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.

Increasing levels of pain reported in the part during activities or exercise is the typical pattern of presentation, with a recent upturn in the intensity or frequency of training often reported. Treatment is uncomplicated and involves reducing the levels of activity and in some cases by immobilisation. Most heal without problems but there are some fractures which are much more likely to suffer from non-union and for which surgical intervention may be required. With orthopaedic surgery and formal immobilisation these fractures will eventually heal.

Stress fractures happen when bone is repetitively loaded and this type of fracture is not usually the result of any particular traumatic occurrence. On being stressed with repeated tension or compression loads bone adapts by remodelling its structure and repairing the stress induced damage. If more of the microscopic damage to the bone occurs than can be repaired by the remodelling process then a fracture may occur. Significant increase in the person’s recent physical training is a common theme.

The risk factors include an increase in the frequency of the applied stresses, an increase in the intensity of those stresses or a change in the area to which the stresses are being applied. If the surface area of the bone to which the stress is applied is reduced then the absolute stresses through those bony areas increase, or the load may be absolutely increased. Running and jumping are examples of more high risk activities, as may be changes in performance technique or in the nature of the surface exercised upon.

Additional factors could be risk factors such as reduced bone density, dietary changes, weakness or other mechanical factors as the other factors are all mostly presumed to be the key ones. Scientific research has indicated being female, having a low body weight, poor diet and many other factors may be important. Female runners are particularly at risk, with reduced caloric intake, disturbances in menstrual cycle and lower bone density presenting in such athletes and others who require a low body weight such as ballet dancers.

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.

Stress fractures are mostly treated with conservative methods, the most effective and the most straightforward being to limit the aggravating functional activity responsible for a period of four to six weeks. If weight bearing causes significant pain then it can be restricted by using elbow crutches with a rigid walking boot, brace or below knee plaster cast. Studies have been done on wearing corrective orthoses in shoes and there is some evidence they can reduce the incidence of stress fractures, with some potential benefits from shock absorbing insoles

Typical healing of stress fractures is uncomplicated but there is a risk of the fracture suffering from poor healing or non-union in particular bodily regions. The fifth and second metatarsals can suffer from delayed or lack of healing at their bases and as such should be reviewed in case more controlled immobilisation or surgical intervention is required.

Jonathan Blood Smyth, editor of the Physiotherapy Site, writes articles about Physiotherapists, physiotherapy, physiotherapists in London, back pain, orthopaedic conditions, neck pain and injury management. Jonathan is a superintendant physiotherapist at an NHS hospital in the South-West of the UK