Medial tibial stress syndrome is related to tibial stress reactions and stress fractures, which you can read about here
For an in-depth discussion of returning to running following a bone stress injury like medial tibial stress syndrome, see this article
Medial tibial stress syndrome (MTSS), or shin splints, is perhaps the best-known running injury to the average citizen. Aching or throbbing shins is an ailment that many new runners and many athletes in all sorts of impact-related sports, like volleyball, basketball, and sprinting, deal with on a regular basis. Unlike some running injuries, which appear to be non-discriminatory—both Joe Jogger and Ryan Hall suffer from plantar fasciitis, for example—medial tibial stress syndrome seems to be an issue encountered more often by new or seasonal athletes (though not exclusively). The reasons for this tie in closely with its root causes, which we’ll get to in a moment. Shin splints also have a complicated and fascinating relationship with tibial stress fractures, which we will also get to later on in the article. If you’ve read my Injury Series post on tibial stress fractures, you might see some familiar material. But first, as usual, we need a bit of anatomy.
Anatomy and terminology
The tibia is your “shinbone,” the long, straight bone that forms the front of your leg. The tibia carries a significant portion of the impact that goes up your leg when you hit the ground, and it also serves as an attachment point for the muscles that control your foot and ankle, all the way from the relatively small ones like the flexor digitorum longus muscle, which flexes your little toes, to the calf muscles, which are the engine below the knee for forward movement. The medial edge of the tibia runs up the inside of your leg and borders your calf muscles. The “stress” part of medial tibial stress syndrome just means that the condition is demonstrably associated with weight-bearing stress from exercise. And finally, as you may know from previous Injury Series articles, a “syndrome” is just any condition where the medical community doesn’t know or can’t agree on the cause. Other more exotic names for shin splints have cropped up, like “exercise-related lower leg pain,” but at this point, medial tibial stress syndrome or MTSS seems to be the predominant and most useful term. In this article, I’ll use these terms interchangeably with “shin splints,” the less-descriptive and colloquial term for this injury.
The most obvious symptom of MTSS is, of course, shin pain. The pain usually presents as an aching, burning, or throbbing feeling along the inside edge of the shinbone, usually dispersed over several inches along the shin. The shin (or often, both shins) gets progressively more painful throughout the duration of a run or workout. Early cases of shin splints might be nothing more than a bothersome ache near the end of a long run, but can progress to the point where even short jogs cause pain. There may also be some tenderness along the medial edge of the tibia. One review study recommends that medial tibial stress syndrome be defined as pain which extends for at least 2 inches along the middle to bottom-third of the shin, which is aggravated by weight-bearing and subsides with rest.1 Cases of shin pain which is localized to a very small area should be examined by a doctor to rule out a stress fracture. X-rays are insufficiently accurate to rule out a tibial stress fracture, so your doctor should use a bone scan or, preferably, an MRI, to diagnose your injury.
Mechanism of injury
Usually, this is where I’d jump into the nitty-gritty details about diagnosing MTSS and the risk factors for it, but it’s at precisely this point where the story begins to get interesting. Say an orthopedist sees two runners with shin pain. Both get a sharp pain in the medial tibia about a third of the way up, but the first patient has very localized pain over an area half an inch long that’s tender to the touch, while the second has much more diffuse pain that’s spread out over several inches. Most orthopedists would suspect that patient #1 has a stress fracture and would order an MRI or bone scan to confirm, while patient #2 would likely be diagnosed with MTSS and referred for physical therapy. But what’s the relationship between these injuries? Do they have different root causes? If patient #2 continues to train, could he or she develop a stress fracture? And are the causal factors the same?
Historically, medial tibial stress syndrome and tibial stress fractures were considered distinctly separate injuries. Stress fractures were suspected to be the result of impact forces traveling up the leg, while MTSS was blamed on tensile forces from the muscles of the lower leg “pulling” on their origin points along the tibia. The shin pain from shin splints was assumed to be due to inflammation or irritation of tissue surrounding the bone. Several authors conducted anatomic studies on cadavers and pointed to the flexor digitorum longus, soleus, or tibialis posterior muscles as the source of traction on the tibia. They all proposed that the tugging of the muscles at their origin points caused inflammation of the periosteum, a “skin” of tissue that surrounds the tibia.2, 3, 4
However, these studies could not agree on which muscles were responsible for the traction and subsequent periostitis (inflammation of the periosteum). Later anatomical studies and reviews concluded that the most frequent sites of pain from shin splints are too far down the leg to be a result of traction from any of the muscles that control the foot.4, 1
Additionally, studies which actually examined samples of the periosteum in athletes with shin splints did not find strong evidence for the traction/periostitis paradigm. In one study published in1982 by Johnell et al., researchers took samples of the tibia and periosteum from 20 athletes with shin splints, several with pain in both legs.5 Out of the 33 samples acquired of the periosteum, 13 showed inflammatory changes, but of the 35 bone samples, 22 showed some signs of increased metabolic activity. A similar study, published in 2000 by Bhatt et al., took 32 tissue samples of the tibia and periosteum from 20 athletes.6 Of these, 21 samples of the periosteum showed abnormal changes, but only a handful exhibited signs of inflammation. On the other hand, 16 of the 26 samples of tibial bone showed abnormal changes.
