This is an excerpt from Run Healthy by Emmi Aguillard,Jonathan Cane & Allison L. Goldstein.
Stress fracture is a much-feared term to any runner because there is no shortcut or trick for training through one. Stress fractures respond best to rest. The goal, therefore, is to avoid them altogether. In this section, we highlight common risk factors for bony stress injury. This is not an injury to try to work through on your own. See your doctor as soon as possible if you suspect this is what you are dealing with.
Bone is the strongest structure in the body, so an injury here is slower to heal than most other running injuries. The silver lining of a bony stress injury is that although bone is slow to heal, with proper rest the likelihood of reinjuring a fully healed bony injury is slim. Bones heal well, and they heal relatively simply. Your body doesn’t produce fibrous scar tissue within a bone; it simply builds more bone. For proper healing to occur, it is critical to reduce loading to the injured region and also to make sure you are getting adequate fuel to help the body reproduce the bone that it needs to lay down.
What exactly is a stress fracture? A stress fracture occurs if a bone is placed under too much load and the supporting muscles around it can no longer adequately absorb the load or impact. A stress fracture usually begins with swelling or inflammation inside of the bone, known as bony edema. If you were to get an MRI, a doctor might diagnose you with a stress reaction at this stage. Once there is fluid within a bone, the strength and integrity of the bone is compromised, and a runner is much more prone to a stress fracture, i.e., a small crack in the bone. Bones are intended to be strong and sturdy. Fluid within the bone creates a softness that can’t withstand force to the same degree.
In runners, the most common place for stress fractures are in the metatarsal bones (foot) and in the tibia (shin). Stress fractures also occur in the femur and pelvis, although these are less common. While training error or form can be a major contributor to bony stress injury, stress fractures, especially those in larger bones such as the femur and pelvis, can be a telltale sign that a runner is underfueling.
Nutrition and Bony Injury
While calcium and vitamin D are famous for bone health, evidence supports an overall lack of caloric intake to be the driving factor for recurrent stress fractures, especially in female runners (Heikura et al. 2018). If a runner is not fueling enough postrun, the body will start to break down bone in order to meet its nutritional needs, and this paves the way to bone injury. Read chapter 17 to learn more about how nutrition can contribute to injury—and to healing.
A warning sign of a stress fracture can be a consistent dull ache that does not go away as you warm up and may get worse as you run. You may also notice increased tightness in the muscles surrounding the site of injury as your body tenses up to try to protect the region. Pain that is palpable at a small, isolated spot along the inside of your shin bone or on your foot could also be a sign that you have a bony injury.
The hop test can be a useful diagnostic tool. Jump and try to land heavily on your foot. If this provokes pain (more with landing than with pushing off), chances are high that you are dealing with bony injury.
The stakes are high here. If you continue to run on a stress fracture, you risk a full-blown fracture, i.e., a snap or break of the bone, which may require surgery. If it’s a femoral neck or pelvic stress fracture, the risk of a complete break is significant. A fracture in your pelvis can result in an intensive surgery requiring metal hardware to be drilled into the hip to put the pieces of bone back together. A fracture to the femoral neck can tear the blood vessels that supply blood to the femoral head (the ball in the ball-and-socket of your hip bone), which can cause the bone tissue to die, a term coined avascular necrosis. Eventually, the entire bone can collapse. It’s not advised to train through any of these.
Risk Factors in Female Runners
Women are more at risk than men for bony injury, especially runners who have experienced amenorrhea (loss of or an irregular menstrual cycle). Amenorrhea is a sign that your body is not getting enough nutrients, and there is a significant correlation between nutrient deficiencies and risk for stress fractures. Low estrogen levels can also inhibit your body from rebuilding bone. Low-estrogen birth control taken over a long time can decrease your body’s overall estrogen levels enough to impact bone health. Working with your doctor and a registered dietitian is critical if you are amenorrheic or have low estrogen. The bottom line here is: If you aren’t getting your period, this is a warning sign from your body. It is not a normal side effect of training. Period.