Runners and Bone Stress Injuries
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Introduction (what they are)[edit | edit source]
Bone Stress Injures occur when the bone stresses applied during activity, like running, exceed the bone's tissue tolerance. They most commonly occur in competitive cross-country runners and track-and-field athletes. [1]
Mechanism of Injury[edit | edit source]
With an increase in external mechanical factors, there are adaptive changes in internal architecture. With the increased load, a stress reaction would occur with the presence of periosteal edema. A bone stress fracture would be indicated by a cortical fracture line on the MRI. [1]
Bones have a stronger compressive tolerance, and have a greater conservative recovery.
One mechanism indirectly related to running, but relating to athlete health, are gonadal hormone irregularities, which can cause athletes to have cortical and trabecular BSIs and/or osteopenia or osteoporosis. This can also occur in athletes with nutritional imbalances, hormonal influences, and decreased bone mineral density. [1]
Risk Factors and Prevention[edit | edit source]
With mitigating or preventing risk factors of BSIs, healing times and overall bone health can be improved for runners. [1]
There are two types of risk factors that can be considered for BSIs: factors that alter the load applied to the bone, or factors that influence the bone's ability to withstand load, thus minimising damage. The factors that alter the load stem from the size, frequency, duration, and direction of the load applied to the bone. Factors that contribute to withstanding the load applied to the bone include the bone mass, size, and intrinsic properties of the bone. Intrinsic biomechanical factors that can alter bone load is foot type, leg length, or leg length differences. Other factors include, training parameters (volume, intensity, duration, or race frequency), and footwear (type and age of shoes and support). Factors that allow the bone to withstand load include athletic history/ lifestyle history, medical and family history, and Relative energy deficiency in sport, bone health, and calcium and Vitamin D status. [1]
Concerning static biomechanical factors, leg length differences, a reduced calf girth, or pes planus or pes cavus can contribute to BSIs through altered bone loading. Dynamic risk factors that can contribute include increased vertical loading, a greater peak acceleration, increased peak free mass, increased peak adduction, knee internal rotation, knee abduction, tibial internal rotation, and rear foot eversion. [1]
Regarding training patterns, the risk of BSIs can be greater with an increase in velocity, duration, distance, or frequency. [1]
Studies have shown that runners modify their leg stiffness when running on different terrains. This helps balance out ground reaction loading forces on the lower limb. Changes in running surface, terrain, and hills could also be contributors to causing BSIs. [1]
Running footwear is also a very important topic with the prevention or contribution to BSIs. Please read Shoe Analysis - Fitting a Shoe and Shoe Analysis - Anatomy of a Running Shoe for a further explanation and analysis on the fitting and suitability of a running shoe.
When talking about athletic history and medical history, it is seen that with a history of long distance running, there is an impact of lower loads, which doesn't seem to improve bone health. In addition, adolescents who take part in high-impact and multi-directional loading sports can improve bone density and geometry. [1]
Other risk factors for BSIs include a history of fractures, the use of medications or other drugs, genetic factors, or family history. [1]
Risks of BSIs[edit | edit source]
Risks in different groups[edit | edit source]
A study showed that in an adolescent age group, there was an increased risk of BSIs with more than 32 km/week of running. However, as mentioned above adolescents taking part in high-impact and multi-directional ball sports such as basketball or soccer have a protective effect toward stress fractures as adult runners. [1]
The Male Runner[edit | edit source]
Similar to the female triad (mentioned below), male runners can experience low energy availability, hypogonadotrophic hypogonadism, and low bone mineral density. Multiple risk factors in males, similar to the female triad, can have an accumulative risk of BSIs
Low energy availability can occur from eating disorders, inadequate nutrition, or expending more calories than being taken in. With low energy availability or high volume training, can cause changes in the hypothalamic-pituitary-gonadal (HPG) axis. A study by Hackney et al shows that endurance runners have a lower testosterone level than sedentary individuals. A study by Wheeler et al showed that an increase in running mileage had an inverse relationship to testosterone levels.
RED-S, which can occur in males or females, results from inadequate caloric intake or excessive expenditure of energy. This can be disadvantageous to bone health, impair metabolism, menstrual function in females, immunity, protein synthesis, cardiovascular, and psychological status.
The Female Runner[edit | edit source]
There is an Energy Availability Triad for females, which is outlined by the integration of energy availability, menstrual function, and bone mineral density. A female runner may have deficiencies in any of the triad factors. Having more triad factors leads to an increased risk of BSIs.
A dual-energy x-ray absorptiometry (DEXA) is the principle method used to measure bone mas density. A DEXA is indicated if the woman is <17.5kg/m^2, menarche >16 years, eating disorder history, 2 prior BSI, or one high-risk BSI.
Diagnosis[edit | edit source]
BSIs can be detected from MRIs of periosteal edema as well as differing levels of bone marrow edema. More severe injuries may be indicated by a cortical fracture line on the MRI. [1]
Upon noticing these symptoms, early identification and management would lead to better prevention of further injury. [1]
Management[edit | edit source]
The primary goal of healing would be to work towards pain free movement and gait, and abrupt movements. Low risk BSIs can be managed through immobilisation or modification of activity to work towards pain free movement. Medium or high risk BSIs ...
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