While sometimes helpful, studies which involve taking tissue samples have several problems associated with them. First, the tissue acquired is usually from athletes with very severe and long-lasting shin pain. Additionally, acquiring an adequate control group is quite difficult, since few healthy runners are keen on letting a group of doctors take a 3mm drill to their shinbone. Finally, because of the nature of tissue samples, they can easily miss what you might call a “heterogeneous” injury: one which isn’t evenly distributed across the injured area. As we’ll soon see, medial tibial stress syndrome is characterized by pockets of localized bone loss, which could have been easily missed by the drill bit. This might explain why a lot of the tissue samples in Bhatt et al. and Johnell et al. appeared completely normal, even in seriously injured athletes.
Fortunately, advances in medical imaging have allowed researchers to circumvent many of these limitations with high-resolution CT scans and MRIs. Scans of athletes with MTSS have revealed that the bone of the tibia is definitely involved in the injury process. In a landmark 1995 study, Fredericson et al. developed a grading system for MRI and bone scan results to categorize tibial stress injuries into medial tibial stress syndrome, tibial stress reactions, and tibial stress fractures.7 Mild forms of tibial stress injury are characterized by an abnormal signal for the periosteum, as well as a diffuse increase in bone synthesis in the tibia itself as seen on a bone scan. As the injury progresses, the bone marrow becomes involved and signals from the bone scan become more intense, and finally, in true stress fractures, a fracture line can be seen on the MRI. This is beautifully illustrated in the MR images to the left, taken in a 19-year-old female volleyball player who continued to train with shin splints. The MRI clearly reveals the worsening of her condition after a week. Fortunately, the authors report that this subject recovered with rest in under a month. Additionally, the grading system of Fredericson et al. allows an estimate of how long it will take for the athlete to return to running.
Further work with CT scans has confirmed a definite role of bone injury in shin splints. Michele Gaeta and colleagues at the University of Messina in Italy have published two fantastic studies on using MRI and CT scans to image the bone resorption process in both healthy training and medial tibial stress syndrome.8, 9 The series of cross-sectional CT scans of tibias below clearly demonstrates that the tibial cortex, the hard shell of the bone that gives it its strength, display abnormalities in athletes with shin splints.
|CT tibial cross sections of A) a healthy runner B) a healthy runner showing normal signs of bone resorption/growth (dots) C) a runner with medial tibial stress syndrome and marked areas of low bone density and resorption (arrows) D) a runner with MTSS and a larger area of osteopenia/low bone density and bone resorption associated with overloading of the tibia (arrows and arrowheads). Adapted from Gaeta et al. and Gaeta et al.|
However, the work of Fredericson et al. and Gaeta et al. have also highlighted an important fact that’s key to understanding the mechanism of injury in shin splints: many healthy athletes display mild abnormalities of the periosteum and the tibial cortex in MRI and CT scans! Herein lies the key to understanding the link between medial tibial stress syndrome, stress reactions, and true stress fractures. All three are a result of excessive loading on the tibia. This finding is bolstered by bone density studies which have shown that athletes with medial tibial stress syndrome have lower bone density in the tibia10 which seems to increase once they have recovered.11 Moen et al. succinctly summarize the findings as follows:1
There are four important findings that support the theory that bony overload forms the primary pathophysiological basis for MTSS: (i) on triple-phase bone scans the last phase is abnormal, showing that the bone and periosteum are involved (ii) on high-resolution CT scan the tibial cortex is found to be osteopenic, as can be seen in patients as well as in asymptomatic athletes as a sign of bone remodelling (iii) on MRI images, bone marrow oedema as well as a signal along the periosteum can be seen (iv) in patients with MTSS, bone mineral density is reduced compared with controls, and when symptoms improve, the bone density returns to normal values.
