What is a stress fracture: Normal bone responses to repetitive stress can be divided into: normal response, stress reaction, and stress fracture.
Normal response: Osteoclasts are bone cells that remove bone tissue known as ‘bone resorption’. Whilst osteoblasts are cells that create ‘bone formation’. Bone is a dynamic tissue that is constantly being reshaped by osteoblasts and osteoclasts working in balance.
Stress fracture: A stress fracture is when the repeated stress and imbalance continues and the microfracture progresses into a true break in the cortical bone.
How are they diagnosed: A clinical examination of factors such as training loads, biomechanics, location of pain, and bony tenderness, will indicate whether a bony stress reaction / fracture is a possibility. Following this various imaging options are MRI (which can show bone marrow oedema in stress reaction stages and microfractures once stress fracture develops); CT scans (not as sensitive as MRI and have associated radiation as per an XRay); Xray (which frequently doesn’t show up stress fractures in the early stages – up to 3 weeks); and bone scans (very good at detecting stress fractures but are time consuming, nonspecific and are a poor choice to monitor recovery).
Who is most at risk: The female athlete triad is a combination of low bone density, nutritional issues, and menstrual irregularities. Together these represent the highest risk of developing stress fractures in the female runner. However any one of these alone can also lead to a stress fracture when combined with running.
What else increases your risk:
- Rapid increase in running distances
- Lack of rest / recovery time during a period of running training
- Inappropriate footwear relative to the foot type of the individual
- Nicotine smoking
What to look out for:
- Pain during or after running / exercise
- Bony tenderness
- Nutrition – how balanced is your diet
- Training – running distances per week and speed of increases
- Bone density – do you know yours? (especially if you are female and run a lot)
- Shoes – despite the debates surrounding ‘support’ vs ‘free’ shoes, the right type of footwear is important for a lot of people!
Management: If you have pain with running organise an assessment as soon as possible. The best management is prevention but if they occur the treatment depends on which bone it is. Some stress fractures have greater risks associated and need orthopaedic specialists involved, whilst others are lower risk and can be managed conservatively. The most common strategy is to immobilise the area and often to remove any weight bearing stress through the bone.
McCormick et al (2012), Stress fractures in runners. Clin Sports Med, 31.