Stress fractures and stress related injuries of the bone are common, especially in repetitive sports such as running. 80-90% of stress fractures occur in the lower limb. A stress fracture or stress injury occurs when the load on the bone exceeds the strength of the bone.
There are two important bone cells - osteoclasts and osteoblasts. Osteoclasts are cells that break down bone and osteoblasts make new bone. Osteoclasts respond to load. The higher the load the greater bone breakdown occurs. Osteoblasts respond by building new bone but need energy - calcium, vitamin D and hormones - to meet the demand. When there is a gap between these two cell's activities a bone stress response can happen. This can occur if the load is too great and too much breakdown occurs. Or it can be that there isn't sufficient resources to make new bone. The bigger the gap, the greater the bone damage.
There is a continuum of bone stress responses. This is related to the gap in cellular activity and the length of time there is a gap. Bone stress responses can start as periostitis, where there is inflammation of the bone periosteum. This is the fibrous layer covering the bone. A stress reaction is further down the continuum , where the bone is breaking down and becoming weaker. Stress fractures are the end of the continuum where the bone has been compromised and a partial or complete break has occurred.
80-90% of stress fractures occur in the lower limb and are often related to running. Running is a very repetitive load, with the same structures being loaded each time the foot strikes the ground. The tibia has been reported to be the most commonly affected bone. Different sports lead to different loading patterns and therefore different injury patterns. For example you would rarely see a spinal stress fracture in running, but it is not uncommon in cricket fast bowlers. The same occurs for rib stress fractures in the rowing population.
Stress injuries affect people of all ages who participate in repetitive loading activities. However, female athletes appear to experience more stress fractures than males. Females, especially those with absent or irregular periods, are at a higher risk of stress fractures. Other intrinsic risk factors include:
age - older athletes are at a higher risk
anatomy - high arches and muscle weakness increase the risk
gait - poor running mechanics increase risk
bone - reduced bone density and bone with increases risk
slower runners are at a greater risk due to increased foot contact
nutrition - deficits in certain nutrients as well as calorie deficits will increase risk
a history of previous injury increases your risk.
Extrinsic factors that lead to a higher incidence of stress injuries are:
the type of loading
how much loading
footwear
training or playing surface
The management of a stress fracture relies on a prompt diagnosis and then rest from the aggravating activity. For many injuries, rest is not always best, but in the case of the stress injury it is. If you continue to run for example and this is what caused it, then the bone will continue to deteriorate and a larger, harder to heal problem will develop. You need the bone building cells to catch up.
The goals of the rest period are:
R: removal of the abnormal stress
E: exercise to maintain cardiovascular fitness and prevent atrophy - pain free
S: safe, pain-free return to previous level of activity
T: time for bone maturity to catch up with increasing remodelling.
Whilst you are resting it is important to address the factors that may have lead you to this position. It is important that you progress based on symptoms and physiology rather than a predetermined timeline. As several factors affect the progression of the management. For example the location and the severity of the lesion.
To help prevent stress fractures recurring variety is key. Alternating activities that can accomplish the same goals but load the body and bones in a different way is really helpful. Add some strength training and mobility to further increase the benefits. It is important that you set incremental goals and increase your training loads gradually. Be careful with changes in your training, both the volume and the surface. Also ensure you have a healthy diet and be guided by a dietitian if you need help. Having the appropriate equipment and shoes can make a world of difference. And lastly, check your form. Poor form and biomechanics can lead to certain areas being overloaded. This is where your Sports Physiotherapist can really help.
So the take home messages about stress injuries. Prevent them with variety and gradual build up of training. Treat them with patience and respect of pain.
If you are concerned that you may have a stress fracture, please seek advice from a trained health professional. Our Physiotherapists are able to assess and treat injuries along the stress continuum. Should you have any concerns, please do not hesitate to contact us.
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