Bone loading and remodeling
One fundamental property of biological tissues in the human body is that they respond to stress; bone is no different. When it’s subjected to stress, from running, jumping, or any other weight bearing activity, your tibia initiates a remodeling process through which it becomes stronger. This is why impact activities promote a high bone density, and are encouraged as a method of preventing osteoporosis. However, remodeling a bone is a rather lengthy process—it can take a month or two for your bone to adapt to a new stress, and during that window of time, your tibia can actually be weaker because of the way remodeling occurs.12 Just like remodeling your kitchen might entail tearing out some walls before you can put in new construction, your body has to resorb areas of bone tissue in the tibia before it can strengthen it. This explains why bone resportion cavities are seen in healthy runners, as their body is adapting to the stress of training as it should.
But what causes the progressive weakening of bone in MTSS? The most likely explanation is that the stresses of training outpace the body’s ability to remodel the bone, so the problem becomes a compounding one: additional stress induces bone resorption in the tibia, which leaves the bone more vulnerable to additional stress. Research to date indicates that tibial stress is not so much from compressive forces going straight down the tibia but from bending forces that cause small deflections in the bone.13, 14 However, a number of factors have been associated with medial tibial stress syndrome; first, we’ll review them, then we will examine how they might contribute to excessive tibial loading and what can be done about it.
|According to Popp et al. and Bennell et al., damage to the tibia occurs due to bending in the sagittal plane.|
Epidemiology—who gets it and why
Shin splints are a fairly common running injury. They account for 4-5% of all running injuries,15, 16 and 12-15% of high school cross country runners will suffer from MTSS at some point during a season.17, 18 Women are roughly twice as likely to get it as men. As you might expect, many of the causal factors are related to underlying bone structure.
One exceptionally thorough 2008 study out of Monash University in Australia demonstrated that tibial geometry in both men and women are strongly linked to the development of both tibial stress fractures and medial tibial stress syndrome.19 Franklyn et al. used high-resolution CT scans to analyze the cross-sectional geometry of four groups of people: athletes with tibial stress fractures, athletes with medial tibial stress syndrome, healthy athletes, and healthy sedentary people. Men and women were split into subgroups within each category. Using a mechanical engineering approach, Franklyn et al. used computational analysis to calculate a variety of mechanical properties of the tibias of the various subjects, many of them related to how well the tibia resists bending forces. Their findings were quite impressive:
- In men with tibial stress fractures or MTSS, the tibia was ill-equipped to resist bending forces as a result of a smaller cross-sectional area compared to the healthy athletes
- In women with tibial stress fractures or MTSS, the tibia was also less resistant to bending, but because of the way in which the bone was distributed about the central axis of the tibia. The leading edge of the tibia was further away from the center of the bone, which would lead to increased strain during backwards bending.
- In all groups, the bone geometry of the injured athletes and the sedentary controls was similar, but significant differences existed when comparing these groups to the healthy athletes.
- Bone geometry differences that predicted stress fractures also predicted medial tibial stress syndrome
This last point in particular adds further evidence, in my opinion, to the idea that medial tibial stress syndrome and tibial stress fractures exist on a continuum of tibial bone injuries. I should note, however, that Franklyn believes that they are related but different injuries.20 Her reasoning is that not all cases of MTSS lead to stress fractures, and that MTSS is a diffuse injury, while stress fractures are localized. I believe that both of these can be explained by variations in bone remodeling rates.
Franklyn et al. also acknowledged that it’s likely that bone density plays a role in the development of tibial stress injuries in women, though they did not measure it in their study. Indeed, we know from other studies that bone density is related to stress fractures in women, but not men. The menstrual cycle plays a key role here, as disturbances in menstruation brought about by inadequate nutrient intake and disordered eating lead to hormonal imbalances and a reduction in bone density, a condition known as the female athlete triad. Studies on stress fractures in women have found that missing more than one or two menstrual cycles a year leads to a substantial increase in stress fractures and a drop in bone density.21 Differences in bone density may explain why women suffer disproportionately from shin splints.
