Bone Stress Injuries in Runners: Why They Develop Gradually (And How to Spot Them Early)

Bone stress injuries are one of the most common overuse injuries we see in runners.

They are also one of the easiest injuries to miss early because symptoms often develop gradually.

Many runners assume a stress fracture happens suddenly — from one hard run, one race, or one training session.

The reality is very different.

Bone stress injuries usually develop over time when the demands placed on the skeleton exceed the body’s ability to adapt and recover.

Understanding this process is key to recognising early warning signs and preventing a manageable problem from becoming a significant setback.

A Sports Medicine Perspective

Recently, our clinical team spent time with sports physician Dr Mark Fulcher from AXIS Sports Medicine discussing bone stress injuries, how they develop, and how clinicians can identify athletes at risk earlier.

A key message from the session was that bone stress injuries should be viewed as a progressive overload condition rather than a single injury event.

In practice, the most important question is often not:

"What caused the pain today?"

but:

"What changed in the weeks leading up to this?"

This could include:

• An increase in running volume

• More intense sessions

• Returning too quickly after injury

• Adding races or competitions

• Changing footwear or surfaces

• Adding strength training without reducing another training demand

Your Bones Are Constantly Adapting

One of the biggest misconceptions is that bone is a fixed structure.

Bone is living tissue that constantly responds to the demands placed upon it.

Every run creates tiny amounts of stress within the skeleton.

This is completely normal and is actually part of how bone becomes stronger.

The body removes older bone tissue and replaces it with new, stronger bone.

The challenge is that this process takes time.

Bone remodelling occurs over several weeks, meaning the body needs enough recovery time between increases in load.

When training demands increase faster than the body can adapt, microscopic damage can accumulate and a bone stress injury can develop.

Why Bone Stress Injuries Often Appear Weeks Later

One of the confusing things for runners is that symptoms often do not appear immediately after a training change.

A runner might say:

"I only increased my mileage two weeks ago — why is my shin hurting now?"

The answer is that bone adaptation is delayed.

The training change that contributed to the injury may have happened several weeks earlier.

This is why bone stress injuries are common during:

• Marathon preparation

• Winter training increases

• Pre-season sport preparation

• Return to running after injury

• Periods of increased competition

Why Do Bone Stress Injuries Happen?

A bone stress injury develops when there is a mismatch between:

The load placed on the bone

and

The ability of the bone to tolerate that load

Sometimes this is due to excessive training load.

Examples include:

• Increasing mileage too quickly

• Adding hills or speed work

• Increasing race frequency

• Returning too aggressively after time off

However, it is not always about running more.

Other changes that increase bone stress include:

• Adding gym training while maintaining the same running volume

• Changing running surfaces

• Changing footwear

• Increasing intensity while keeping volume high

A useful way to think about training load:

If you add another stressor, something else may need to temporarily reduce to allow your body to adapt.

The Warning Signs We Look For

Bone stress injuries often behave differently from muscle or tendon problems.

Common warning signs include:

Very specific pain

Many runners can point directly to the painful area with one finger.

This localised pain is different from normal muscle soreness.

Pain that does not warm up

Some muscular symptoms improve once you get moving.

Bone stress injuries often do not.

Pain that becomes easier to trigger

Early symptoms may only appear after longer runs.

Over time, pain may occur earlier and last longer afterwards.

Other warning signs include:

• Pain with hopping

• Pain after exercise

• Pain while walking

• Night pain

If you are repeatedly pointing to the same small area, it is worth getting assessed.

Who Is More At Risk?

A previous bone stress injury is one of the strongest risk factors.

Other important factors include:

• Bone health

• Recovery

• Nutrition

• Energy availability

Relative Energy Deficiency in Sport (RED-S)

Bone health depends on having enough energy available to support:

• Training

• Recovery

• Hormone function

• Normal body processes

When the body consistently does not have enough energy available, this can affect bone health and increase injury risk.

This is known as Relative Energy Deficiency in Sport (RED-S).

Although often discussed in elite athletes, it can also affect recreational runners and active people balancing training with work, life stress and recovery.

Possible warning signs include:

Females:

• Irregular menstrual cycles

• Missing periods

• Delayed onset of menstruation

Males:

• Reduced libido

• Reduced morning erections

Everyone:

• Persistent fatigue

• Recurrent injuries

• Digestive issues

• Declining performance

Winter, Vitamin D and Bone Health

During New Zealand winters, reduced sunlight exposure can contribute to lower vitamin D levels.

Vitamin D plays an important role in calcium absorption and bone health.

However, vitamin D is rarely the only factor involved.

Bone health depends on a combination of:

• Appropriate training load

• Nutrition

• Recovery

• Sleep

• Hormonal health

Strength Training Helps Build Stronger Bones

Running provides an important loading stimulus for bone.

However, strength training also plays a valuable role.

Muscles create forces through bone that encourage adaptation and improve resilience.

For runners, maintaining strength throughout the year can help support:

• Calf capacity

• Hip strength

• Lower limb control

• Running efficiency

The goal is not simply to run more.

The goal is to build a body that can tolerate the demands of running.

When Should You Seek Advice?

Early assessment can help distinguish between:

• Bone stress injuries

• Tendon problems

• Muscle injuries

• Joint-related pain

The earlier a bone stress injury is identified, the more options there are to modify training while maintaining fitness.

Key Takeaway

Bone stress injuries do not usually happen because of one bad run.

They develop when training demands consistently exceed the body’s ability to adapt.

Build gradually, recover well, maintain strength, and listen to early warning signs.

If you develop a very specific pain that behaves differently from normal soreness, getting it assessed early can help keep you running.