Your bones have several functions. They give your body its overall structure and provide support and protection for your internal organs. They store calcium and other minerals and work with your muscles to allow your body to move. They also contain bone marrow, which is where your blood cells are produced.
Although from the outside your bones look like simple, solid structures, they actually have a clever design that allows your skeleton to be strong without being heavy. Each bone is made up of two types of bone tissue:
- a thick outer shell called ‘cortical’ bone
- a strong mesh or scaffolding (like a honeycomb) inside the shell called ‘trabecular’ bone.
Both types of bone tissue are fed by a nerve and blood supply while fat and bone marrow (for blood cell production) fill the spaces. Somebones, such as the ends of the long bones inyour arms and legs, and your spinal bones, havea high proportion of trabecular bone.
Bone tissue is made up of protein hardened by calcium salts and other minerals to make it strong. Bone tissue is alive and constantly changes through life to make sure it remains as healthy as possible. Throughout each bone, older, worn-out bone tissue is broken down by specialist cells called osteoclasts and rebuilt by bone-building cells called osteoblasts. This process of renewal is called bone remodelling. In younger adults, up until about the age of 35 years, there is usually a balance between the amount of bone that is removed and the amount of bone that is laid down; repair and renewal are usually in balance and the total amount of bone tissue thus stays the same.
In childhood, osteoblasts work faster, enabling the skeleton to increase in size, density and strength. During this period of rapid bone growth it takes the skeleton just two years to completely renew itself. In adults, this process takes seven to ten years. Bones stop growing in length between the ages of 16 and 18 years but the total amount of bone tissue you have (the thickness of the cortical shell and the trabecular bone inside) continues to increase slowly until your late twenties.
Bones and osteoporosis
After the age of about 35 years, the difference between the amount of bone that is removed and the amount of bone that is laid down starts to get slightly out of balance as part of the ageing process. As a result, the total amount of bone tissue starts to decrease. This is often described as ‘bone loss’ or ‘bone thinning’. It doesn’t mean your bones look any different from the outside. However, inside, the cortical ‘shell’ thins and the struts that make up the inner structure become thinner and sometimes break down. This results in the holes in the honeycomb structure becoming larger – hence the description ‘osteoporosis’, literally meaning ‘porous bone’. This change in the quality of your bones is much more likely and more significant as you move into later life, which explains why bones become more fragile and fractures become more common in old age.
There are many other factors that can upset this balance of ‘bone remodelling’ and lead to osteoporosis, and these are described here
Who is affected by osteoporosis?
Women and osteoporosis
Women are more susceptible to osteoporosis because bone loss becomes more rapid for several years after the menopause, when sex hormone levels decrease. In addition, women tend to have smaller bones than men and in general live longer, with loss of bone tissue continuing for longer, making fragility fractures more likely.
Men and osteoporosis
Osteoporosis is not a condition that just affects women, although this is a common misconception. If you are a man, you might be thinking osteoporosis can’t affect you as it’s a ‘women’s problem’, but, in fact, one in five men break a bone after the age of 50 years because of low bone strength. Men with osteoporosis tell us that this confusion can sometimes make it more difficult to come to terms with the condition and to seek help and support.
Younger men and women and osteoporosis
Younger men and women (before the menopause) can also, but more unusually, have osteoporosis and fractures. Usually an underlying condition or reason is identified but sometimes no cause is found. The medical word for this is ’idiopathic’. If you are a healthy younger person who is frequently breaking bones, this can be particularly distressing. Diagnosing and treating osteoporosis in men and in younger women and children is complex and generally a referral to a hospital specialist is recommended. For more information see the Scans and Tests Page
Consequences of osteoporosis
Although sufficient force (e.g., when moving at speed or falling from a height) will cause anyone to break a bone, if you have osteoporosis, broken bones are more likely to occur after even a simple fall.
If you are told you have ‘established’ osteoporosis, this means you are someone who has been diagnosed with osteoporosis on a scan and you also have fractures caused by osteoporosis. Bones affected by osteoporosis are not in themselves painful but the broken bones that may result can cause pain and other problems.
A broken wrist can be the first indication that you have osteoporosis. Wrist fractures in women often occur soon after the menopause and typically occur following a fall, as people commonly put out an arm in an attempt to break their fall. Healthy bones should be able to withstand a simple fall so a broken bone in these circumstances, without any other disease, is an indication that there may be underlying osteoporosis.