Some studies (but not all)22 have also connected calf size and strength with medial tibial stress syndrome.23 In theory, larger and stronger calf muscles encourage the tibia to become stronger and thicker, a phenomenon observed in some studies of women at risk for tibial stress fractures.13 In addition to promoting stronger bones, the calf muscles also absorb impact forces directly.24 A weakened calf musculature would require the tibia to take more of the pounding during impact. Indeed, a 2007 study found that athletes of both genders who have medial tibial stress syndrome have demonstrably weaker calf muscles, as measured by a single-leg calf raise test.25
While early work linked foot pronation with MTSS, especially in recreational sports participants and military recruits, more modern studies in runners have been less clear. Two very similar prospective studies on large groups of high school cross country runners found conflicting results: Bennett et al. found that navicular drop, a proxy measurement for foot pronation, was a strong predictor of shin splints among high school runners,17 but a later study by Plisky et al. found no relationship between the two, and cited three other large studies on runners which also found no relation between pronation and MTSS.18 Bennett et al. fired back again in July of this year with a larger prospective study of collegiate cross country runners which found that runners who pronate while standing are more likely to get MTSS; additionally, they found no link between calf endurance and the propensity to develop shin pain.22 Interestingly, Bennett et al. propose that the link between calf endurance and shin splints found in some studies may simply be a proxy for overall fitness: presumably, a fitter athlete would have strong calves, and also be less prone to MTSS, though perhaps not entirely because of his or her calf strength. It’s well established that poor physical fitness is a predisposing factor to MTSS in military recruits, and I suspect the same relationship would hold for runners—less-fit runners would presumably have been training less or not at all, and hence would not have the tibial bone strength of a runner training full-time.
If pronation is a factor, it’s likely because pronation of the foot shifts the ground reaction force toward the inside of the leg, putting additional pressure on the medial edge of the tibia. While the prevailing opinion among biomechanics researchers appears to be that the main cause of tibial stress is bending in the sagittal plane (a “backwards” bending of the tibia), prominent podiatrist Kevin Kirby argues that increased pronation leads to bending in the frontal plane (a “sideways” bending of the tibia), which he believes can be treated with custom foot orthotics.26 His logic is that a medial wedge, an outward slant in an orthotic underneath the inside of the foot, will shift forces laterally, taking strain off the medial tibia. While it’s an interesting proposition, and explains why some runners find relief from MTSS in custom orthotics much better than the old “pronation control” paradigm, any experimental evidence for this idea is still lacking.
Finally, given the strong link we’ve established between shin splints and more serious tibial injuries (stress reactions and fractures), it is reasonable to suspect that a high impact loading rate is connected with MTSS, since it’s been implicated in tibial stress fractures.27 Franklyn et al. argue that tibial bending is not caused by the impact forces, but the active forces which follow, during the “push off” phase of gait.20 Both opinions may well be right: let’s not forget that impact forces and active forces are intimately related when we consider stride frequency. Taking an extreme case, bounding for distance is a “running gait” with a very low cadence, very high impact forces, and very high active forces. At the other end of the spectrum, running at a slow speed with a high cadence is a gait with low impact forces and low active forces as well.
|It's uncertain whether the impact peak (left) or the active peak (right) of the overall ground reaction force is to blame for medial tibial stress syndrome. Both may be involved. Fortunately, strategies to reduce one tend to reduce the other.|
Franklyn also describes a highly detailed computer model that demonstrated that overloading on the tibia appears to be the result of high tensile stress (due to bending forces) on the external surface of the medial side of the tibia, and additionally, that this stress peaks during the active part of the gait cycle. When looking to prevent or treat MTSS, we’ll have to look for strategies which can decrease the bending from the active force peak (and/or the impact peak), or at least strengthen the bone’s resistance to it.
|Computer model which predicts that the maximum stress on the tibia is a result of bending forces encountered during the "push off" phase of gait. From Franklyn and Oakes.20|
Prevention and treatment
Happily, most cases of medial tibial stress syndrome are mild and resolve quickly. In the Plinsky study on high school cross country runners, the majority of cases resolved with only 1-4 days of missed training. It’s reasonable to suspect that the root cause of MTSS in most cases is simple overloading of the tibial bone. Jumping from a relatively sedentary lifestyle into a high volume of running (or any other impact activity for that matter) can load the tibia with more force than it can handle. The tibia will eventually adapt to the new load, but bone remodeling appears to be a fairly slow process. And, problematically, there is a window of time during the remodeling process where the tibia is actually more vulnerable to stress.
Despite its prevalence in athletes and military recruits, there have been very few studies of treatments for MTSS, especially in runners. No solid treatment or prevention protocol has been identified, so as with tibial stress fractures, we will have to do some deductive reasoning using what we know about the causal factors to predict what might prevent or treat shin splints. To this end, treatment and prevention protocols should be oriented on reducing the stress on the shin and improving the strength of the tibia.
