What causes mtss

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Last updated: April 4, 2026

Quick Answer: MTSS, or Medial Tibial Stress Syndrome, commonly known as shin splints, is primarily caused by overuse and repetitive stress on the shinbone and the connective tissues surrounding it. This often occurs during activities that involve running, jumping, or prolonged walking, especially with sudden increases in intensity or duration of exercise.

Key Facts

MTSS is a common injury among runners and military recruits, affecting an estimated 4-35% of runners.
It is characterized by pain along the inner edge of the shinbone (tibia).
Sudden increases in training volume or intensity are a major contributing factor.
Improper footwear or worn-out shoes can increase the risk of developing MTSS.
Biomechanical factors like flat feet or rigid arches can also play a role.

What is Medial Tibial Stress Syndrome (MTSS)?

Medial Tibial Stress Syndrome (MTSS), more commonly referred to as shin splints, is an inflammation of the muscles, tendons, and bone tissue around the tibia (the larger bone in the lower leg). It is a common condition, particularly among individuals who engage in high-impact activities such as running, jumping, and dancing. The hallmark symptom of MTSS is pain that occurs along the inner edge of the shinbone.

What Causes MTSS?

The primary cause of MTSS is overuse and repetitive stress placed upon the lower leg. When the muscles, tendons, and periosteum (the outer membrane of the bone) are subjected to excessive or repeated force, they become inflamed and irritated. This often happens when the demands placed on the lower leg exceed its capacity to adapt and recover.

Key Contributing Factors to MTSS:

1. Overuse and Sudden Increases in Activity:

One of the most frequent culprits behind MTSS is a rapid escalation in the intensity, duration, or frequency of physical activity. For instance, a runner who suddenly decides to increase their mileage by 50% in a week, or a new recruit in the military who isn't accustomed to long marches, is at a higher risk. The body needs time to adapt to new stresses, and insufficient adaptation time leads to microtrauma and inflammation.

2. Biomechanical Issues:

The way your body moves and is structured can significantly influence your susceptibility to MTSS. Certain biomechanical factors can place abnormal stress on the tibia and surrounding tissues:

Foot Mechanics: Conditions like overpronation (where the foot rolls inward excessively upon landing) or having excessively flat feet can cause the muscles in the lower leg to work harder to stabilize the foot and ankle. Conversely, a rigid, high arch can also be problematic, as it may not absorb shock effectively.
Leg Length Discrepancy: A noticeable difference in leg length can lead to uneven weight distribution and compensatory movements, increasing stress on the affected leg.
Muscle Imbalances: Weakness in the intrinsic foot muscles, calf muscles, or hip abductors can contribute to poor biomechanics and increased strain on the shin.

3. Inadequate Footwear:

The shoes you wear play a crucial role in shock absorption and support. Worn-out shoes that have lost their cushioning and support can no longer adequately protect the lower legs from the impact of activities like running. Wearing shoes that are not appropriate for the type of activity (e.g., using casual sneakers for intense running) can also be a contributing factor.

4. Environmental Factors:

Running on hard surfaces like concrete or asphalt can increase the impact forces transmitted to the lower legs compared to softer surfaces like grass or a track. Running on uneven terrain can also lead to awkward foot placements and increased stress.

5. Other Potential Factors:

While less common, other factors can contribute to MTSS, including:

Poor Conditioning: Lack of adequate strength and flexibility in the lower leg muscles.
Nutritional Deficiencies: While not a direct cause, deficiencies in certain nutrients like Vitamin D or calcium could potentially affect bone health and healing.
Hormonal Factors: In some female athletes, hormonal fluctuations have been suggested as a potential contributing factor, though more research is needed.

How MTSS Develops

The development of MTSS is typically a progressive process. It often begins with mild discomfort during or after exercise. If the activity causing the stress continues without adequate rest and recovery, the inflammation can worsen. This can lead to persistent pain even at rest, and in severe cases, can progress to stress fractures if left untreated.

Prevention and Management

Preventing MTSS involves addressing the underlying causes. This includes gradually increasing training loads, wearing appropriate and well-maintained footwear, incorporating stretching and strengthening exercises for the lower legs and feet, and considering the use of orthotics if biomechanical issues are present. If MTSS develops, rest, ice, compression, and elevation (RICE) are often recommended, along with modifying activity to less impactful alternatives until pain subsides.