Overuse injuries develop when repetitive stresses to bone and musculo-tendinous structures are applied and cause changes that damage tissue at a greater rate than that at which the body can repair itself. A combination of extrinsic factors, such as training errors and environmental factors; and intrinsic or anatomical factors, such as bony alignment of the extremities, flexibility deficits, and ligamentous laxity, predisposes athletes to overuse injuries . Lower-extremity stress fractures are common injuries most often associated with participation in sports involving running, jumping, or repetitive stress, such as in soccer . Stress fracture is the consequence of bone structure failure after repeated micro-traumas. The effect of repeated injuries is stronger than bone remodelling potential. Different populations can be affected, and different patterns of insufficiency fracture can be seen related. Also among athletes, differences in terms of sport specialty, morphotype of the athlete, age, and race, must be considered [3, 4]. Many different factors are involved in generating a stress fracture : - Running is the most important factor in stress fracture of the inferior limb; 84% of inferior-limb stress fracture in athletes is related to running. Furthermore, a sport-specificity of injury must be considered. Specific actions involved in a particular sport determine site and type of fracture. As described, the specific way of running in soccer influence the typical stress fracture related to this sport (of the metatarsal bone). - Frequency, speed, and amount of load, as well as recovery time between load phases, are important. In athletes, risk of stress fracture increases proportionally to load increase. This risk is related to muscular fatigue: when the buffer action of muscle fails, the impact of injuring force on bone increases. The buffer action of muscles is related to load application on bone, including control of piezo-electric activity and distribution of electrical changes. A concentration of positive changing has been consid ered a trigger factor due to stimulation of osteoclastic activity. However, muscular strength can be a risk factor, as well. For instance, in case of traction force at the muscle insertion site, the stronger the muscle, the higher the risk of stress injuries (olecranon in throwers, fifth metatarsal base in soccer players). - Vectors of load application related to bone structure are also involved. Individual anatomic features (limb length, load axis) can condition biomechanics and kinematics of sport. Abnormalities in alignment can also be important in stress-fracture pathogenesis (flat foot, valgus knee, hyperpronation). - Quality of bone related to age and gender (hormonal influence) . Stress fractures are overall more frequent in women, basically related to nutritional habits and menstrual abnormalities. Furthermore, adolescent age is a risk factor for the following reasons: articular cartilage in growing subjects (especially in elbow, knee and ankle) is particularly vulnerable; overload injuries at this level are quite frequent. Long bones and tendon-muscle unit growing speeds are not the same. This fact can lead to muscular imbalance and consequently to joint stiffness and high-traction tension at apophysis . - Ground conditions are extremely important in soccer, especially in lower series where terrain can be uneven and re-covered with uniform grass. Terrain is also subjected to changes due to weather conditions (harder surfaces in winter time) . - Other controversial issues concern materials and shoes and particularly their shock-absorbing power, which could protect the skeleton from injuring stresses. - Malalignment of the lower extremity, including excess femoral anteversion, increased Q angle, lateral tibial torsion, tibia vara, genu varum or valgum, subtalar varus, and excessive pronation, are frequently cited as predisposing to lower-limb overuse injuries .
ASJC Scopus subject areas