Fibula Stress Fractures

fibula stress fractureA fibula stress fracture is an overuse injury that tends to affect runners or athletes in sports that require a lot of running.  It usually starts off as a dull pain on the outside of the lower leg, just above the ankle, and may progress to swelling of that region and tenderness directly over the bone. 

Stress fractures in the lower leg more commonly occur in the tibia, the larger of the two bones in the calf and the one that bears most of the weight. Athletes who under pronate or who have high, rigid arches that don’t provide adequate shock absorption. Fibula stress fractures on the other hand are more associated with flat feet, or excessive pronation at the foot and ankle. Since fibular stress breaks are less common they can easily be misdiagnosed as muscles sprains or tendinitis.

How do fibula stress fractures develop?

Stress fractures develop when there is unusual or repetitive force being applied to bone. This can occur either through the action of muscles and soft tissue around the bone exerting a pulling or twisting force on their attachment points or by heavy and sustained compressive loads.

Peroneal Muscles

It’s not clear exactly which of the two mechanisms described above cause the injury, and it’s possible that both may play a role. The peroneal muscles attach on to the fibula in the area where stress fractures tend to develop. These muscles may be under increased strain in people who overpronate.

Also, when muscles become fatigued they no longer effectively absorb shock leading to increased force being transferred directly to the bone. It’s been suggested that these muscles have to work harder during certain phases of the gait cycle in overpronators.

A number of ligaments also connect the end of the fibular to the foot that serve to stabilize the ankle. Any of these structures can cause traction forces on the fibula, especially with the repetitive bending and twisting motions that occur in the lower leg when running.

Because the fibula does not have any bony connections to the knee or ankle it’s traditionally considered a non-weight bearing joint.  Studies have shown that the fibula does carry some of the load of the body, and its contribution to load bearing increases whenever weight through the leg increases. The rolling in of the foot that occurs with over pronation causes increased compression load on the outside of the ankle which is another mechanism of injury for stress fractures, particularly in heavier runners.

How can I tell if I have a stress fracture?

Individuals with fibula stress fractures usually feel localized pain on the outside of the lower leg. The pain typically occurs with weight bearing activity although occasionally symptoms will occur when resting or at night. Some people may find that walking even short distances is enough to provoke their symptoms while others may find they are still able to be active or even run but will experience an increase in pain after activity.

With most stress fractures, pressing on the bone directly over the suspected break will produce the symptoms. Anyone experiencing pain in their lower leg that does not resolve within a week should consider getting the problem evaluated. A thorough examination by a doctor or physical therapist is usually sufficient for establishing a diagnosis. Stress fractures will sometimes, but not always, show up on x-rays. Usually evidence of a stress fracture will be seen on an x-ray after healing has already occurred. Advanced imaging like an MRI or bone scan may be helpful in confirming a diagnosis.

What can I do about the injury?

Unfortunately, once a stress fracture has developed it will require time and rest to allow the bone to heal completely. This process typically takes between 6 and 8 weeks and during that time it is best to avoid painful activities. A physical therapist may be able to provide exercises to maintain strength and flexibility while the fracture is healing, and can offer advice on how to transition safely back into activity or training.

Stress fracture prevention strategies

1. Listen to your body. Because this injury is caused by overuse the best form of prevention is to carefully structure your training or running regimen to allow adequate recovery time and avoid taxing your legs. It’s important to be in tune with your body and any type of pain on the outside of the ankle or lower leg should be seen as a sign that measures need to be taken to avoid a future injury. 

Running mechanics can change when you become fatigued during long runs. Avoid running past the point when fatigue prevents your from keeping good form.  

2. Overpronation and its related components should be given consideration when attempting to minimize the risk of this injury. These should include:

3. Increase training gradually. A good rule of thumb is to not increase your running or activity by more than 10% each week. For example, if your current weekly mileage is 15 miles, only increase that by 1.5 miles the next week.

4. Cross-train. Runners are notorious for foregoing other forms of exercise to hit their mileage goals. The repetitive nature of the running motion easily allows muscle imbalances to develop. This can be offset by substituting another mode of exercise (swimming, yoga, tennis, weight lifting etc.) for running at least once a week.

5. Appropriate footwear. The effect shoes can have on running mechanics should not be overlooked. There is a lot of debate about which type of shoe is best suited for overpronators. I personally don’t like the concept of arch supports and stability shoes that attempt to control the motion of the foot and prefer more neutral or minimalist style shoes.

People who are not used to barefoot style shoes however may actually cause stress fractures by trying to make the transition away from cushioned and highly supportive shoes too quickly. The best practice would be to use a variety of different types of training shoes and to rotate them. This way stress through the muscles and joints will be varied with each run, preventing forces from constantly being directed to only one part of the leg. Shoes that are old and show significant signs of wear should also be replaced.

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