Running with Medial Tibial Stress Syndrome - Part 1: What is causing my Shin pain?

By Brace Hayden, DPT and Miya Ensley

​Medial tibial stress syndrome (MTSS) has replaced the more alarming and antiquated term “Shin Splints” as the more helpful and broader regional pain diagnosis in the lower leg that can occur on either or both of the inner (medial) or the outer (anterior) part of the shin.  Many sore runners have joined the time-honored MTSS Club when they ramp up their mileage too quickly, or drastically alter their training routine (ie. by vigorously up-training plyometric exercises, track drills or increasing volume of hill workouts).

There are many working theories in sports medicine about what is going on when the tibia is stressed to the point of causing this painful and limiting condition. These theories include:

• Microtears and inflammation in the tibialis anterior muscle’s tendon (effectively a tendinitis) along its insertion to the shin/tibia (the muscle that helps lift and evert the foot, as well as decelerate the body during the running stride)
• An irritation of the tibia’s periosteum or a “periostitis” (the fibrous sheath that helps supply nutrition and blood to the bone, repair injured bone and contribute it’s to growth)  
• Combination of both uncomfortable theories

Differential Diagnosis of Medial Tibial Stress Syndrome: 
Pain in your lower leg doesn’t always fit the criteria for an MTSS diagnosis. There are two other similar unpleasant running ailments that can be confused as shin splints: 

• Compartment syndrome has a similar pain presentation along the outside of the shin, but typically has more swelling/pressure, nervy sensations and eventually progressive ankle weakness if untreated. Getting a proper medical diagnosis sooner than later is important, as compressed nerve injuries take a lot longer to heal. 
• Stress Fractures of the tibia can also present as shin pain when the repetitive impact of running causes partial fractures in the bone. These bone injuries can also be more sinister than shin splints, so getting a proper diagnosis from a medical provider (PT, MD, RN… not Dr. Google) is helpful and warranted. 
  • The typical pain of MTSS usually spans north and south along the tibia, whereas a stress fracture tends to be more point tender. 
  • Another differential point lies in their time of day presentation. MTSS tends to feel worse with the initial steps in the morning, as the muscles and connective tissue tighten up while resting. Stress fractures tend to feel better first thing in the morning as the bone has been unweighted throughout the night. 
  • Lastly, MTSS is typically more sore when you flex shin muscles, effectively lifting your toes toward your shin. Stress fractures conversely are usually not painful with resisted ankle flexion. 

Known Knowns That Can Contribute to Medial Tibial Stress Syndrome

• Too much, too fast: the aforementioned training error of increasing mileage or load too aggressively. 
• Hyperpronation: excessive rotation of the midtarsal (midfoot ankle bones) inward and downward, effectively collapsing the foot’s middle arch. Miles of running with 2.5-3x your body weight pounding through each over-pronated step could contribute to excess MTSS. 
• Sub-optimal pre/post-run stretching: stiff musculature in the lower leg can further stress on the connection area of the tibialis muscle on the tibia creating a higher potential for injuries.
• Worn-out shoes: this is not an exact science, as many people joyfully complete marathons barefoot. However, some aches and pains that accrue with higher mileage training can be improved with a new pair of supportive running shoes. 
• Imbalanced leg loading:  Uneven loading on one leg (ie. only running on the right side of a cambered road or only running around the track in one direction).
• Leg muscle strength deficits: an imbalance of pull between your calf muscles and the shin muscles can unevenly load, stress and cause running injuries.  See this prior RWM article on the importance of strength training your calves.

* Tune in next week for Part 2: Running with Medial Tibial Stress Syndrome - What do about Splintering Shins!