- What are bones made of?
- What keeps bones healthy?
- What is bone injury?
- How do we heal from bone injury?
- How do we prevent bone injury?
1. What are bones made of?
Bone are made of connective tissue reinforced with calcium and specialised bone cells. Just like muscle, bone is a living tissue with its own blood and nerve supply.
Bone has different layers to it, as described below:
Periosteum
This is the hard outer layer, akin to the shell of an egg
Compact bone
This is the layer underneath the periosteum, that gives bone its strength and stiffness
Spongy (cancellous) bone
This layer gives bone its flexibility and shock absorbing capacity
Marrow
This innermost layer is responsible for producing blood cells and is soft
2. What keeps bones healthy?
Bones like to be exercised and have force going through them in order to keep them strong. If they are subjected to appropriate forces and loading, coupled with ample time for recovery after exercise, bone becomes denser and tougher. Bone also needs collagen, calcium and hormones like vitamin D to remain strong.
3. What is bone injury?
Sometimes it is obvious how bone has become injured (e.g., from a fall or trauma), but most of the time, there are many different contributing factors at play. Generally speaking, bones can be injured in one of 3 ways:
Acute fracture
This occurs when a bone is subjected to a sudden or powerful force that is greater than its elasticity. This can be a compressive, twisting or pulling force.
”In engineering terms, elasticity is the ability of a deformable body to resist a distorting effect and to return to its original size and shape when that influence or force is removed.”
This results in one or more of the bone layers deforming and breaking, causing a fracture. If this only occurs in the Periosteum (outer layer), it is called a hairline fracture. Fractures that go through all layers are more significant and often need immobilsation in a boot, cast or even surgery to stabilise the fracture.
Pathological fracture
This is when a bone’s elastic capability has been compromised due to poor bone quality.
The commonest reason for this is low bone density. However, there are many other reasons why bone quality may be adversely effected including metabolic and hormonal issues, medications and tumours. In pathological fractures, low energy forces with an innocuous mechanism can cause injury (e.g., trivial falls or knocks). Pathological fractures often need further investigation and management.
Stress injury and fracture
Stress injury or stress fracture is very common, particularly in people who do lots of high impact activity such as running or other sports.
If bone is continually exposed to repeated forces that are not high enough to cause an acute fracture, but without adequate time for healing and recovery, a stress reaction phenomenon may occur. The bone tries its best to heal rapidly and swells with fluid, a process called bone oedema or stress reaction.
The stress reaction process can be broken down into stages:
Stage 1 – The periosteum (or shell) of the bone becomes swollen and painful. The muscles that attach to the affected bone also become tender, tight and inflamed.
Stage 2 – The bone marrow inner layer becomes swollen.
Stage 3 – The compact and spongy bone layers between begin to swell.
Stage 4 – All the bone layers are now swollen with its integrity breached, and a fracture line develops. The stress reaction has now turned into a stress fracture.
4. How do we heal from bone injury?
Bone is incredibly good at healing itself after an injury. However, this process can take several weeks to months. Remodelling is the process where the old bone tissue is replaced by new healthy tissue.
In order for bone to Remodel, we need to provide our bodies with the optimum environment for healing. This includes:
Optimal loading
Under the appropriate loading conditions, bone injuries are stimulated to heal. Depending on the bone injury type, size and location, it is possible to determine the appropriate level of loading to aid fracture healing. This could range from complete oˇoading (non-weight bearing in a cast or crutches), partial loading (able to put some force through the injury) to full loading (able to put higher forces through the injury often with restrictions).
Diet
Maintaining a high calorie, balanced diet, rich in calcium along with Vitamin D is vital to give the body the energy and resources it needs to heal.
Sleep
Prioritising sleep quality and quantity is key as this is the time where our body does most its healing.
Avoid alcohol and smoking
Both alcohol and smoking significantly delay bone healing. It is best to avoid them completely these whilst you are recovering.
Medical treatments
Some medicines and treatments can aid bone healing in certain circumstances. Your doctor will guide you if this applies to you.
Surgery
Most stress injuries or stress fractures will not require surgery. In some cases, particularly with acute and pathological fractures, bones fragments can be surgically stabilised in order to help them to heal. It is important to remember that the surgical procedure does not itself heal bone, but just provides stability across the fracture site. It is vital to continue to optimise the other above points.
5. How do we prevent bone injury?
It is important to understand why bone has become injured in the first place in order to prevent it from occurring again.
Often, there are many factors that may have contributed to the injury, as summarised in the diagram below.
Overtraining (volume / frequency / type)
This is the most common risk factor for bone injury, particularly stress injuries. When changing your training volume, frequency or exposing your body to new types of training, it is important to allow your bone and soft tissues time to adapt to the change in stimulus. Be mindful of high-risk moments in your exercise plans, such as training for events or competitions. Incorporating rest and low impact days into your training week can be very useful.
Nutritional intake
It is important to ensure we have enough calories on board to allow bone to heal after exercise. If we train for prolonged periods of time in a calorie deficient state, we increase the risk of bone injury significantly. Making sure we have a healthy and balanced diet of macronutrients, as well as calcium and vitamin d is key.
Hormonal and metabolic factors
bone health and turnover is intrinsically linked with our hormonal systems. Hormone profiles differ with age and sex, making certain times of life more high risk for bone injury e. G. , adolescent years, post-menopausal, over 50 years old. Key hormonal and metabolic axes that play an important in bone health include:
- Sex hormones (oestrogen, progesterone and testosterone)
- Stress hormones (adrenaline, cortisol, aldosterone and angiotensin) Thyroid hormone
- Parathyroid hormones
- Iron
Medical factors
Certain medical issues can disrupt bone health and development making injury more likely. It is important to discuss these with your doctor to see if they are relevant.
Biomechanical factors
Our biomechanics can play an important role in how our skeletal system transmits force. It may be worth reviewing your biomechanics, particularly with running and sport, to reduce force transmission and optimise your technique. Optimising biomechanics may involve the following:
Running assessment
Sport specific assessments e.g., golf swing, tennis strokes Equipment e.g., racquet and club style, type Biomechanical adjuncts e.g., footwear, orthotics, braces
Sleep
As described above sleep is key for bone healing and recovery. If we are getting less than 6-7 hours a night, and our sleep is of poor quality, our risk for injury significantly increases. Particularly if we are also very active during the day.
Strength and mass capacity
Bones need strong muscles and soft tissues around them to provide support. By improving the strength of our muscles, we can deflect force transmission away from our bones, leaving them less vulnerable to injury. A good example of this is improving calf strength to prevent shin splints.
Social, performance and financial pressure
We are often unaware of external pressures which may cause us to overtrain or train sub optimally. By mitigating these pressures, we can often train with more balance and purpose. Common examples of this include:
Pressure from social media
- Pressure from friends, family and colleagues (e.g., to play in team games, commitment to social exercise and activity)
- Financial commitments (e.g., professional or semi-pro sportspeople earning through sport)
Poor mental health and wellbeing
Although often overlooked, our mental health is intrinsically related to recovery and healing. Stress, low mood and anxiety can cause internal inflammation within the body and significantly compromise bone health, leave us vulnerable to injury and delay healing. Getting help from a suitably qualified mental health or sports psychology professional is essential when looking after our heath or wellbeing.
