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Stress fractures are a common occurrence particularly in sporting endeavours and in recruits in the armed services, with overuse of the lower limbs a common theme. The lower leg is the most frequently affected area but other parts, even the arms, can be affected. The tibia, fibula and metatarsals are the most obvious areas to suffer, with further up the lower limbs much less commonly occurring. Repetitive stresses to the bones of a level not sufficient to cause direct fracture are the underlying cause of this injury.

The affected area may be the source of increasing pain levels during exercise and activity, with the sufferer often reporting they have increased their training levels in intensity or frequency. Conservative treatment is usually straightforward with limitation of activity of the part and in some fractures immobilisation is required. Healing is often also straightforward although there is the danger of non-union in some fractures, with some needing internal fixation. Orthopaedic fixation and careful immobilisation will lead to healing in the vast majority of cases.

A stress fracture is likely to occur when bone is stressed many times in a similar manner, mostly without any particular individual event occurring. As repetitive compression and tension stresses are applied to the bone it sustains micro-damage which is repaired continually by the bone remodelling process. If the bones sustain increased levels of microscopic injury they may not be able to repair themselves quickly enough by remodelling and strengthening, leading inevitably to fracture. Increased physical activity is a common factor in these injuries.

Risk factors for this injury include the elevation in how often the stresses occur, the raising of the strength of those stresses or a change in the tissue areas to which the forces are being applied. If the cross sectional area of bone which is being stressed is smaller then this will cause an increase in the stresses through that area, or the area can stay the same and the force be increased. Jumping and running are activities with a higher risk along with changes in the way activities are performed or the type of surface used.

The important issues in being a risk for stress fracture are assumed to be the mechanical factors already mentioned but there may be many others such as a lower intake of calories, a lower bone density or osteoporosis, female gender and weakness of muscle. An increased incidence of stress fractures occurs in women who run a lot and these types of female athletes and others such as ballet dancers may have menstrual cycle alterations, bone density loss and a typically low body weight so they can easily pursue their activity.

Stress fractures present with unexpected onset whilst undergoing an activity, worse as the limb is loaded repetitively, without any traumatic occurrence. When the patient rests the pain will ease and be absent but will recur once the aggravating activity is restarted. The area around the fracture will be tender and perhaps swollen, with x-ray findings elusive initially, perhaps taking two to four weeks to become apparent. Bone scanning can be more sensitive to finding a stress fracture within three days of the initial event, but can be positive for other reasons.

Conservative treatment is the typical management for stress fractures, with stopping or greatly decreasing the troublesome activity over four to six weeks the initial choice. If patients have significant pain on walking they can be given a below knee plaster, a walking boot or a brace for a similar period of time, using crutches if helpful. The use of in shoe orthoses has been studied and found to reduce the incidence of fractures to some degree, with shock absorbing insoles also perhaps helping prevent these injuries.

Stress fractures in most areas of the body heal without complications but in some cases healing can be delayed or not occur at all, so-called non-union. Delayed or non-union is more common in certain areas such as the bases of the second and fifth metatarsals in the feet. Routine review of these fractures is important to assess whether further immobilisation or internal fixation is needed.