July 18, 2001 -- Weekend warrior or serious competitor, we can all fall victim to stress fractures, small but painful bone weaknesses caused by repetitive stress. Such fractures are responsible for an estimated 10% of all sports overuse injuries.
William O. Roberts, MD, a family physician at MinnHealth, in Minnesota, and vice president at the American College of Sports Medicine, likens a stress fracture to bending a paperclip back and forth: "Eventually you get little cracks."
While stress fractures are pretty common in the lower extremities -- the shin, foot, ankle -- they can also occur in the back or in the arms, says Nicholas A. DiNubile, MD, an orthopaedic consultant to the Philadelphia '76ers and the Pennsylvania Ballet.
Both Roberts and DiNubile say overtraining is the main reason people develop stress fractures. But beyond that, "any sudden change in the intensity, duration, or frequency of training program" can also place an athlete at risk, says DiNubile.
In most cases, treating a stress fracture can be summed up in one word: rest.
"Treatment usually is to stop the offending activity," says DiNubile, adding that more severe stress fractures may need to be treated with a cast, or in rare instances, with an operation.
But resting doesn't mean giving up all training. Both Roberts and DiNubile say athletes can continue to work out. "Keep conditioning up by low impact alternatives," says DiNubile, like swimming or cycling.
"Also you need to deal with any biomechanical factor," says DiNubile, referring to individual physical traits that could interfere with motion. "For example, get a lift if your legs are uneven, or custom orthotic insoles if your arch is problematic," he says. "And make sure that your training program is a gradual one. We use the 10% rule: Don't increase a training program more than 10% each week. That allows your body to adjust and accommodate and react to the new stresses."
Roberts adds good nutrition and calcium supplementation to the list of treatments, along with estrogen supplementation for women with low estrogen. "And there are some newer treatment modalities that are coming down the pike, such as ultrasound or magnetic field stimulation of the site," he says.
While stress fractures are common, recurrent fractures are less so. To find out why some athletes are more susceptible than others to repeated fractures, a Finnish research team recently completed a comparative study of the anatomies, nutritional history, training programs, bone mineral densities, and hormonal histories of 31 athletes with multiple stress fractures and 15 athletes without fractures.
Among male athletes with repetitive stress fractures, 70% of the fractures were in the two bones that make up the lower leg; in women, 50% of the fractures were in the foot and ankle. The majority of patients, 60%, were runners.
The researchers found that certain biomechanical factors were associated with multiple stress fractures, including a high foot arch, leg-length inequality, and excessive inward turn of the foot. Forty percent of the fracture-prone women reported menstrual irregularities, compared with about 7% in the control group. Runners with high weekly training mileage were also found to be at greater risk.
The study runs in the May/June issue of The American Journal of Sports Medicine.