That aches-a-lot feeling runners will recognize – a dull ache along the inside of the lower leg that begins soft but eventually becomes a pain that cannot be ignored. Medial tibial stress syndrome (or medial tibial stress reaction) is one of the most common overuse injuries in runners, representing about 10-15% of all running injuries. It affects the beginner racer logging their first few miles, marathon athlete hitting her high-volume training block, and everyone in between.
Here’s what is really going on in that tissue, and how that knowledge can help you make smarter decisions before you get hurt.
What Is Medial Tibial Stress Syndrome?
MTSS is pain running along the posteromedial edge of the tibia – or the inner lower part of the shin – due to excessive pain generating forces. The sensation is generally described as dull and achey and may be felt over a fairly large area (greater than five centimeters). This is in contrast to a tibial stress fracture, which is frequently very precisely localized to one specific point.
It occurs in response to repetitive mechanical loading that exceeds the bone’s ability to adapt, rather than through any acute traumatic event. It’s exactly that incremental progression which causes runners to ignore early signs of trouble.
Causes, Risk Factors, and Warning Signs
The top three causes of MTSS are: the volume increase is too rapid, hill work is added prematurely before you’re ready and running surfaces are too hard too soon. These are the three leading reasons why the tibia is overwhelmed for a period of time that it just can’t handle it. Those three conditions place stress on the tibia before it’s ready to accept the load.
Common biomechanical factors include overpronation, low arch structure and weakness around the hips. If shoe wear is old or doesn’t match your gait pattern, this can compound the effects. A previous history of a lower limb injury and sex have also been identified as risk factors in the clinical literature.
If the pain feels worse as a run progresses, it does not settle after your first mile and the pain lingers during the next day or two, it needs investigation. Sharp, localized pain, especially if it is associated with swelling, could be a stress fracture and that difference makes a critical difference.
Diagnosis and Evidence-Based Treatment
The clinician will evaluate the distribution and profile of symptoms and go over the history of training and examine gait mechanics. Although imaging may not always be indicated an MRI can help confirm the diagnosis of a MTSS case or exclude a stress fracture if the symptoms are unclear. Management of tibial stress syndrome focuses on relative rest (not pain-free rest, just lessen the intensity of the loading sufficiently to allow the tibia stress to diminish).
Avoid high-impact activities and focus on lower impact cross training modalities like aquatherapy or cycling, strengthening the calf complex, hip abductors and intrinsics of the foot. Increase running cadence very slightly as it will reduce tibial loads at runner.
Safe Return to Running and Prevention
A graded return is normally done pain-guided. If the pain is below three out of ten during running and recover within 24 hours of finishing, then it is usually considered safe to run again. Running mileage can be increased by no more than 10% per week; running on softer surfaces, getting adequate sleep and nutrition for bone, and replacing running shoes after every 400-500 miles all lower the risk of a repeat injury.
Doing strength training 2x/week (not just when injured) is probably the runners’ most under-utilized prevention tool.