn't always happen in a similar location as MTSS; it can be elsewhere. Another differentiator from MTSS is the fact a stress fracture is focally sore to touch. 

Chronic exertional compartment syndrome (CECS) is another common injury that falls under the shin splints umbrella. Tending to affect both males and females and present in both legs, this is one of the injuries commonly referred to as "anterior shin splints" when affecting the lateral compartment. A key differentiator for how the pain presents is the crescendo-decrescendo pattern, a slow build-up of pain and slow dissipation after exercising. 

Not shown in this table is how often CECS of the lateral compartment might be overdiagnosed. This was addressed by Dr Andrew Franklyn-Miller in 2014, who termed the condition "biomechanical overload" syndrome. 

Are you confused? The most important thing for you to do is get a thorough diagnosis from a health professional. Each of the above injuries (and popliteal artery entrapment in the table) has varying severities and quite different treatments. So don't waste your time going down the wrong path; get diagnosed correctly the first time around. 

For most, the term shin splints encompass the most common presentation under the umbrella: medial tibial stress syndrome. Therefore, I will focus on this for the rest of the article. 

What is Medial Tibial Stress Syndrome?

As seen above, MTSS is very common in runners. But, does research conclude on what is occurring?

I would like to first open up with the statement: the pathophysiology (what causes the injury) is poorly understood and is often open for debate. There are two common theories: 

  1. Bone Loading
  2. Fascial traction

bone loading

Excessive bone loading due to repeated bending of the tibia is believed to contribute to MTSS. If the shin bone undergoes excessive load, a stress reaction occurs. As a result, the bone cannot remodel or strengthen faster than it is being broken down. If this process continues without the bone having adequate rest to strengthen, then a stress fracture can occur. While early stages are considered pain-free, when the periosteum (thin layer of tissue outside the bone) is inflamed (see below in The Fredericson Classification System), the diffused pain is described. 

The Fredericton classification system for medial tibial stress syndrome

The Fredericson Classification System for MTSS follows the progression related to the extent of the injury: Grade 0 – Normal bone under optimal load, Grade 1 – Initial phases of excessive loading with periosteal oedema, Grade 2-3 – Continued excessive load causing marrow oedema, Grade 4a – intracortical signal changes highlighting more severe deterioration, and Grade 4b – cortical stress fracture 

fascial traction

As early as 1958, the term "shin splints" was linked to a traction injury of the lower leg musculature. The muscles connect to the bone via fascia. Overactivity, weakness or tightness of muscles is believed to pull excessively on attachments to the bone, causing inflammation and pain. 

The three main muscles commonly implicated are the tibialis posterior, the soleus and the flexor digitorum longus (FDL). For this theory to hold firm, these three muscles need to attach to the inside border of the shin bone and along the furthermost third. So, do they?

The tibialis posterior is often believed to be the muscle implicated with MTSS; however, in detailed cadaver studies, it has been shown that the tibialis posterior does not attach to the border of the shin bone. Instead, it has been demonstrated that only the FDL and the soleus muscles originate on the inside border of the tibia. So, do these muscles attach to the shin bone in the third known for being sore? The answer: not always. The most recent study I found shows that the soleus attaches to that site in roughly 33% of males and 72.5% of females. This may contribute to the increased prevalence of injury in female athletes; however, more research is needed into this and the prevalence of soleal attachments along the distal third in other demographics. 

So, what exactly are Shin Splints?

What shin splints are precisely is up for debate. However, we can conclude that MTSS is challenging to treat and takes a long time for the patient to overcome. For example, Moen et al. (2012) demonstrated in an RCT; it takes 90% of patients 250-300 days to recover sufficiently enough to run pain-free for 18-minutes. 

If you'd like to read more on how to treat medial tibial stress syndrome (MTSS) or anterior shin splints, go check out these articles:

About the author:

Ben Lindsay is the Managing Director and engineer behind the Solushin medical device. A former national medalist swimmer, Ben aspires to learn from physicians, physiotherapists and podiatrists so he can develop tools to improve the quality of care for their patients.

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