I can't remember why, but I was reading an article
on WebMD when I saw a sidebar linking to a sports injury quiz. Since a large part of what I do every day is
working to get to the bottom of running injuries, I decided to check it
out. Though most of the questions were
about traumatic injuries to the upper body, which are much more common in
contact sports, there were a few on running injuries. I'm pretty used to seeing misconceptions all
over the place when it comes to the causes and optimal treatments for running
injuries, but one slide bothered me because a) it was so aggressively incorrect
and b) WebMD content is supposed to be vetted and approved by a medical doctor,
which lends it an air of authority.
I've reproduced the offending slide below:
The available answers, by the way, were "torn
ligaments," "inflammation," "tiny fractures," and
"all of the above," none of which are wholly satisfactory.
As readers who have perused my Injury Series articles will know, "shin splints" is a vague term that usually
refers to medial tibial stress syndrome, which is a well-defined problem that
occurs on the medial edge of the tibia (your shinbone). Unfortunately, the term "shin splints"
has morphed into a catch-all term for any exercise-related pain in the
shin. WebMD's picture of an athlete
icing the lateral side of the upper shin certainly doesn't help. The equation of "shin splints" to
"shin pain of any sort" causes mundane things like shin muscle
fatigue and more serious things like anterior compartment syndrome to be
conflated with medial tibial stress syndrome under the improperly-used umbrella
term of "shin splints."
Worse, the answer—"inflammation of muscles,
tendons, bone, and other tissue surrounding the shin bone"—is demonstrably
incorrect. Though the main purpose of this post is to address the larger issue
of outdated or simply incorrect information about running injuries that's all
over the place on the internet, I should be thorough and formulate a more proper
answer to the question of what "shin splints"—understood to be medial
tibial stress syndrome—are caused by.
***
Swiftly stated, shin splints (understood to be
medial tibial stress syndrome) are the result of localized areas of low bone
density in the tibia itself. There is no
significant involvement of the muscles or tendons surrounding the shin, and
only partial involvement of the periosteum, the "skin" that surrounds
the tibia bone.1 Exposure to high-impact exercise like running
strengthens your bones over time, but in order for this to happen, your bone
tissue needs to be remodeled first. This
creates small, localized pockets of low bone density. It's just like remodeling your kitchen:
before you get to work, you need to tear out a few walls. This is a normal phenomenon that's observed
in healthy runners in training.
But when this occurs too fast (as is often the
case in novice runners or people with very ambitious training plans), this
localized loss of bone density is amplified and causes pain. A masterful review study by Moen et al.
outlines four reasons why overloading of bone tissue in the tibia is the best
explanation for shin splints:1
1) Bone scans of runners with shin splints show
abnormalities in the bone and periosteum
2) CT scans of runner with shin splints show areas
of low bone density, which also occur to a lesser extent in healthy athletes in
training
3) MRI scans of runners with shin splints display
abnormalities in the bone and periosteum
4) Bone mineral density is lower in athletes with
shin splints, and returns to normal after they are healthy again.
There is also convincing evidence that directly
refutes the "soft tissue inflammation" theory: anatomic studies of
the lower leg show that the insertion points of the muscles most often blamed
for "pulling" on the tibia don't actually occur at the most common
site of shin pain, one third of the way up from the ankle on the medial edge.2 Further, computational modeling of the areas
of greatest mechanical stresses on the bone during the "active" phase
of gait do correspond to where shin
splint pain is most common.3
***
Now, it's unfair to criticize WebMD too
heavily. You'll find the same type of
misinformation about running injuries all over the internet and in books and
other medical literature as well. But
the question I'm grappling with is this: why are so many websites and resources
for runners so inadequately informed on even the most common running injuries?
In many ways, it's easier to forgive
doctors and PTs who still believe that shin splints are caused by muscle or
tendon inflammation—they learned about injuries a long time ago, perhaps back
when that was the best available
theory. And medical professionals don't
always have the time to peruse through the latest scientific research. But someone
should be doing this. If a DIII runner with a bachelor's in chemistry figure
all this out, you'd think that a place like WebMD or About.com or the Mayo Clinic
would be at least be somewhat keyed-in on what the current scientific opinion
is.
