Do I Have Shin Splints? Understanding Medial Tibial Stress Syndrome and Stress Fractures in Runners.
What are Shin Splints, Really?
“Shin splints” is a term tossed around a lot by runners, influencers, coaches, and even some physical therapists — often without a clear understanding of what it actually means. It’s kind of like saying you have “knee pain”: it tells you where it hurts but not why. That lack of clarity often leads runners down the wrong path: towards oversimplified rehab, prolonged recovery, re-injury, and frustration.
Shin splints is the layman’s term referring to pain along the inner edge of the shin bone (called your tibia), usually in the bottom two thirds towards the back side; however, it can happen anywhere along the tibia. The clinical name for this condition is Medial Tibial Stress Syndrome (MTSS). You will often read or hear that pain from shin splints is caused by overuse, inflammation, and weakness in the muscles or fascia around your shins. You might also hear it’s due to your high arches, overpronating, or your running form. All this leads to advice about orthotics, stretching, and strengthening your lower leg muscles to treat and prevent it. Unfortunately, all of this information is really not accurate or is only a small piece of the puzzle.
While MTSS is associated with overuse muscular weakness and pain, it is more accurately considered a type of bone stress injury, living along a spectrum that also includes stress fractures.
The Basics of Bone Anatomy and Remodeling
If MTSS is really a type of bone stress injury, what does that mean? To understand that it helps to understand a bit more about how bones work. Just like our muscles and tendons, bones adapt to training stresses that we place on them. Bones are constantly maintaining themselves, replacing old bone with new bone.
Bone is made up of two primary types:
Cortical bone: This is the hard, dense outer shell that provides most of the bone’s strength and protects the inner structures. It’s like the tough, protective bark on a tree.
Trabecular (or cancellous) bone: Found in the inner layers of bones, this type of bone is more spongy, porous, and honeycomb-like. It provides inner structure and allows blood and nutrients to flow to different parts of the bone. Bone marrow lives in the inner layers of some bones, which creates blood cells and stores fat.
MTSS occurs when our bone becomes overwhelmed by training and can’t keep up with its own maintenance. The biggest reason why it can’t keep up come down to energy availability.
Energy Availability and RED-S
What’s surprising to me is how little I hear clinicians talking about energy availability as it relates to MTSS, because it’s probably the most important contributor. Energy availability is the amount of energy your body has left over for body functions and repair after accounting for daily exercise and normal metabolism. In simple terms:
Energy availability = Energy in - Energy out
Low energy availability is when you take out more than you put in. When the balance tips into the negative, your body enters survival-mode and starts cutting back on non-essential functions: hormone production, menstrual cycles, immune function, bone remodeling, and more. Untreated low energy availability leads to Relative Energy Deficiency in Sport (RED-S), a more serious condition that affects athletes of any sex, weight, and experience level. RED-S will be covered in a future post, but it is a big problem in endurance runners and has a long recovery process. Low energy availability can happen intentionally, through undereating or disordered eating. Or it can happen unintentionally (more common), such as when you don’t adjust your intake during periods of high training load or stress.
As it relates to MTSS, a 2018 study found that just five days of low energy availability negatively impacted bone density, bone quality, and bone turnover — reinforcing how quickly under-fueling can contribute to this problem when paired with training patterns that stress the lower leg.
The Bone Stress Injury Spectrum
Bone stress injuries like MTSS don’t just appear suddenly. They are a progressive injury with different stages. When MTSS develops, imaging studies show signs of inflammation and edema (swelling) in the bone, starting in the outer layers (including muscle and tendon tissue) and progressing inwards. A neat study in 2022 showed how bone stress injuries in adolescents progress on imaging, giving us a helpful visual to look at.
Early Bone Stress
In this stage, the bone and surrounding tissue become irritated. In the image, you’ll notice the arrow pointing towards a slightly condensed, white patch by the shin bone. That is fluid and signifies stress in the outer layer of the bone and surrounding muscle/tendon.
What it Might Feel Like: You’ll get shin pain early during a run, but it will improve as you keep going. After the run, pain will go away or worsen. Daily activities typically feel normal.
What to Do: At the very least you need to monitor that symptoms don’t start becoming more regular during runs. Proactively, it would be smart to swap a weekly run for a bike for a couple of weeks. To protect the leg while running, keep away from speedwork and hills. If you’re also noticing signs of body fatigue, missed periods, or low sex-drive, you are likely under-fueling getting more calories in is a priority.
Bone Stress Injury
Now inflammation and swelling start to spread to the inner layers of bone marrow. On imaging, this appears as a brighter white area, but inside the bone. Again, this indicates fluid trapped inside the inner bone layers as a result of inflammation and more stress to the bone.
What it Might Feel Like: You’ll get shin pain during a run that either starts immediately or gets worse if you push through it. You’ll have pain that lingers after runs. Hopping on it may hurt. Walking might hurt, depending on the severity.
What to Do: If you feel like you’re dealing with symptoms like this, you should touch base with a physician or sports provider. These injuries are reversible, but most people likely need to take time away from running until they are non-symptomatic. When I dealt with one of these, I needed 4 weeks of strict no running to feel better - and I caught it early. That doesn’t mean you have to stop exercising. Many can still bike, lift, swim, and do yoga. It helps to work with a PT knowledgeable in these injuries so they can help you adjust your training plan and make sure your diet and recovery are optimized.
