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Have you got a stress fracture?

31-Oct-17

By Karina Teahan, Chartered Physiotherapist

In the first of this two- part series, Karina Teahan, who is a Chartered Physiotherapist and a runner and triathlete, sets out all you need to know about that most niggling of injuries, the stress fracture. In part one she concentrates on diagnosis and in part two she looks at treatment. Read this to help avoid a small injury becoming a big one.

What is a stress fracture / Bone Stress Injury (BSI)?

A bone stress injury (BSI) or stress fracture is the inability of bone to withstand repetitive loading, which results in structural fatigue, localised pain & tenderness” (References 1,2,3 below)

Optimal loading will make our bones stronger – it is a good thing -  and any micro-damage will actually trigger a healing response to create a stronger bone. In technical terms this is skeletal adaptation & increased bone mass. 

However, this optimal loading is time-dependent and if we do too much, or too quickly, too much micro-damage occurs. The net result is a localised reduction in the capacity of the bone to absorb energy and impact and this leads to injury. If untreated this can progress from a stress reaction to a complete bony break. It must be addressed early on.

Who gets BSIs?

Between a third and two-thirds of competitive cross-country and long distance runners have a history of BSI (References 1,2 below). 50% of BSI’s in long distance runners occur in the shin bone with the majority of others occurring in the femur, fibula, heel bone, metatarsals and tarsals.

Generally, long distance runners use a heelstrike-biased pattern. This pattern loads their tibia, fibula and femur more.  Sprinters tend to use a forefoot strike which imparts greater loads on the bones of the foot. (see photos below). That means more tarsal and metatarsal BSIs. This is not an absolute rule. Any runner who overloads their lower limb bones too much can be susceptible to a BSI, depending on their individual running style.

RUNULTRA_Stress-fractures-article-by-Karina-Keahan

Photo credit: Karina Teahan.

Stress fractures are also commonly seen in army recruits, and lots of the studies into stress fractures come from this group.

Risk factors

(References 1,2,3,4,5)

1. Factors modifying the load applied to bone

  • Biomechanical factors: bony misalignment (bow leg or knock knee), poor running mechanics, leg length discrepancy, pes planus (flat foot), pes cavus (excessively high arch).
  • Training factors: 85% of stress fracture athletes can identify a change in their training program prior to their injury. The changes can be in duration and frequency of training sessions, as well as running intensity/speed.
  • Muscle strength & endurance: muscles are protective of bone and when weakened, fatigued or not firing as they should, they cannot reduce the load so well. This means there is increased strain/load on the bone and reduced shock absorption.
  • Training surface & terrain: this is not as straightforward as you may think. It is not just a case of a harder surface being of a higher risk. A very compliant surface, such as sand, may increase energy expenditure and increase muscle fatigue risk factors. Downhill slopes may decrease shock absorption and increase loading. Altered terrain (mountain, trail) may challenge the body and alter the way we usually run/land. Changing from treadmill to hard road may increase bone load/strain. The key is to accommodate to any new running surface gradually.
  • Shoes & inserts: shock absorbing inserts may help and remember to change your runners before they wear out. Some shoe makers suggest doing this after 300-500 running miles.
  • Reduced/inadequate sleep.

2. Factors modifying the ability of bone to resist load

  • Genetics
  • Previous history of a stress fracture.
  • Diet & nutrition. Vitamin D & Calcium are essential for healthy bones and it is suggested that running athletes need more of each than the current RDA of 1000-1300mg Calcium & 600iu Vitamin D (age 14-50 years) so speak to your pharmacist.
  • The incidence of BSI is 1.5-3.5 higher in female athletes.
  • Physical activity history: runners who haven’t had a long history of miles behind them are more likely to get a stress fracture (lack of “chronic workload”), when they suddenly add a large “acute” workload to their bones. Similarly a stress fracture may occur after period of rest due to injury or in the pre-season in other sports.
  • Some medications can negatively influence bones eg glucocorticosteroids & anti-convulsants.
  • Bone disease: osteoporosis & osteopenia.

Diagnosis

A thorough history is the first step in the diagnosis of a BSI. The pain may start as a mild ache that occurs after a specific amount of running but stops once you stop running. The pain will not “go away” as you warm up.

As the bone stress injury worsens, the pain will become more severe and localised, and occur at an earlier stage. It may start to bother you doing normal day-to-day things that involve being on your feet. As it progresses further, you will get night and resting pain. This is because an inflammatory process has begun.

Some bones are easy to examine for tenderness such as the metatarsals, tibia, fibula and you may occasionally see some swelling and redness. The femur and pelvis will be more difficult to examine due to the overlying muscles. The most accurate way to diagnose a stress fracture, along with a good clinical history, is by getting an MRI. A plain x-ray is not sensitive enough to show any changes early on.

A BSI can be classified as low or high risk based on where it is (see table below) (References 1,2) It can be classified as low or high grade dependent on MRI findings. This will be described by your radiologist. (References 1,2)

LOW RISK HIGH RISK
Posteromedial tibia
(inside & back of shin bone)
Femoral neck
especially the tensile (outer) side
Fibula/lateral malleolus
(outside of lower leg)
Anterior cortex of the tibia
(shin bone)
Femoral shaft
(thigh bone)
Talus
(rear foot bone)
Pelvis Navicular
(mid foot bone)
Calcaneus
(heel bone)
Proximal diaphysis of 5th metatarsal
(long bone at outside of foot)

Diaphysis of 2-4th metatarsals
(long bones of foot)

Base of 2nd metatarsal
Great toe sesamoids
(on either side of the junction
between your big toe & 1st metatarsal bone)


Conclusion

BSIs can not be ignored. Treat them as you would a hot spot on your feet during a long run. Take action as soon as you realise what is happening. Don’t just think, “Oh, it will be fine, it is just a niggle.” If it is a BSI, it won’t be fine, it will get worse.

If you take action early, you will save a world of pain later. Read my second article on BSIs. How to treat a stress fracture and get back to running! to help you through.


About the author: Karina Teahan (BSc, MMT, MISCP) is a chartered Physiotherapist and elite runner who graduated from University College Dublin in 2002. She did a Masters at the University of Western Australia and worked in Dublin, Manchester and New Zealand. Karina is now based in a Primary Care Centre in Cork, Ireland.

References:

  1. Warden SJ, Davis IS, Fredericson M. Management and Prevention of Bone Stress Injuries in Long Distance Runners. JOSPT. 2014;44(10):749-765
  2. Behrens SB, Deren ME, Matson A, Fadale P, Monchik KO. Stress Fractures of the Pelvis and legs in Athletes: A Review. Primary Care. Sports Health March April 2013. 5(2): 165-174. DOI:10.1177/1941738112467423
  3. Managing Stress Fractures in Athletes: Rheumatology Network. December 2010
  4. Nattiv A, Loucks A, Manore M, Sanborn F, Sundgot-Borgen J, Warren M. The Female Athlete Triad. ACSM. 2007. DOI: 10.1249/mss.0b013e318149f111
  5. Griffin L, Hannafin J, Indelicato P, Joy E, Kibler W, Lebrun C, Pallay R, Putukian M. Female Athlete Issues for the Team Physician: A Consensus Statement. American College of Sports Medicine. 2003. 1785-1793

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