What is a stress reaction or stress fracture?
A stress reaction can be considered similar to a deep bone bruise, which arises from trauma or overuse. Stress injuries can be classified on a spectrum upon diagnosis: early (stress reaction) or late (stress fracture). A stress reaction that goes untreated will develop into a stress fracture. In a stress fracture, a small crack develops from repetitive trauma, which is usually caused by overuse. Overuse injuries account for almost 50% of all sports injuries.
Where do stress fractures happen?
Stress fractures can occur anywhere there is overuse, but they’re most commonly found in the lower extremity as a result of impact and weight bearing activities. The most common bone is the shin bone or tibia (20% to 75% of all stress fractures — often running injuries). Stress fractures can also occur in the foot. The foot is made up of several small bones. The bones running to the toes are called metatarsals. There are five metatarsals in each foot. It is most common for a stress fracture to happen in the second and third metatarsals. Stress fractures can also be seen in the heel (calcaneus), hip (proximal femur) and even the lower back.
What causes a stress fracture?
Risk factors for stress fractures can be divided into two basic categories: extrinsic and intrinsic.
Extrinsic factors happen outside of the body. These can also be called environmental (nature) factors. These factors can include:
- Practicing incorrect training or sport technique.
- Having too rapid of a training program or volume of activity or changing your activity level without a gradual break-in period.
- Changing the surface you exercise on, such as going from a soft surface (like an indoor track) to outside on gravel or concrete.
- Running on a track or road with sloped surface.
- Using poor equipment or improper footwear (shoes that are too worn out, too flimsy or too stiff).
- Doing repetitive activity in certain high-impact sports, such as:
- Long-distance running (tibia, hip).
- Track and field.
- Gymnastics (wrist stress fractures from weight bearing on hands/wrists, low back).
- Dance (feet, low back).
- Having a poor diet that has inadequate caloric intake for volume of sport.
- Having a low vitamin D level.
- Experiencing early specialization in sports. Youth who play one sport year-round without a break are at risk of stress fractures.
Intrinsic factors are things that are related to the athlete or patient and aren’t impacted by outside forces. These factors can include:
- Age: Older athletes may have underlying bone density issues such as osteoporosis. Already weakened bone will develop a stress reaction and/or fracture sooner than healthy bone.
- Weight: Both ends of the spectrum seem to be at risk for stress injuries. Someone with a low BMI or underweight individual may have weakened bones and someone with a high BMI doing repetitive loading with their body weight would also be at risk for injuries.
- Anatomy: Foot problems can affect the way the foot strikes the ground. These foot problems can include bunions, blisters, tendonitis, and low or high arches. Muscle weakness, imbalances or lack of flexibility can also be a factor.
- Sex: Females may be at risk if they have irregular menstrual periods or no periods.
- Medical conditions: Osteoporosis or other diseases that weaken bone strength and density (thickness). The weak or soft bones may not be able to handle the changes in activity.
What are the symptoms of a stress fracture?
The symptoms of a stress fracture can include:
- Pain, swelling or aching at the site of fracture.
- Tenderness or “pinpoint pain” when touched on the bone.
- Pain that begins after starting an activity and then resolves with rest.
- Pain that’s present throughout the activity and does not go away after the activity has ended.
- Pain which occurs while at rest, during normal activity or with everyday walking.
- Pain which is worse with hopping on one leg or an inability to shift weight/hop on affected leg/foot.
If a stress fracture is not treated at an early stage (stress reaction), the pain can become severe. There is also a risk that the fracture may become displaced (the fractured bone moves out of normal alignment). Certain stress fractures (hip) are considered “high risk” stress fractures because they may have a poor outcome (such as needing surgery) if not identified early.