ACSM Sports Medicine Basics Stress Fractures www.acsm.org

Incidence Bone adaptation occurs via increased will render a bone temporarily weaker until Stress fractures and other bone stress injuries modeling and/or remodeling. Modeling replacement bone can be deposited and comprise up to one-sixth of all athletic injuries is a response to chronically increased or mineralized. Untimely loading during this and have been reported in virtually all bones decreased loading when bone tissue is either window of reduced bone strength may lead of the body. Athletes most at risk of stress deposited or removed in order to modify the to more microdamage and the coalescence of fracture are runners, jumpers, gymnasts and shape and/or size of a bone. The addition damage into one or more stress fractures. dancers, for whom the lower extremity is most of bone tissue around the perimeter of a commonly affected. Vertebral stress fractures long bone shaft will increase its resistance Risk Factors occur in cricket, fast bowlers and gymnasts, to bending and is therefore an adaptive Many factors have been purported to while upper extremity stress fractures are response to exercise that is likely to reduce contribute to the risk of stress fracture, but typically reported in swimmers, rowers and the risk of stress fractures. Remodeling quality evidence to support those claims is racquet sport players. Lower extremity stress involves bone resorption followed, after a often lacking. The best available evidence fracture incidence among military recruits delay, by deposition of replacement bone. suggests that a change in training, low fitness is slightly higher than in athletes, with The remodeling process occurs continuously and low muscle strength will increase the particularly high rates reported for females. throughout life in order to mobilize calcium risk of stress fracture. There is conflicting for numerous essential physiological processes. evidence that female sex, low bone mass, Etiology Remodeling is upregulated under a variety of low serum vitamin D, and narrow bones Exercise-related loading causes a degree of metabolic conditions, following exposure to predispose to stress fracture. While anecdotal deformation (strain) in bone. Bone exhibits certain drugs, and in response to load-induced reports or findings from lower quality studies an intrinsic ability to adapt to changes in microdamage. Resorption (by osteoclasts) have suggested age, race, pes planus (flat feet), patterns of strain (magnitude or type) in acts to remove damaged bone, after which pes cavus (high arch), genu valgus (knock order to minimize excessive deformation that osteoblasts deposit replacement bone. This knees), leg length inequality, tall thin body may cause microdamage. Bone also has the “self-healing” characteristic of bone is a type, reduced flexibility, inadequate calories, capacity to repair itself. Ironically, for some remarkable phenomenon that maintains the inadequate calcium, previous injury, alcohol, the processes of adaptation and repair may integrity of the skeleton, but its success can smoking and corticosteroids are all associated transiently increase the risk of stress fracture, be compromised by excessive loading during with increased risk of stress fracture, no robust as described below. the resorption phase. That is, the initial human data exists to support those claims. increase in porosity from increased resorption 3. Resume training gradually, restarting at lower intensity than when injured 4. Use pneumatic braces for long bones as they may be helpful during return to training

When injured, do not: 1. Completely immobilize the injured site 2. Engage in activities that generate pain at the injured site 3. Engage in heavy resistance training of the injured site 4. Take pain medications if avoidable

New Directions Preliminary evidence suggests that low intensity pulsed ultrasound may enhance stress fracture healing. Electrical or electromagnetic stimulation may also be helpful, but more data is needed. The benefit of training in bare feet or minimal shoes requires further investigation.

Summary Stress fractures are a recognized complication of chronic, intensive athletic and military training. Bones are most susceptible Diagnosis stretching, taping and massage will not to stress fracture when weakened by Positive symptoms of stress fracture include enhance the rate of healing. Prevention is remodeling-related porosity – a primary local tenderness, pain with loading, pain undoubtedly the best management approach. stage in the adaptive or restorative response with direct or indirect percussion, and the of bone to changes in patterns of loading presence of night pain. Confirmation of Recommendations to minimize the risk of or microdamage. Prevention is the most clinical diagnoses with imaging can be fraught stress fracture and promote recovery include appropriate management approach, best due to false positives and negatives, however the following: achieved through graduated training triple phase technetium99 bone scans are increments to maximize muscle strength and Before beginning or substantially modifying generally highly sensitive to stress fracture. general fitness. Adequate nutrition, including training: Magnetic resonance imaging (MRI) is now calcium and vitamin D is also important. 1. Ensure old injuries have been fully considered to provide the best impression While bone scans and MRI can be used rehabilitated (particularly if the individual of injury severity due to the ability to to detect stress fracture, clinical diagnosis has been immobilized for any length of differentiate periosteal and marrow edema; is normally adequate. The goal of stress time) the latter being indicative of greater severity. fracture treatment is to temporarily reduce 2. Enhance muscle strength around Plain radiographs and CTs are inadequately loads on the injured site to prevent further chronically loaded bones sensitive for the purposes of diagnosis. microdamage and allow the bone tissue to 3. Ensure adequate nutrition, calcium and Ultrasound and tuning forks are similarly remodel. Thus, rest from pain-provoking vitamin D inadequate diagnostic modalities for stress activities remains the most effective, if often prolonged, intervention approach. Clinical fracture. Generally, historical symptoms During training: and physical signs provide adequate bases resolution of symptoms is the most reliable 1. Increase training intensity or alterations guide for timing of return to training. Return for diagnosis. Imaging signs can also be gradually over a period of four to six weeks, misleading in terms of recovery; therefore the to full training intensity must be highly depending on the nature of the training graduated. clinical resolution of symptoms provides the 2. Ensure correct technique to minimize bone best guidance for return to training. impact About the Author Management Recommendations 3. Run initially on very uniform surfaces, such Written for the American College of Sports Medicine by as level, short grass or asphalt. Progress Belinda R. Beck, Ph.D. As stress fractures are typically a consequence to longer grass, soft soil, sand and uneven Suggested Citation: Beck B. Stress Fractures. Indianapolis, IN: of the normal adaptive or restorative response American College of Sports Medicine; 2016. terrain, thereafter varying the training of bone to modified loading, unloading ACSM Sports Medicine Basics are official statements by the surface. American College of Sports Medicine concerning topics of interest (rest) and graduated return to training is 4. Maintain a minimum of 1000 mg/day to the public at large. ACSM grants permission to reproduce this fact the most effective method of treatment in sheet if it is reproduced in its entirety without alteration. The text dietary calcium and 800 IU/day vitamin D may be reproduced in another publication if it is used in its entirety most circumstances. Recovery times vary without alteration and the following statement is added: Reprinted according to site with small bones healing When injured, do: with permission of the American College of Sports Medicine. more quickly than large, and some locations Copyright ©2016 American College of Sports Medicine. Visit 1. Rest from pain-provoking activities at the ACSM online at www.acsm.org. being particularly problematic (e.g. anterior first sign of bone discomfort, and resume tibia, superior femoral neck) As there is some offending activity only when pain-free with evidence that non-steroidal anti-inflammatory loading drugs (NSAIDS) and even acetaminophen are 2. Maintain aerobic fitness with exercise that disruptive to bone healing, pain medications does not overload the injured bone should be avoided when possible. Ice,