Unfortunately, you'd be wrong. What appears to happen instead is every
website saying more or less the same (incorrect) thing. Let's have a look:
SportsMedicine.About.com
|
MayoClinic.org
|
MedicineNet.com
|
WebMD.com
|
Shin splints generally
occur after cumulative stress causes microtrauma to the soleus muscle at the
point of attachment to the shinbone. Repetitive stress can also cause
irritation of the posterior tibialis muscle and inflammation of the
periosteum, the connective tissue that covers the tibia.
|
Medically known as medial
tibial stress syndrome, shin splints often occur in athletes who have
recently intensified or changed their training routines. The muscles, tendons
and bone tissue become overworked by the increased activity.
|
Shin splints are injuries
to the front of the outer leg. While the exact injury is not known, shin
splints seem to result from inflammation due to injury of the tendon
(posterior peroneal tendon) and adjacent tissues in the front of the outer
leg.
|
[Shin splints] can be caused by: *Irritated and swollen muscles, often from overuse *Stress fractures, which are tiny breaks in the lower leg bones *Overpronation or ''flat feet" -- when the impact of a step makes your foot's arch collapse |
I want to emphasize that all four of these sources claim their articles are reviewed by doctors
or other medical experts! And unfortunately, I'm not just cherry-picking
from specific websites or specific running injuries. The internet (and books for public
consumption, for that matter) are woefully inadequate when it comes to the
causes, risk factors, and optimal treatments for pretty much every running
injury that I have researched.
It is certainly true that two major motivations
for health information websites are to 1) make ad revenue and/or 2) get you to
go see a doctor, which is indirectly a revenue stream as well. For
fun, try searching Google for "heel pain [name of your state or city]"
for a taste of the kind of aggressive "information marketing" that
the medical community is prone to. But I
think the problem runs deeper than this.
There appears to be a disconnect between the scientists doing the
research and the people (runners, doctors, and so on) the research can benefit
the most.
I don't have any answers on how to bridge that gap
just yet. Expecting new biomechanical or
medical discoveries to trickle down on their own to broader audiences doesn't
seem to be working. Until there are some
solutions to this, I'd be irresponsible not
to caution runners against trusting what they read on general medical
websites like the ones in the table above.
I don't think there's any malicious intent, but there isn't an incentive
for academic rigor in citing the information on these web pages and keeping it
up to date, and too much of their information is just plain wrong—often in a
harmful way.
Worse, this sort of thing makes me question if
these kinds of websites are up to date on the kinds of really important medical questions that people go searching the
internet about. I certainly hope not. But then again, how do I know?
References
1. Moen, M. H.; Tol, J. L.;
Weir, A.; Steunebrick, M.; De Winter, T. C., Medial tibial stress syndrome: a
critical review. Sports Medicine 2009, 39 (7), 523-546.
2. Beck, B. R.; Osternig, L. R., Medial
tibial stress syndrome. The location of muscles in the leg in relation to
symptoms. Journal of Bone and Joint
Surgery 1994, 76 (1057-1061).
3. Franklyn, M.; Oakes, B., Tibial stress
injuries: aetiology, classification, biomechanics and the failure of bone. In An international perspective on topics in
sports medicine and sports injury, Zaslav, K. R., Ed. Intech: 2012; pp 509-534.
Don't bother going to physiotherapists. Mine didn't know what eccentric loading was, and thought stretching is the best way to heal chronic tendonosis.
ReplyDeleteThe research is not well defined on the issue of "shin splints" even though you present it as such. The recent research only goes as far as "suggesting" that they are cause by "bone remodeling".
ReplyDeleteAs someone who treats runners on a regular basis, how do you explain when a runner with recurrent shin splints completely recovers after a couple of soft tissue treatments. This is a common occurrence in my office. Happens on a daily basis. One of my favorite injuries to treat because it responds so quickly.
Research is a means to an end, not an end in itself.
Hi Anonymous, thanks for the comment.
ReplyDeleteThe scientific evidence for bone remodeling is very convincing. CT scans, MRIs, bone scans, and bone mineral density tests all confirm that the bone tissue in the tibia is abnormal in runners with "shin splints" (more properly defined as medial tibial stress syndrome); additionally, theories pinning the problem on inflammation of the periosteum alone, or traction from muscles or tendons, don't hold up to scrutiny—histology studies of the periosteum don't consistently show inflammation, and anatomic studies show that the insertion points of the muscles in the lower leg don't line up with the most common location of medial tibial stress syndrome. However, finite-element modeling of the areas of the tibia bone under the greatest stress during running DOES correctly predict the most common location for medial tibial stress syndrome / shin splints.
It's great that you see success with your treatments, but don't forget that the vast majority of cases of shin splints recover spontaneously. I, too, work with runners on a daily basis as a coach, and this is something I see all the time without ANY real intervention. You could perhaps propose some methods by which soft tissue work could influence muscle function, which could influence biomechanics, which could influence the distribution of stresses in the lower leg, but to date there is no research on this.
For a review of the science behind the bone remodeling root of medial tibial stress syndrome, I recommend the following two papers and book chapter:
Beck, B. R. (1998). "Tibial Stress Injuires-An Aetiological Review for the Purposes of Guiding Management." Sports Medicine 26(4): 265-279.
Moen, M. H., J. L. Tol, et al. (2009). "Medial tibial stress syndrome: a critical review." Sports Medicine 39(7): 523-546.
Franklyn, M. and B. Oakes (2012). Tibial stress injuries: aetiology, classification, biomechanics and the failure of bone. An international perspective on topics in sports medicine and sports injury. K. R. Zaslav, Intech: 509-534.