A joint is an area where two or more bones are in contact with each other. Cartilage provides cushioning inside joints (such as in the knee joint), or connects one bone to another (as in cartilaginous joints).
Ligaments join bones to other bones to strengthen joints.
Skeletal muscles run from one bone to another, usually passing at least one joint. They are connected to bones by tendons, which are the long thin ends of the muscles.
What is the function of bones, muscles and joints?
Bones give people shape. They hold the body upright and also protect organs like the heart and the kidneys. They store the minerals calcium and phosphorus, and also contain bone marrow, where new blood cells are made.
There are different types of muscles and joints, each with different functions.
Skeletal muscle is muscle that you can consciously control. When your brain tells a muscle to contract, it shortens, pulling one bone towards another across a joint. Muscles work in pairs – when one shortens, a corresponding muscle lengthens. Physical activity maintains or increases the strength of skeletal muscles.
Smooth muscle sits in and around blood vessels and organs. You can’t consciously control smooth muscle. It helps regulate your blood pressure, airways and digestion.
The heart is made of special muscle called cardiac muscle. You can’t control it consciously. It contracts to make your heart beat.
Joints in the arms and legs are synovial joints – they have fluid in them so bones can move over each other.
Joints in the spine and pelvis are cartilaginous joints – they provide more stability and less movement.
There are also fibrous joints that allow no movement at all – just stability. You have fibrous joints in your skull.
At least half of the age-related changes to muscles, bones and joints are caused by disuse.
Recent studies show that fewer than one in 10 Australians over the age of 50 years do enough exercise to improve or maintain cardiovascular fitness.
Nearly half of all Australians over the age of 75 years have some kind of disability. Common conditions affecting muscles and the skeleton, or the musculoskeletal system, in older people include:
Muscle loses size and strength as we get older, which can contribute to fatigue, weakness and reduced tolerance to exercise. This is caused by a number of factors working in combination, including:
Bone is living tissue. As we age, the structure of bone changes and this results in loss of bone tissue. Low bone mass means bones are weaker and places people at risk of breaks from a sudden bump or fall.
Bones become less dense as we age for a number of reasons, including:
In a joint, bones do not directly contact each other. They are cushioned by cartilage that lines your joints (articular cartilage), synovial membranes around the joint and a lubricating fluid inside your joints (synovial fluid). As you age, joint movement becomes stiffer and less flexible because the amount of lubricating fluid inside your joints decreases and the cartilage becomes thinner. Ligaments also tend to shorten and lose some flexibility, making joints feel stiff.
Many of these age-related changes to joints are caused by lack of exercise. Movement of the joint, and the associated ‘stress’ of movement, helps keep the fluid moving. Being inactive causes the cartilage to shrink and stiffen, reducing joint mobility.
Exercise can prevent many age-related changes to muscles, bones and joints – and reverse these changes as well. It’s never too late to start living an active lifestyle and enjoying the benefits.
Research shows that:
See your doctor before you start any new physical activity program. If you haven’t exercised for a long time, are elderly or have chronic diseases (such as arthritis), your doctor, physiotherapist or exercise physiologist can help tailor an appropriate and safe exercise program for you. If you suffer from osteoporosis, you may also be advised to take more calcium. Sometimes, medications are needed to treat osteoporosis.
Many different conditions and injuries can affect the musculoskeletal system, such as:
They all have different forms of treatment. The best way to prevent illness and injury to the musculoskeletal system is to eat a healthy diet, be as active as you can and keep to a healthy weight.