Reducing tibial stress
Decreasing the shock that goes up the shin should reduce symptoms and give the body a better shot at strengthening the tibia even as training continues. From a biomechanical perspective, two surefire ways to reduce tibial stress from impact and from active force peaks are by increasing your stride frequency by 10% or so and by slowing down the pace on your runs. Many runners have a tendency to drop their stride frequency when they slow down, so you’ll have to check your cadence regularly to make sure you’re not getting lazy with your running form. While there’s nothing magical about a stride frequency of 180 steps per minute, most elite runners (and, in my observation, most injury-resistant runners) have a cadence of at least 180, even at slow paces, and it’s very difficult to overstride at stride frequencies of 180 or above. The best way to check your stride frequency is to count the number of times your right leg hits the ground while running for 30 seconds, then multiply by four. Ideally, you’d count 45 or more right-foot strikes in 30sec. If your cadence is lower than this, moving right up to 45 will feel unnatural, so you’ll have to spend some time to work your way up. Check often, and if you can, try running behind a friend who has a stride frequency of 44-45 and matching his or her cadence. Slowing down the pace on your runs is just a matter of self-control. It seems like this is a problem for young, highly talented runners, since they can maintain a very fast training pace on account of their raw fitness but have not yet allowed their bones to adapt to the stresses of training. If this sounds like you, try backing off your training pace by 30 or even 60 seconds per mile. Remember that there’s good evidence that the harder you push off from the ground, the higher the stress on your tibia. Plenty of extremely fit runners trot along at 7 or 8-minute miles in training!
Decreasing your training volume or intensity is another obvious way to reduce stress on your tibia, but is probably the least palatable treatment to the serious runner. While you’re virtually certain to recover with a few weeks’ rest, this is a non-starter for any in-season athlete. A better approach might be to cut out any unnecessary mileage: shorten warm-ups and cool-downs, lower the distance of your easy days, and don’t push too hard when working out. Figuring out how to calm down MTSS while still continuing to train and race is a difficult and highly individual challenge, so I can’t offer any more broad advice on that front. Do keep in mind that MTSS and tibial stress fractures likely exist on a spectrum of tibial stress injuries, so foolishly pressing ahead with shin pain could land you in a boot for a month or more.
Many runners and coaches think that running on a softer surface like dirt or grass will reduce tibial loading vs. running on concrete or pavement, but that isn’t borne out by the research. In fact, some theoretical work suggests that tibial shock might be higher on softer surfaces. This is because of the way your body adapts to running on surfaces of varying stiffnesses.28 In order to maintain a consistent path for your center of gravity, your body adjusts the stiffness of your legs based on the surface you’re running on. So, when you run on a hard surface in thin shoes, your legs become more compliant, and in contrast, in thick shoes on a soft surface, your legs become stiffer. Having high leg stiffness is one factor that’s been connected with tibial stress fractures29—a few researchers hypothesize that running with a high leg stiffness stresses the “firm” tissues of the leg (the bones and the joints), while a low leg stiffness stresses the soft tissues (the muscles and tendons). This leg stiffness approach may explain why some runners have found that barefoot running or minimalist shoes have allowed them to overcome MTSS when custom orthotics, pronation control shoes, and icing failed: the high stiffness of the ground and shoe (if any) forced their legs to become much more compliant, transferring stress from the tibia to the calf and shin muscles. If you are feeling particularly adventurous and want to try out an untested treatment protocol, or if you are at your wit’s end after having been failed by other more cautious treatment methods, you might consider switching to running in thinner, firmer shoes on a harder surface. Needless to say, this is a rather drastic step, so this really ought to be a last resort. Additionally, I recommend avoiding wearing extremely thin shoes like the Vibram FiveFingers on very hard surfaces like asphalt and concrete, as some worrisome reports suggest this might increase your risk of metatarsal stress injuries.30
However, this entire paradigm rests on the central nervous system working properly in injured runners. As pointed out by podiatrist Ian Griffiths on Podiatry Arena, it’s possible that injured runners might have a leg stiffness that’s “stuck” at a high level. In this case, running on hard surfaces would be more injurious, as it would lead to a mismatch between the surface and the leg stiffness. If this were the case, runners with shin splints should stick to softer surfaces until their central nervous system “resets.” My intuition tells me that the CNS still works properly in injured runners, but things are often not as they seem in this sport! Check out this post for some more thoughts on this concept.
Despite all of this blustering about theory, many runners still find that soft surfaces are kinder to their shins. Why is this? It could be just a perception bias, but I suspect that surface irregularity plays a role too. Soft, natural surfaces, like gravel roads, dirt trails, and grassy fields, tend to be much more irregular than a concrete sidewalk or asphalt road. This might mean that each step stresses your foot and leg slightly differently, distributing stress across more areas of tissue and perhaps sparing your shins.