Stress Fracture
If stress continues untreated, the bone weakens enough to actually breaks. The black spot on the image shows the fracture. While the mechanism is different than falling and breaking your arm, these injuries are just as serious and take months to heal.
What it Might Feel Like: Most people who have one of these know something is wrong. You’ll get sharper pain even when walking, and you maybe have a limp. You keep weight off the leg. Running may not even be possible, and if you do try, pain forces you to stop.
What to Do: If you are worried you have one of these, see a provider who specializes in sports medicine. Don’t wait. These injuries need to be offloaded while the bone heals. Considering most of these injuries result from low energy availability, I’d really suggest seeing a sports dietician before you start training again.
What You Can Do to Reduce Your Chances of MTSS
As with all running-related injuries, prevention starts with early recognition and good habits, before you need to take time off training. Hopefully I’ve made the case that these injuries are more complex than strength and flexibility.
Here are some habits that matter:
EAT: Runners participate in a sport where it seems helpful to be lighter and leaner. If you’re going through a training cycle of high mileage or intensity, you need to eat more than you normally would, your body needs it! If you are unsure if you are taking in enough, connect with a knowledgeable provider to help you.
Don’t rush training: avoid big spikes in your mileage or intensity, especially if you’re new to running or returning after time off. Don’t just look at training week by week. Zoom out look at your broader training patterns. Some other general guidelines:
Don’t increase weekly volume by more than ~10% consistently.
Avoid letting your longest run of the week consistently exceed 50% of your total weekly mileage. For example, if you run 10 miles in a week, your longest shouldn’t be longer than about 5.
If adding speedwork, temporarily reduce your total mileage to offset for the new demand.
Lift weights: Resistance training has been shown to be a tried-and-true way to improve bone mineral density (with the caveat that you do it long enough and eat enough). You don’t have to lift weights twice a week year-round. Structure time in your year when you run less to focus in on it more.
Avoid chasing too many goals at once: For example, trying to increase running volume while also trying to improve strength gains in the gym will spread your recovery too thin. The body can only adapt to so much at once.
Respect warning signs and get help early: don’t ignore persistent shin pain, especially if it worsens after runs or creeps into your daily life. Pay attention to early signs of hormonal disruption such as persistent fatigue, frequent illness, or reduced sex drive.
Final Thoughts:
Many rehab plans for MTSS focus on surface-level fixes: strengthening the shin, stretching tight muscles, or correcting gait. While these can help in some cases, they miss the bigger picture, especially for runners dealing with MTSS or other bone stress injuries. In truth, injuries like MTSS arise from a mismatch between what your body is being asked to do and what it’s able to handle — and that balance is affected by much more than muscle strength.
Unfortunately, many rehab professionals don’t ask or are uncomfortable asking about things like diet, menstruation, libido, stress, or training history. They prescribe exercises without addressing the real reasons the injury happened in the first place. That’s why so many runners feel frustrated, stuck in cycles of recurring pain or never fully resolving the issue.
This post isn’t meant to scare you. Rather, to challenge the oversimplified advice out there, to help you ask better questions, and to take warning signs seriously. While a few runners might improve with basic fixes, true recovery often requires a multidisciplinary, individualized approach.
REFERENCES:
Brook EM, Tenforde AS, Broad EM, Matzkin EG, Yang HY, Collins JE, Blauwet CA. Low energy availability, menstrual dysfunction, and impaired bone health: A survey of elite para athletes. Scand J Med Sci Sports. 2019 May;29(5):678-685. doi: 10.1111/sms.13385. Epub 2019 Feb 6. PMID: 30644600.
Papageorgiou M, Dolan E, Elliott-Sale KJ, Sale C. Reduced energy availability: implications for bone health in physically active populations. Eur J Nutr. 2018 Apr;57(3):847-859. doi: 10.1007/s00394-017-1498-8. Epub 2017 Jul 18. PMID: 28721562; PMCID: PMC5861178.
Moen MH, Tol JL, Weir A, Steunebrink M, De Winter TC. Medial tibial stress syndrome: a critical review. Sports Med. 2009;39(7):523-46. doi: 10.2165/00007256-200939070-00002. PMID: 19530750.
Eric D. Nussbaum, Bryan Holtzman, Katherine H. Rizzone, Adam S. Tenforde, Mark E. Halstead, Corinna C. Franklin, Kathryn E. Ackerman. Evaluation and Diagnosis of Tibial Bone Stress Injuries in Adolescents: Imaging and Nomenclature. Journal of the Pediatric Orthopaedic Society of North America. 2022;4(1386):2768-2765. doi: https://doi.org/10.55275/JPOSNA-2022-0015.
Hong AR, Kim SW. Effects of Resistance Exercise on Bone Health. Endocrinol Metab (Seoul). 2018 Dec;33(4):435-444. doi: 10.3803/EnM.2018.33.4.435. PMID: 30513557; PMCID: PMC6279907.
Disclaimer:
This blog is for informational and educational purposes only and is not a substitute for medical advice, diagnosis, or treatment. Every runner is different, and what works for one person may not be appropriate for another. Always consult with a qualified healthcare provider before starting or changing your training or rehab program. If you're dealing with pain or injury, reach out to a licensed physical therapist or medical professional.
