Stress fractures are tiny bone fractures, predominantly found in the weight-bearing bones of the lower limbs, which occur as a result of repetitive forces placed upon the bone that outstrip the bone’s ability to repair itself. They are sometimes known as fatigue, or hairline, fractures.
Bones are living tissue and as such are continually involved in a process of repair and regeneration. Subjecting the bones to stress stimulates them into building new and stronger bone. Weight-bearing exercise, in particular activities and sports that involve running and jumping, cause the bones to be both compressed and twisted. Bones respond to such forces by breaking down old cells and building new bone to strengthen the areas under stress. If the rate of micro traumas to the bone surpasses the rate of bone repair, the tiny cracks, known as stress fractures, will not be able to heal. It is during periods of rest that new bone cells are added, so insufficient recovery time can lead to more severe damage and, eventually, chronic pain.
Various risk factors will increase a person’s vulnerability to developing stress fractures.
Certain inherent risks include:
Other risks include:
- Low bone density
- Misalignment of the lower limb or foot
- A discrepancy in leg length
- Foot structure: either flat feet or high, rigid arches
- Gender: Women are slightly more susceptible, especially young female athletes, who may suffer from what is known as ‘the female athlete triad’, a combination of an eating disorder, irregular menstruation, and osteoporosis.
- Menstrual irregularities
- Overuse: this is the primary cause of stress fractures, and athletes among the people most at risk. Muscle fatigue can contribute to the formation of stress fractures: If the muscles are weakened by overuse, they may be unable to absorb enough shock, which is then transferred to the bones.
- Suddenly increasing the rate or intensity of training. As an example, up to half of the injuries suffered by military recruits are reported to be stress fractures of the long bones in the foot (metatarsals). These injuries are often called ‘March’ fractures as they frequently arise from marching.
- Changing the training surface to one that is harder than usual
- Wearing incorrect footwear that fails to properly support the feet
- Eating a diet that does not include enough calcium, vitamin D, or calories, all of which are critical for building strong bones
- Chronic use of some medications, for example, steroids
Initially, symptoms usually appear as a mild pain that occurs during activity, especially towards the end of a period of training or participation in a sport. There may be some local tenderness, swelling or bruising. Gradually the pain starts earlier and worsens in intensity with each subsequent training session. When the damage has progressed to a certain point, pain persists even when at rest, and night pain becomes common.
The pain might be experienced as a deep ache, made worse with pressure on the affected area, particularly if both sides of the area are pressed at the same time.
Your doctor will make a diagnosis based mainly on your medical history, risk factors, and a physical examination. Questions, relating to the type and level of your sporting activity, diet, and footwear, will help the doctor to assess your individual risk factors. The physical examination might include asking you to perform particular movements in an effort to induce the pain. The structure, alignment, flexibility, and strength of the lower limb will be evaluated.
X-rays might be used for diagnostic purposes, although often stress fractures are too small to be seen, at least until the formation of healing tissues is visible. MRI (magnetic resonance imaging) and CT (computed tomography) scans tend to be of more use. Sometimes a bone scan might be performed, which involves the intravenous injection of a radioactive dye. The radioactive material accumulates in areas of rapid bone changes, and can sometimes show activity at stress fractures, but such scans, although sensitive, are not always very specific.
Rest is the primary treatment for stress fractures. Any activity that causes pain must be avoided in order to allow the bones enough time to heal properly. This period of enforced rest may last from 4-12 weeks, depending on the location and severity of the damage.
During the acute phase, it may be helpful to apply ice to the painful area. The ice should be crushed in a bag and covered with a towel before being applied, and kept on the affected area for as long as is comfortable.
Over-the-counter pain medication such as acetaminophen (Tylenol) or NSAIDs (non-steroidal anti-inflammatory drugs) such as ibuprofen (Advil), naproxen (Aleve) or aspirin can be used, although there is some evidence to show that using NSAIDs may inhibit bone repair.
Your doctor might recommend temporarily using crutches or wearing a brace. In moderate to severe cases a splint or cast, worn for 6-8 weeks, might be necessary.
The return to activity must be undertaken slowly and carefully and at a recommended rate of not more than a 10% increase in intensity per week. Your doctor or physiotherapist may help you by devising a graduated exercise program. Doing too much too soon will delay recovery and increase the risk of damaging your bones again.
Surgery is uncommon for the treatment of stress fractures.
Wearing correctly fitted footwear is extremely important. Shoes should provide proper support and adequate cushioning. Training shoes should be replaced frequently. Orthotic inserts can be very helpful if you have flat feet or high arches.
Ensure that you eat a diet rich in calcium and vitamin D and that provides enough calories for your activity level.
When training, increase the intensity by small increments to reduce the risk of overstressing your muscles and bones.
Alternating running with other activities, for example bicycling or swimming, can help avoid overloading certain muscles and bones.
If you experience any pain or swelling in the foot or lower limb while participating in a particular sport or activity, stop and rest for a few days.