A hairline fracture happens due to overuse of certain bones. If you play repetitive sports like rowing or bowling in cricket or high impact sports, then your bones might slowly develop a  fine fracture due to the repeated stress.Bones constantly ‘remodel’ and repair themselves through osteoblasts, cells that are responsible for synthesis and mineralization of bone during bone formation and remodeling. When the bones are hurt at a rate that overwhelms the osteoblasts, it leads to damage. 

Common in Athletes 

Almost an epidemic in runners, stress fracture incidence in runners approaches 16% of all injuries. All athletes dread stress fractures, especially those in high impact sports like running. The repeated impact of legs on a hard surface is damaging, and makes them prone to hairlines fractures in the tibia, a weight-bearing bone in the lower leg.

Even if you aren’t an athlete, you can get it too

Even if athletes are likely to suffer from hairline fractures, that doesn’t mean the rest of us are safe. The most common cause of hairline fractures is unexpected exercise.For those who are not used to exercise but start a new regime, this may lead to trouble.

Another cause for worry is for those who have stepped up the intensity of their workout suddenly. Since the muscles are not conditioned to deal with this increased load, it causes muscle fatigue, and the bones are not appropriately supported.There are a number of ‘training errors’ that could cause stress fractures

• Increase in distance of running or frequency of training

• Change in training pattern that is more fatiguing like uphill running

• Decreased surface area over which the load is applied

• Improper running or training techniques

• Poor footwear, especially for runners but a problem for any training

Symptoms are hard to catch

There are several ways that may be used by your doctor to diagnose a hairline fracture. While x-rays are common in diagnosing fractures, MRIs are used in diagnosing hairline fractures, as standard radiographic imaging cannot capture early signs of stress fractures like bony edema.Preliminary tests used will generally be on the lines of the hop test, fulcrum test, or hyperextension test, depending on the area of the fracture.

Immediate treatment

At the time of injury, even if it feels like a sprain or something unimportant, the initial treatment is, to rest the affected area, elevate it, and ice it over the next 24 to 48 hours.An initial painkiller may be of value, provided it doesn’t mask the pain and makes you overuse the area. Doctors may recommend a splint, depending on the area which is affected.

If you want to get better, be lazy!

The recommended treatment for a hairline fracture is simply not to use the area until it has healed. It could take a month to a year or more.The bone will begin repairing itself and finish the work, and you will have your bone back as good as new. Unfortunately, having a stress fracture is well-known to be a danger sign for future hairline fractures.If you cease exercise in the area which was damaged, then by the time it gets better, it will definitely not be in the same state of fit as it was before. While an initial period of complete rest is necessary, usually about two weeks, after that physiotherapy is necessary to get back to normal.Rushing back into exercise too soon will definitely damage the area, so it is recommended that you do this with a proper physiotherapist at hand.

However, it is well known that weight bearing encourages healing as more bone tissue is laid down in the healing area.If weight bearing exercises are done in a controlled manner, it will stimulate healing and leave you in better shape than if you had gone completely without exercise. Weight bearing exercises should be kept gentle

Risk factors for a hairline fracture generally depend on bone health, general health, and exercise habits.

• Factors affecting bone strength such as low bone density lowered bone turnover rate (osteoporosis, osteomalacia).
• Skeletal alignment i.e. leg length differences.
• In women, lower muscular strength and endurance indicate higher risk. There is also a correlation with eating disorders as well as amenorrhea.
• Previous stress fractures.
• Women tend to be at higher risk as they tend to have lower bone density, less lean body mass in the lower limb. A late menarche (after 15 years of age) and previous participation in gymnastics or dance, which are high impact sports, are also predictors in girls.
• In men, prior fractures and increased frequency of seasons of athletics have been correlated with an increased rate of stress fractures, but prior participation in basketball has been associated with a decreased risk.
• Hormonal abnormalities. 

Weight bearing bones, especially in the lower extremities tend to be most affected by hairline fractures. The most common stress fractures occur in the tibia (23.6%) but also develop in the tarsal navicular (17.6%), metatarsals (16.2%), femur (6.6%), and pelvis (1.6%)In layman’s language, Tibia is the shinbone and the larger of the bones extending between knee and ankle. The tarsal navicular is one of the small bones of the foot, important in maintaining the arch. The metatarsals are five long bones between the tarsals and the toes, and the femur is a bone of the upper thigh.All of these are in the legs except the pelvis, showing that the legs are the biggest danger areas.

The first phase of treatment would include rest of the area, along with physical therapy and medication that does not include nonsteroidal anti-inflammatory drugs as that might be counterproductive to your healing.In this phase, weight-bearing is alright but running or any heavy impact exercise isn’t. Other fitness exercises like swimming that would not interfere with recovery are recommended.The second phase of treatment would focus more on professional athletes or other people focused on fitness. The first phase is likely to be complete within a month or six weeks.

The ten per cent rule is very simple. It says, to avoid over training; one should not try for more than a ten per cent increase in ‘load’ per week. A ten percent increase in frequency or distance per week of training will allow your muscles to condition themselves to the training & avoid muscle fatigue. Even after a stress fracture is healed, or during the recovery period, the ten percent rule is an excellent way to look at the maximum increase one should take in the workout routine to condition the body properly.

For some cases, where the area is unlikely to heal on its own (‘nonunion’ between the two fractured portions is likely) surgical intervention might be recovered.There may be one of two types of intervention required. Either the surgery will involve placing a screw to join forcibly the areas, or there may be bone grafting to encourage healing.

There are a few simple steps to reduce your likelihood of getting a hairline fracture while exercising:

1. Begin well: Don’t avoid stretching or warming up exercises. If your muscles aren’t warmed up, you are at high risk for hairline fractures & for injuries in general.
2. Select the right equipment: It may just be selecting your footwear, but getting the right size shoe that is comfortable and made for running is also a way of reducing risk factors for hairline fractures.
3. Don’t overdo it: If you have just started to exercise after a period of rest, don’t start at your previous level. Start at a lower level and work yourself up with the ten percent
4. End properly: Take the time to cool down, and rest your muscles.
5. Lifestyle: With problems like osteoporosis or other issues, it would require a change in lifestyle to reduce risk factors.

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