Shin splints (medial tibial stress syndrome) causes pain along the distal-third of the posteromedial tibial border
Disclosure: This was written for medical professionals. If you are a runner, why not check out our simpler explanation here
As a medical professional, you no doubt have had a countless number of patients come in complaining of "shin splints." While I will look over the nuisance of them over-utilising Doctor Google for a self-diagnosis, you need to understand what you're dealing with regarding the patient's exertional leg pain. I recently spoke with Nick Knight, a leading musculoskeletal podiatrist from the UK, who said there are upwards of 150 different reasons your shin can hurt!
For most, the term shin splints encompass the most common presentation under the umbrella: medial tibial stress syndrome (MTSS). MTSS will form the primary focus of this blog post.
Why navigating the "Shin Splints" umbrella is IMPORTANT
Shin pain does not necessarily mean medial tibial stress syndrome (MTSS), the most common injury that falls under the umbrella term “shin splints”. This was despite the term originally being coined in 1966 by the American Medical Association as “pain and discomfort in leg from repetitive running on hard surface or forcible excessive use of foot flexors; diagnosis should be limited to musculotendinous inflammations, excluding fatigue fracture or ischemic disorder” (American Medical Association, 1966). However, the term was still being used as a generic term for general pain in the tibia, so the term MTSS was developed in the early 1980s.
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 the patient has. Do they have medial tibial stress syndrome, a stress fracture, chronic exertional compartment syndrome, popliteal artery entrapment syndrome, tendinopathy or another exertional leg pain? Brisbane based Sports & Exercise Physician Matthew Hislop compiled an excellent summary table in a study on exertional leg pain. The site, presentation and pattern of pain is important to help us navigate the differentials of exertional lower leg pain.
Adapted, with permission, from Hislop (2014) - turn your phone landscape for this one
What is Medial Tibial Stress Syndrome?
Medial tibial stress syndrome (MTSS) is an overuse injury that affects 4-20% of the general population and has increased prevalence (35%) in athletes and military personnel.
MTSS is described as "pain felt along the middle or distal third of the posteromedial border of the tibia" (Yates et al., 2004). Furthermore, the pain is aggravated with a weight-bearing activity that gradually subsides upon completion of the exercise. There is also palpable tenderness along the posteromedial tibial border of the tibia for at least 5cm in clinical examination.
In addition to tenderness at palpation, consider a single leg hop test to help distinguish between a stress fracture and MTSS. A patient with MTSS can hop at least ten times on the affected leg, where a patient with a stress fracture cannot hop without severe pain (Batt et al., 1998).
While the pathophysiology is poorly understood and frequently debated, current evidence suggests that MTSS is associated with fascial traction, overloading of the tibia, or a combination of the two (Moen et al., 2009).
I would like to first open up with the statement: the pathophysiology is poorly understood and is often open for debate. In this article, I discuss two common theories:
- Bone Loading
- Fascial traction
Excessive bone loading due to repeated bending of the tibia is believed to contribute to MTSS (Magnusson et al., 2003). If the tibia undergoes excessive load, a stress reaction occurs. Osteoclast activity outweighs osteoblast, leading to osteopenia (Beck, 1998) or "lower bone density". This was also noted by Magnusson et al., who observed reduced bone mineral density in patients with MTSS compared to healthy controls, where the bone density returned to normal as the MTSS symptoms subsided.
Quite simply put, if the stress on the bone is too great or "excessive", then a stress reaction occurs. 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 is inflamed (see below in The Fredericson Classification System), the diffused pain is described.
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
Muscle fibre traction via Sharpey's fibres is shown to result in tibial periostitis at the MTSS injury site (Franklyn et al., 2015). This was not the first time this was hypothesised or demonstrated in a study. As early as 1958 (Devas et al., 1958), the term "shin splints" was linked to a traction injury of the lower leg musculature. However, the traction theory was initially challenged based on the believed fascial attachments to the tibia and the location of pain; the soleus was thought to not attach along the distal-third of the posteromedial tibial border.
Quite often, the tibialis posterior is 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 posteromedial tibial border. It has been demonstrated that only the flexor digitorum longus (FDL) and the soleus muscles originate from the medial aspect of the tibia (Beck et al., 1994, Brown, 2016). This does not necessarily answer the question posed above, does the soleus connect along the distal-third?
In a recent cadaveric study, anatomical variability was highlighted in the male and female gender. In roughly 33% of males and 72.5% of females, the soleus was shown to attach to the distal-third of the tibia (Edama et al., 2015). 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.
While Edama et al. demonstrated anatomical variability in his cadaveric study, Brown (2016) found virtually no muscle attachment to the distal third of the tibia other than the deep crural fascia. Authors have proposed a mechanism whereby excessive activity leads to tension in the crural fascia, which places traction on the periosteum of the tibia (Wallenstein R, 1983, Murbarak et al., 1982).
So, what exactly are Shin Splints?
What shin splints are exactly is up for debate. Evidence suggests shin splints (MTSS) is either bone loading, some form of fasciopathy, or a combination of both. What we do know is, MTSS is often difficult to treat and takes a long period of time for the patient to overcome. 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; so, if what you're doing works, stick with it. The lengthy time should also influence your communication and education strategy for patients.
It was for this reason we designed the Solushin. No more 9-month recovery periods; instead, immediate noticeable reduction in pain with a typical return to a full-load training program within 5-weeks.
Want a free in-service for your clinic?
I currently run free in-services for all clinics which count towards your CPD hours (only confirmed in Australia). If you would like me to run through this all in more detail, please click the link below to book a free time.
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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