Definition
Stress fractures are tiny cracks in a bone. Stress fractures are caused by the repetitive application of force, often by overuse â€â€Â� such as repeatedly jumping up and down or running long distances. Stress fractures can arise from normal use of a bone that's been weakened by a condition such as osteoporosis.

Stress fractures are most common in the weight-bearing bones of the lower leg and foot. Track and field athletes are particularly susceptible to stress fractures, but anyone can experience a stress fracture. If you're starting a new exercise program, you may be at risk if you do too much too soon.

Your doctor might diagnose a stress fracture with magnetic resonance imaging (MRI) or another imaging technique. Treatment often involves icing the affected area and plenty of rest. Severe stress fractures may require splinting, casting or surgical insertion of a pin into the bone to promote healing.

Symptoms
If you have a stress fracture, you may experience:

• Pain that increases with activity and decreases with rest
• Pain that occurs earlier in your workout in each successive workout
• Pain that increases over time
• Pain that persists even at rest
• Swelling
• A spot that feels tender or painful to the touch

At first, stress fractures may be barely noticeable. But pay attention to the pain. Proper self-care and treatment can keep the stress fracture from worsening.

Causes
Stress fractures are caused by the repetitive application of force. Two types of stress fractures are possible:

• Fatigue fractures - If a normal bone is subjected to overuse or repetitive stress beyond its ability to repair itself, it may crack. This is known as a fatigue fracture. These fractures often occur during high-impact activities, such as running and jumping, but they can occur as a result of prolonged activities such as hiking or walking.
• Insufficiency fractures - When a weak bone, such as one deficient in minerals or weakened by osteoporosis, cracks under the stress of routine activity, it's known as an insufficiency fracture.

Most stress fractures occur in the weight-bearing bones of the lower leg and foot, particularly the bones that run from the midfoot to the toes (metatarsal bones) and the large bone in the front of the lower leg (tibia).

Risk factors
You may be at increased risk of stress fractures if you:

• are an athlete who participates in high-impact sports, such as track and field, basketball, tennis or gymnastics
• are a female athlete with abnormal or absent periods
• suddenly shift from a sedentary lifestyle to an active training regimen, such as a military recruit subjected to intense marching exercises or rapidly increase your exercise length and intensity
• have flat feet or high, rigid arches
• have osteoporosis or other conditions that lead to weakened bones or decreased bone density

Adolescents whose bones haven't yet fully hardened may be susceptible to stress fractures.