Another reason why runners sometimes find their shin issues resolving when they begin to run in minimal or no shoes is the resultant change in running form. It’s well-documented that running barefoot results in a flatter foot placement, and forefoot or midfoot striking is much more prevalent in habitual barefoot runners than in the athletic population at large.31 While a forefoot or midfoot strike (or even a flatter heelstrike) has not been proven to be any “better” than normal heelstriking, theory does indicate that these footstrike styles do transfer loads from the shin and knee to the foot, ankle, and calf muscles. In the case of medial tibial stress syndrome, this could also result in lower impact loads on the tibia. However, you’re introducing new stresses on the metatarsals, Achilles tendon, and calf muscles, and a drastic alteration in running form is a very high-risk endeavor for anyone but a complete novice.
On the other hand, some runners have also found that custom orthotics allow them to overcome MTSS. Two studies of military recruits did find that custom orthotics can prevent shin splints,1 but to date no studies have investigated the benefits of orthotics in a non-military setting. If custom orthotics do have any benefit in preventing or treating MTSS in runners, the mechanism is likely best explained (for now) by either Kevin Kirby’s hypothesis that supporting the medial side of the foot brings the ground reaction force more in line with the tibia, reducing bending in the frontal plane26 or by Benno Nigg's hypothesis, that insoles which encourage your body's "preferred path of motion" reduce tissue stress. While Kirby's theory has no experimental backing and Nigg's only has a few experimental studies to its name, it may be worth trying a pair of PowerStep or SuperFeet insoles in your shoes, as this will only cost you about $40. Custom orthotics are significantly more expensive, but may be worth trying if you are having long-standing shin pain.
A less risky option to unload the tibia is to strengthen the calf muscles. As proposed by Madeley et al.,25 runners with MTSS may have poor calf endurance compared with healthy controls, and in women, smaller calf muscles have been linked with a smaller and weaker tibia.13 Unfortunately, there’s no agreement yet on what constitutes a “good” calf strengthening regimen. Single-leg calf raises are a good place to start. Looking back at successful strength exercise routines for other injuries, it’s likely that a successful program would involve multiple sets of single-leg calf raises, perhaps several times a day. A hypothetical program might start with 3x15 single leg calf raises (on both sides) twice a day, progressing towards 3x30.
Some coaches and athletic trainers have also found success in strengthening the other muscles of the lower leg that control the foot and ankle. While the calf muscles absorb the bulk of the impact traveling up the leg, it’s probable that the smaller muscles play a role too. Russ Ebbets, a chiropractor and lecturer on track and field, developed a six-part “foot drill” routine that’s been used by various sports programs with the goal of reducing foot and lower leg injury. While there’s no scientific evidence for its efficacy, I’d be remiss to leave this routine out. Franklyn et al. also mention that some studies have connected weak foot inverter muscles with MTSS, and that perhaps some of the excessive pronation in runners with MTSS is due to “dynamic” pronation (because of weak foot inverter muscles), giving credence to the “inside up” exercise in Ebbets’ foot drill routine.20 The foot drill routine, presented below, should be done every day for about 10-20m for each drill. Ideally, the drills are all done barefoot on a soft surface.
|Russ Ebbet's six foot drills. They should be done for 10-20m each, without shoes on a soft surface if possible.|
Improving tibial strength
Despite all of the above treatments, to fully recover, you need to allow your tibia to become stronger. By far the most important factor in doing so is TIME—current literature indicates that the bone remodeling process takes several months to fully complete. The window in which bone resportion makes the tibia more vulnerable to stress is around 30-45 days after the initial increase in stress, at least according to a paper by Belinda Beck at Stanford University.12 This corresponds well to studies of military recruits, which find that incidence of stress fractures peak within the first month of basic training. I cannot stress enough that an intelligent, gradual training program is the best way to increase tibial bone strength. Runners, when healthy, have significantly higher bone density than sedentary people, and the benefits of this extend well beyond resistance to stress fractures. The considerations below are important, especially for runners with chronic cases of MTSS, but for most runners, gradual progression of training is the ideal way to build up bone strength. Interestingly, the kinetics of bone remodeling suggest that perhaps the best way to progress with your mileage if you are prone to shin splints is not a simple 10%-every-week model.
Taking periodic “down weeks” every three or four weeks will give your shins a break from the continual strain of training. So, your mileage progression might look like this:
Another option is what you might call an “equilibrium” approach, as advocated by Jack Daniels. In this method, you increase your mileage by a larger amount but take several weeks to adapt to the new volume. In this case, your mileage progression might look like this:
Sometimes, despite following an intelligent training progression, runners still find themselves beset by shin problems. In this case, it’s time to think about what else could be affecting the strength of your tibia.
