What Is A Bone Stress Injury Or Stress Fracture?
We’re kicking off a journey into the world of bone stress injuries. These injuries are particularly prevalent in the running and sporting communities, especially in the lower limbs. As a Podiatrist, we encounter bone stress injuries frequently, making it essential to explore what these injuries are and how they typically present within the running population.
What Are Bone Stress Injuries?
Bone stress injuries (BSIs) occur when the skeleton fails to remodel itself quickly enough to cope with the repetitive loading activities typical in sports like running. Essentially, the bone's ability to repair itself lags behind the damage being inflicted upon it by continuous stress. This imbalance can lead to a range of issues, from early stages of bony stress (bone oedema) to full fractures.
Previously, many people referred to these injuries as stress fractures. However, the term "bone stress injury" more accurately reflects the continuum of damage that can occur, starting from minor bone stress and potentially leading to fractures. This distinction is crucial, as not all bone stress injuries result in fractures.
How Do Bones Work?
To understand BSIs, it’s important to grasp how bones function at a physiological level. Bones thrive on weight-bearing activities, responding positively to load by going through a cyclical process of breakdown and rebuild. This process involves two types of cells and is constantly occurring:
1. Osteoblasts – These cells are responsible for building new bone after it has been subjected to loading.
2. Osteoclasts – These cells break down old or damaged bone tissue to make way for new growth.
The balance between these two processes is delicate. When the breakdown process outpaces the rebuilding process, it can lead to conditions like osteopenia or osteoporosis, particularly in older adults who may not engage in sufficient weight-bearing activities.
For athletes, especially runners, this balance is crucial. High-impact activities like running, jumping, and hopping apply significant load to bones, which is generally beneficial. However, problems arise when the bone is unable to recover quickly enough, leading to a bone stress injury.
How Do We Grade a Bone Stress Injury?
Bone stress injuries are graded on a scale from 1 to 4, based on the severity of the damage:
- Grades 1 to 3: These stages are characterised by swelling, either on the outer or inner aspect of the bone. These early-stage injuries are challenging to detect with imaging, as they may not show up on x-rays.
- Grade 4: At this stage, the injury is more severe, with visible swelling and disruption of the bone cortex. This may appear as a fracture or increased bony callus on x-rays.
Diagnosing these injuries early is crucial, and MRI is the gold standard for detecting and grading BSIs. Early detection allows for more accurate prognosis and treatment planning.
What Are Common Sites for Bone Stress Injuries to Occur?
BSIs are most commonly found in the lower limbs, particularly in the metatarsals (the long bones in the foot) and the tibia (the shinbone). Interestingly, the most frequent site for BSIs in runners is between the second and third metatarsals. Statistics indicate that 77% of BSIs in men and 50% in women occur in the metatarsals or tibia. Women are also more susceptible to BSIs in areas like the pelvis and femur, which are higher up in the body.
What Are Risk Factors for Bone Stress Injuries?
Several factors increase the risk of developing a BSI. Here are some of the most significant:
1. Previous Bone Stress Injury: A history of BSI is a strong predictor of future injuries, with individuals at six times the increased risk of recurrence. Shockingly, one in three people who suffer a BSI will experience another within 12 months.
2. Genetics: The shape, density, and firmness of your bones are influenced by genetics. While we can't change our genetic makeup, understanding it can help in managing risk.
3. Pre-Puberty Activity: Early specialisation in a single sport, particularly those involving repetitive movements like running, can lead to lower bone density and a higher risk of BSIs later in life. Multi-directional sports, like basketball or soccer, are more beneficial for building strong bones during childhood.
4. Gender: Females are at a greater risk of BSIs than males, due to anatomical differences, hormonal factors, and other variables.
5. Low Energy Availability (LEA): This condition, also known as Relative Energy Deficiency in Sport (RED-S), occurs when the calories consumed are insufficient to meet the energy demands of physical activity. LEA significantly increases the risk of BSIs, especially in competitive athletes.
Bone stress injuries are complex and multifactorial, requiring careful management to prevent recurrence. Over the next few blog posts, we’ll dive deeper into the specifics of BSI management, diagnosis, and prevention strategies. If you have any questions or need assistance with bone stress injuries, please don’t hesitate to reach out. Stay tuned for more in our mini-series on bone stress injuries!
Have a bone stress injury? Book Now.