Fractures that occur because of reduced bone strength are described as ‘fragility fractures’ and many of these will be caused by osteoporosis.
The most common site for a hip to break is across the top of the thigh bone (fractured neck of femur). If you have broken your hip as a result of osteoporosis, you are most likely to be in your late seventies or eighties, although you may be younger. This type of hip fracture typically occurs as the result of a fall. Like any fracture, a broken hip is painful and has an immediate impact on day-to-day living. Most people who break a hip are admitted to hospital and require an operation. If you are fit and well before your hip breaks, you should be able to look forward to independent living with appropriate physiotherapy and help from social services if you need it. As you get older, you may also be coping with other medical conditions, and making an uncomplicated recovery from an operation to mend your hip and getting back to your own home may be less easy. This is why it’s so important to try to do everything possible to prevent a hip fracture happening in the first place. For more information For more information see the Scans and Tests page
Fractures due to osteoporosis of the bones in the spine (vertebrae) usually occur in the lumbar (lower) or thoracic (middle) areas of the spine. They are often referred to as spinal or vertebral fractures. Bones become squashed or compressed because of their reduced strength. Sometimes they are referred to as ‘crush’, ‘collapsed’ or ‘wedge’ fractures, depending on which part of the vertebra is affected. ‘Compression fracture’ is a good way of describing these fractures. Back pain is the most frequent symptom of a spinal fracture; however, the degree of pain varies in different people, with many having no symptoms at all. Why this is so is not clear. In most people, spinal fractures heal over a period of 6–12 weeks and back pain if present tends to decrease during this time. However pain may persist for a longer period, particularly if you have had more than one fracture. For more information see our Living with Osteoporosis page
If you ‘break your back’ does it mean you will be paralysed?
No. The vast majority of fractures that occur in people with osteoporosis following minor levels of trauma are ‘stable’ and do not interfere with the spinal cord or result in paralysis or loss of sensation, except in very unusual cases.
How does osteoporosis cause height loss and spinal curvature (‘dowager’s hump’)?
Although spinal bones heal, they do not return to their original shape, and this may result in height loss and spinal curvature. If fractures in your spine have healed in a flattened or wedge shape, this can cause the spine to tip forwards, resulting in an outward curve (kyphosis) in your back, and height loss. Sometimes these changes can result in a lack of space for your internal organs so other problems such as breathlessness, a protruding abdomen, indigestion or stress incontinence, can occur. Changes in posture due to osteoporosis can affect how you feel about how you look (your body image). If you feel distressed and frustrated by the changes in your body shape and especially if buying suitable clothes has become difficult, our booklet on Clothing and body image may be helpful.
If you are someone with very fragile bones, a fracture of one or more of the spinal bones can occasionally occur after an awkward movement such as reaching up to a cupboard. Unlike hip fractures, which happen when you fall, spinalfractures can occur following everyday activities of daily living such as bending or stooping. This understandably can make you feel very frightened of further fractures and finding ways to continue normal activities with confidence will be important. It is vital to remember that not everyone has fractures that cause symptoms and disability. And, if you do experience such debilitating fractures, there are many things that can be done to help. For more information see our Living with Osteoporosis page
Other bones such as the humerus (upper arm), ribs or pelvis may break if they are fragile but the wrist, spinal bones and hip are the most common places for fractures to occur.
I have heard you can die from osteoporosis, which has frightened me. Can you explain?
Osteoporosis does not itself result in an increased risk of dying. As explained, the changes that occur within the bones to make them less strong, give you no symptoms at all, and fractures in themselves are not fatal. However, breaking bones, especially your hip when you are much older, can result in you becoming more frail and less well and you may find it much harder to get back to the same level of fitness and independence you had before. Statistically, this reduces your life expectancy compared to someone who hasn’t broken their hip. It isn’t the fracture itself but being less well following the fracture, coupled with the many other medical conditions that older people have to cope with, as well as having to have an operation, that can result in reduced life expectancy. Keeping fit and active into old age, as well as good treatment in hospital and after you are discharged, will greatly reduce the chance offractures affecting your life span.
There are a number of less common types of osteoporosis and related conditions, these are outlined on the Rare Types page.