For women, these concerns revolve mostly around nutritional and hormonal well-being. Too many female runners miss their menstrual period (amenorrhea) due to inadequate caloric intake and disordered eating, a condition known as the female athlete triad. While the details of this are complicated, the end result is undesirable changes in hormone levels, which ultimately lead to a loss of bone density and an increased risk of tibial stress injury.21 It’s worth repeating that female athletes missing their period on a regular basis is a very serious issue whose consequences are far greater than simply being at an increased risk for shin splints. If you exhibit signs of disordered eating, including fatigue, weight loss/a low BMI, a preoccupation with food/weight, and amenorrhea, seek help from your coach and family doctor.
On the preventative front, one study of female navy recruits also found that taking a calcium and vitamin D supplement every day, totaling 200% of the RDV of both, decreased the risk of a stress fracture by 25%.32 Given the link between lowered local bone density and MTSS, it’s possible that such a regimen would also decrease the risk of medial tibial stress syndrome. Men may also benefit from calcium/vitamin D supplementation, though this too is unproven.
Finally, it’s worth rehashing that calf strength and size may be linked to tibial strength. In one paper, Popp et al. link bone size with muscular cross-sectional area—that is, the smaller your calf muscles, the weaker your tibia. This may be because the tibia responds to the maximum forces it encounters, and these occur not during impact, but during active force production (when you push off the ground). If you have weak calf muscles, your tibia will not encounter a large stimulus to become stronger. However, if the mechanism of injury is impact (not active forces), you have a recipe for trouble. This theoretical link may not be accurate, but at the end of the day we still have solid experimental proof linking small calf muscles to slender tibias. Additionally, even if calf strength per se is not linked to MTSS, doing lower leg strengthening exercises with weights is a great way to strengthen the tibia anyhow, as one 2009 study demonstrated that weight training increased tibial bending resistance in young women.36 Squats, lunges, and calf raises all strengthen the lower leg muscles, but perhaps more importantly, also progressively load the tibia, encouraging it to become thicker and stronger. The specifics of an “ideal” weight program for runners are well beyond the scope of this article, and not really my area of expertise anyhow, so I’ll let you do the legwork on that. Road to the Top by Joe Vigil and Better Training for Distance Runners by David Martin and Peter Coe both have chapters on weight and strength training.
Directions for future research
When doing literature research for this article, I was surprised at the lack of scientific enthusiasm for studies on treating and preventing medial tibial stress syndrome. With most other Injury Series articles, I was able to identify several studies of various treatment protocols, even though many of them were not effective. In the case of MTSS, there are very few studies on treating and preventing it, and among those that do exist, almost all are on military recruits. While military studies can be helpful, there are obvious differences between marching with a weighted pack for several miles a day on little sleep and the normal training of a recreational or competitive runner. As we saw with foot pronation, some factors which are clearly linked to the development of shin splints in military populations are much more controversial in runners.
One interesting area of research is extracorporeal shockwave therapy or ESWT. While ESWT has been pursued more vigorously as a possible treatment for connective tissue problems like plantar fasciitis, one study from July of this year found that it significantly improved recovery time from MTSS.33 While this study was reasonably large (42 athletes, all of which had been suffering from shin splints for at least three weeks), more research needs to be done on shockwave therapy as a treatment for chronic medial tibial stress syndrome.
Calf strength is another area that needs to be vigorously pursued as a possible prevention and treatment program. I suspect a successful calf strength program will be fairly rigorous, i.e. not just a dozen half-hearted calf raises every day, but several sets of single-leg raises multiple times a day to rapidly improve strength and endurance. Popp et al. have proposed that tension from the calf muscles can prevent tibial bending, much like a cable-stayed bridge is held rigid by tension in its supporting wires.13
|Future research should investigate whether calf strength can reduce tibial bending|
I would also like to see some research on the use of medially-wedged orthotics as a possible treatment for MTSS. As I tend to believe Benno Nigg’s34 theories on the function of orthotics in runners, I personally doubt there would be a significant effect in all runners, but it is well worth the investment of a few studies to lay the issue to rest—I’m sure plenty of highly qualified people disagree with my opinion on this.
Lastly, more work should be done on using engineering principles to predict who is likely to suffer a tibial stress injury. The work of Franklyn et al. is very important because it demonstrates the usefulness of an engineer’s approach to biomechanics: when they treated the tibia like a structural beam supporting a building, they were able to determine what factors were at play in men and women who suffered from MTSS and tibial stress fractures. I hope we see more studies of this nature in the future, perhaps applying the same principles to other stress fracture-prone areas like the metatarsals, the navicular, and the femur.
