What is Osteoporosis

Osteoporosis is a condition in which bones lose their strength and are more likely to break, usually following a minor bump or fall. Broken bones are also referred to as ‘fractures’ (the words mean the same thing). Fractures that occur because of reduced bone strength are described as ‘fragility fractures’ and many of these will be caused by osteoporosis. One in two women and one in five men over the age of 50 experience fractures, mostly as a result of low bone strength. Although fragility fractures caused by osteoporosis can happen in various parts of the body, the wrists, hips and spine are the most commonly affected sites.

Osteoporosis is also a term used to describe low bone density as measured on a bone density (DXA) scan. This means your bones may have lost strength.

For more information see our Scans page

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. 

Your Bones

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. Some bones, such as the ends of the long bones in your arms and legs, and your spinal bones, have a high proportion of trabecular bone.

Scientic bone imageBone 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 & 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 in our Are you at risk page.

Are you at Risk?