Stress fractures occur when normal bone is over-trained over a long span, or abnormal bone is stressed too much. As too much stress is put on a bone, microscopic fractures occur, leading to bleeding, inflammation and pain. Repeated such injuries can have a cumulative effect of causing a full bone break.
The tibia (shin) is the most common area for stress fractures (commonly “shin splints” at that locale) but micro-fractures also occur in the femur (upper leg bone), bones of the foot and spine. The injuries are common among athletes, particularly runners and gymnasts. Individuals with abnormal bone quality (osteoporosis), poor eating habits (anorexia) or hormonal disturbances (“female athlete triad”) can be at greater risk for stress fractures.
Symptoms of a stress fracture are limited. It might feel like a general region of pain, tenderness, and pronounced pain with weight-bearing. Pain can flare at the beginning and/or the end of prolonged physical activity, such as a run, and become milder in the interim. As the stress increases or persists, pain might become more acute at a specific spot.
Patients with stress fractures of the hip, for instance, likely would feel pain in the front of the groin while standing and moving. If the pain happens during workouts, it likely would occur earlier in successive workouts. Swelling could result, as well. A stress fracture might keep a patient awake at night or preclude him/her from walking comfortably. Climbing stairs may be too painful for such patients. Ultimately a stress fracture could lead to a complete break of a bone.
A stress fracture is very likely to stem from one or two episodes of dramatic overstressing of a bone's load capacity, or from long-term overtraining – increasing a bone’s load repeatedly but to a lesser extent.
Choice of physical activity is the greatest risk factor for developing stress fractures; the greater the potential impact and demand on bones’ load capacities, the greater the likelihood for stress fractures. A stress fracture is very likely to stem from one or two episodes of dramatic overstressing of a bone's load capacity, or from long-term overtraining.
Physicians look for internal and external factors that can contribute to stress fractures. Internal factors include bone structure, how legs are aligned, flexibility and strength in specific muscles. For example, runners tend to be stronger in hamstring and quadriceps muscles, weaker in adductors. Strength and flexibility deficits can lead athletes to develop stress fractures.
External factors include shoe quality, training regimen and terrain. Terrain makes a difference: Grass or rubber-based athletic tracks are gentler than pavement. Hills put more stress on bones. When training, increases to running time or distance should be gradual – limited to 10 percent – not abrupt.
Runners should have two pairs of running shoes and rotate their use so one pair can better regain its sponginess between runs. After about 400 miles, a pair of shoes should be retired.
A balanced diet and sufficient hydration is important not only to bone composition in younger years but to regular participation in athletics and to recovery from injuries.
The location of pain can dictate what diagnostic instrument is used. Often X-rays do not reveal micro-fractures initially but may, several weeks later, show evidence of a bone healing, suggesting the presence of micro-fractures.
Physicians more often rely on bone scans and magnetic resonance imaging (MRI) tools. With a bone scan, dye is injected into a blood vessel and observed at the point where the bone is replacing itself. This can show evidence of a stress fracture. An MRI allows the physician to observe not only bone swelling but also whether surrounding muscle tissue is involved. Sometimes a computed tomography (CT) scan can help point out micro-fractures’ existence; physicians might be more likely to use this with spinal injuries.
Patients with suspected biomechanical problems would be observed while standing to discern whether their feet pronate (roll inward) or supinate (roll outward, to the side). Specific muscles could be tested to discern strength, stability and flexibility. Patients are put on a treadmill, with the physician observing their gait and stride.
Without a reduction in activity, a stress fracture can lead to a complete bone break and, in the long term, to arthritis.
Reducing participation in painful activities is the most important step that a patient can take. These actions also can help:
- Ice to reduce inflammation.
- Vigilantly monitor pain levels and associated activities.
- Replace outdated equipment, such as running shoes. Wearing shoes with thick soles helps absorb shock and load to the hip joint. Add orthotic insoles to shoes, if needed.
- If biomechanical issues are contributing to pain, learning proper mechanics.
- Strengthen muscles around the injured bone and adequately stretch – particularly after exercise (yoga might be beneficial).
If the patient is an athlete resuming training, the initial duration and distance of training should be reduced to half that of pre-injury levels.