A stress fracture is a small crack on the external surface of a bone. It’s called a stress fracture because it occurs when the bone is repeatedly put under some sort of stress, typically during weight-bearing exercise, such as running, ballet dancing, or basketball, and typically after a sudden large increase in exercise levels. (A stress fracture can also develop after normal activity if the involved bone is weakened by a condition like osteoporosis.)
Occurring most often in the lower extremities, especially the tibia (shinbone) or the metatarsals (long bones in the foot just before the toes), stress fractures are considered overuse injuries because it’s not one event that causes them but rather repetitive ones.
These fractures are fairly common: About 10 percent of injuries seen in competitive and recreational athletes are stress fractures of the ankle or foot.
The most common symptom of a stress fracture is pain upon weight bearing that increases with activity. There is often tenderness at the location of the fracture and soft-tissue swelling in the surrounding area. The pain usually comes on slowly over a few days or weeks and worsens if normal activity is continued.
Stress fracture risk factors
Normally a bone adapts to loading from bearing weight by gradually remodeling its structure to become stronger. But if the loading forces increase to a point beyond what the bone can tolerate, microinjuries to the bone occur. If the excessive loading continues, the bone repair and remodeling processes cannot keep up with the repetitive microinjuries, and the result can be a stress fracture.
Women are at a higher risk for stress fractures than men, possibly in part because of their generally lower bone mineral density and their lower muscle mass. Eating disorders (more prevalent in women) and irregular menstrual cycles can negatively impact bone health, too, and may also partly account for the sex discrepancy. In addition, women may be more susceptible due to anatomical differences. For example, because of a wider pelvis, women’s thigh bones angle inward more sharply from hip to knee, which increases stress on the tibia and foot bones.
Other factors that are thought to play a role in stress fracture risk include abruptly changing your weight-bearing exercise routine (such as increasing its frequency, intensity, or duration), overpronating (rolling on the inside of the foot), exercising in worn athletic shoes, working out too frequently, and having a prior stress fracture.
A study published in June 2019 in Medicine & Science in Sports & Exercise debunked the notion that running faster—which is thought to put more strain on shin bones—contributes to stress fractures more than running slowly. It included 43 recreational runners who ran three laps around a track at a slow, moderate, or fast pace. The track had sensors that measured the force on the runners’ shins as they made contact with the ground. The greatest load on the tibia occurred when the subjects ran at the slowest pace, not the fastest as was expected, perhaps because, as the researchers hypothesized, each foot remains on the ground for a longer time at the slower speed. Running at moderate pace resulted in less load overall on the tibia, compared with both fast and slow speed.
Recovering from a stress fracture
If you think you have a stress fracture, see your health care provider, who may order an imaging test. X-rays can be helpful, but they often remain normal for two to three weeks after the injury. An MRI can help determine not only the presence of a stress fracture but also its severity.
For some stress fractures, you may need to wear a walking boot or a brace or use crutches for a while. This reduces the weight-bearing load until you can walk and do normal activities without pain. When you resume exercise, you will probably need to modify your routine so that you can work out without pain. Most often, that means stopping high-impact workouts until the bone heals.
How long full recovery takes depends on many factors, including the site and extent of the fracture, but it can be as long as two to six months. Rehabilitative exercise and cross-training may aid in recovery. Therapeutic ultrasound, shock wave therapy, and electrical stimulation have mixed or uncertain benefits.
Reporting contributed by Jeanine Barone. This article first appeared in the UC Berkeley Wellness Letter.
Also see Get Fit Without Getting Hurt.
Published October 14, 2019