Bone Stress Injuries

Overuse injuries happen in marathoners for a variety of reasons, including physical qualities of the runner, hereditary factors, technical factors, and even psychosocial reasons.  The bottom line is, if your training outpaces your rest and recovery, your body breaks down and an injury develops. 

 This process is known as the Mechanical Fatigue Model of Overuse Injuries, pictured below:

 Edwards, WB. Exerc. Sport Sci. Rev., 2018

 When a training load is applied to your tissues, it results in stress or strain.  This can be good: if the damage that forms from the load is balanced by the body’s mechanisms for removal and repair, remodeling or adaptation occur.  That’s the process by which you gain fitness.  However, if the amount of stress or strain is too much, or if it occurs too frequently or for too long, total damage overwhelms your body’s adaptive mechanisms, and you get injured. 

 What does this look like for bone?  The diagram below illustrates how a bone stress injury develops:

Sharma J and Heagerty R. J Fractures and Sprains, 2017

 Microtrauma to bone starts to accumulate, resulting in swelling and inflammation in the bone.  Ultimately, this becomes a “stress reaction”, which is weakening of the bone that can progress to a full-blown crack, or stress fracture.  You might feel pain in the affected area, at first only with running.  If you ignore it, you may then start to feel it with regular walking and activities of daily life.  Vulnerable areas in runners are the feet, the lower leg and the hip.  Less commonly, stress reactions or fractures can happen in runners in the spine. 

 It’s important to catch the injury while it’s still a stress reaction, before it becomes a fracture.  Most stress reactions heal well in 6-8 weeks, but if it progresses to a fracture it can take significantly longer – often about 3 months.  You can avoid this kind of injury by making sure you move forward with your training gradually.  Give yourself enough time to adapt to the frequency, amount and intensity of running you want to do.  Make sure to mix in rest days, cross-training and strength training. 

 Many runners don’t realize how much a suboptimal diet puts them at risk for developing bone stress injuries.  Eat a balanced diet and make sure you are getting adequate calories for the amount of exercise you are doing.  Also pay attention to your intake of calcium and vitamin D.  If you don’t eat much dairy, I recommend an over the counter supplement of 500 mg calcium along with 400 IU Vitamin D, taken twice daily. 

If you’re worried you have a stress reaction or stress fracture, you will be diagnosed by an imaging study.  Usually x-rays are the first imaging study we check, but if the bone stress injury is in an early stage, we may not see it on an x-ray.  If that’s the case, we’ll need to get an MRI.  MRI can show early swelling and damage in the bone before it cracks.  If we diagnose a bone stress injury, our first priority will be to protect it so it can heal.  You may have to wear a walking boot, or use crutches, until you stop having pain.  You will also have to cross-train with low- or non-impact activities until the injury heals. 

 Bone stress injuries are a frustrating part of distance running that many runners have to deal with.Now that you’re armed with a little information about them, I hope all of you can avoid them this training cycle!