Stress fractures are a common overuse injury. Stress fractures occur predominately in bones subject to excessive load bearing. They are a type of fracture occurring in bones that undergo mechanical fatigue over time, such as the weight bearing bones of the lower extremity. This is opposed to the more sudden (acute) failure of bone we are familiar with in other fracture types. Frequently involved bones include the tibia (shin bone) and metatarsals of the foot.
Bone has excellent strength (and some elasticity) that allows it to withstand the various forces it encounters. However, activities that involve repeated, rhythmical, sub-maximal forces such as running, dancing and frequent jumping can challenge the integrity of bone.
Bone is a living organ that continually undergoes a physiological process known as remodelling, whereby mature bone is removed (resorption), and replaced by new bone tissue (formation). When the demands placed on bone exceed its ability to remodel, an imbalance arises that may lead to a stress reaction, also known as bone bruising.
From there a fracture line develops and a microscopic breaking of the bone commences (small breaks that cannot be seen on x-ray). If this region is subjected to further loading, damage across the fracture line will increase prior to adequate healing. This leads to a larger break in the bone, although no obvious deformity may be evident.
By this stage patients usually present with a well localised, dull pain that has increased over several weeks to months. It may be difficult to describe when and how the pain started. Skin discoloration and swelling is not always present, though the site of pain will be tender when firmly pressed. Pain is first noticed at rest, then with activity, often worsening with increased activity (pain crescendo).
As the fracture lines are often too small to detect on x-ray, the use of bone scans, CT and MRI imaging may be used for diagnosis. Early diagnosis and management by an experienced health professional is essential in achieving a successful outcome.
Treatment planning depends on the location of the injury and often involves a period of complete non-weight bearing followed by partial weight-bearing in a CAM boot. Surgery is rarely indicated as these typically respond well to conservative management. To lower the risk of stress-related injuries, it is important to monitor workload. Overtraining may be in the form of excessive distance, intensity or insufficient rest within or between sessions. Minor adjustments to your weekly program may be all that is required.
There are intrinsic factors to be considered such as poor flexibility, insufficient muscle strength, altered gait pattern or running technique, anatomical variants, nutritional deficiencies (vitamin D and calcium) and poor bone density. You may also want to have your footwear and orthotic devices reviewed.