First off, if you are suffering from shin splints, don’t panic! The vast majority of cases are mild and recovery quickly. Understand that the root cause is overloading of your tibia, likely brought about in most runners by a rapid increase in training volume or intensity. Second, don’t train through it with reckless abandon! Because medial tibial stress syndrome is an injury to the bone, you may risk developing a stress fracture if you continue to train and race with shin pain. Many runners find that icing their shins is a helpful way to reducing pain, but don’t forget that to fully recover, you need to decrease stress on your tibia and strengthen the bone itself.
Depending on the severity of your injury, you may need to take a few days or even weeks off to fully recover—remember, your bones are actually weaker for the first month following a significant increase in training. If you do continue to train, reduce the volume, intensity, and frequency of your runs if you can. Work with your coach to weigh the risks and benefits, keeping in mind your short-term and long-term goals. Additionally, work to decrease your impact loading rate by upping your stride frequency by 10% or so, bringing it closer to (or above) 180 steps per minute. You might also try varying the surfaces you run on to see if a hard, even surface or an uneven natural one is friendlier to your shins.
Both to take stress off the tibia and to encourage it to grow thicker, you should strengthen your calves and the smaller muscles of the lower leg. While there’s no proven protocol for either of these yet, doing single-leg calf raises (starting with perhaps 3x15 and progressing to 3x30) and Russ Ebbett’s foot drill routine every day are a good place to start. Supplementing your normal training with some light barefoot running on grass every week may also strengthen your lower leg muscles, and the flatter and more forward landing style you’ll inevitably adopt during these barefoot sessions may load your shins less than when running in shoes. Additionally, introducing lower-body weight training could strengthen the bones and muscles of your lower leg, increasing their ability to handle the stresses of training.
In the future, consider adopting a training progression which allows some time for your bone to heal, such as taking a “down week” every 3-4 weeks or adopting Jack Daniels’ “equilibrium” model with periodic mileage increases separated by several weeks of even volume.
If your shin pain localizes to an area under about two inches in size, aches even when you aren’t putting weight on it, or keeps getting progressively worse, you should cease training and see an orthopedist to check for a stress fracture. While a bone scan is sufficient to accurately diagnose stress fractures, an MRI is the preferred imaging tool because it can give a more precise reading on the severity of the injury and perhaps even provide you with an estimate as to how much time it will take to recover.
A small minority of runners suffer from shin splints on a chronic basis, even with careful monitoring of their training and recovery. If this is the case, you should consider more aggressive treatments in addition to increasing your cadence and strengthening the muscles of your lower leg. Over-the-counter orthotics, like SuperFeet Green or PowerStep, are a good place to start, and some distance runners (and other athletes with shin issues, like long jumpers, hurdlers, and sprinters) find that these can help. True custom orthotics from a good podiatrist are a logical extension of this, and have been shown to help prevent shin splints in military recruits. Supplementing your diet with 200% of your RDV of calcium and vitamin D is also a relatively low-risk approach that may help with underlying bone issues, especially in women. Female runners with chronic shin issues should examine their dietary habits and review their menstrual health. The various factors of the female athlete triad can lead to a whole host of problems beyond medial tibial stress syndrome.
Finally, there are some riskier strategies that, while being theoretically sound from our current understanding of biomechanics, are experimentally untested or carry some risk of additional injury. Running in firm, thin shoes on a hard surface like asphalt or concrete should (in theory!) reduce stress on the tibia because your overall leg stiffness should drop, transferring stress to the soft tissues of your leg. Unfortunately, there’s the very real risk of increasing the stress on your metatarsals with this approach,35 so do be conscious of this.
Running in minimal shoes (or none at all) is also likely to promote more of a forefoot/midfoot striking style, which is something you could actively work to develop if so desired. Like the firm shoes/hard surfaces theory, changing your footstrike style should in theory reduce impact loading on your tibia, but you run a significant risk of injury to the metatarsals, Achilles tendon, and calf muscles while your body adapts to the switch.
Lastly, depending on the medical practitioners in your area, you may be able to find a doctor willing to try a multi-week course of extracorporeal shockwave therapy if you’ve had long-standing shin problems. While there aren’t as many risks with this treatment, I’m hesitant to recommend it based off of just one study, especially considering that ESWT is a new and relatively unproven treatment in general.
In all, treatment and prevention of medial tibial stress syndrome needs to take into account that it is a bone injury, not simply an inflammation of soft tissue at the inner edge of the medial tibia. Therapies, both current and future, should be directed at reducing strain on the shin and increasing the strength and resilience of the tibia itself. I hope that future research brings us closer to having a solid exercise or therapy program that can successfully treat or prevent shin splints.
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