bones

Musculoskeletal system

Introduction

The bone and joints are the two parts of the musculoskeletal system most affected by ageing. The older person with musculoskeletal problems may often be in pain and have mobility problems.

Lost bone mass and osteoporosis

Bone is constantly replaced and remodeled throughout life, so that old cells are substituted by healthy new ones and so that the skeleton can adjust to changing stresses (loads). But from about the age of 35, more bone cells wear out than are replaced by new ones. The result is a gradual and progressive loss of bone (or more correctly bone mass) and when this reaches a certain amount it is called osteoporosis. The World Health Organization (WHO) has defined osteoporosis as a bone density 2.5 standard deviations or more below the mean value for young adults. The rate of bone loss increases in women after the menopause.

Loss of bone mass with age in men and women

Osteoporosis simply means "porous bones" and the main effect of the condition is to make trabecular bone (the type found in the vertebrae and at the ends of long bones) wider but more hollow, with holes like a sponge and with a thinner outer wall. The consequence is skeletal fragility and an increased risk of fracture after trauma.

Factors that potentiate osteoporosis

Reduction in body estrogen in women from the menopause onwards.
Age (the older a person is, the more years that bone loss has occurred).
Poor diet with low calcium intake (may be due to anorexia, slimming diets, lack of knowledge about diet).
Inactivity – bone is remodeled in response to changing stresses on it.
Use of high-dose oral corticosteroids for three months or longer.
Smoking, alcohol abuse.
Over-exercise earlier in life so extreme that it led to loss of periods in women.
Family history.

Fractures as complications of osteoporosis

Fractures may occur because of trauma (such as a fall) but sometimes the fractures are painless and have no obvious cause.

Crush fractures in the backbone are common. The bones of the spine collapse into each other, and the person may lose several centimeters in height and develop a curved, hunched back (dowager’s hump, or kyphosis). In extreme cases, the lungs may be compressed, causing respiratory problems.
Falls may lead to wrist (Colle’s) fractures.
Falls may lead to hip (femur) fractures, which are common and costly in terms of both healthcare and quality of life.

Increase in risk of hip fractures with loss of bone mass

Hip replacement

Osteomalacia

Osteomalacia is a condition in which some bone is not properly calcified so that it is soft and weak. It is caused by a lack of, or disturbance to the metabolism of, Vitamin D:

Gastrointestinal problems or kidney failure.
Lack of skin exposure to sunlight e.g. in the house-bound elderly (sunlight is needed to synthesize Vitamin D in the skin).
Poor dietary intake of Vitamin D.
Poor absorption of Vitamin D.
Renal disease.
Some drugs e.g. anticonvulsants.

Bone pain and tenderness and weakness in associated muscles lead to a waddling gait and difficulty getting out of chairs and climbing stairs.

Comparison of normal bone, osteoporosis and osteomalacia

Joints and arthritis

Osteoarthritic joint

Osteoarthritis

In osteoarthritis, the cartilage thins instead of thickening as it normally does in old age. Osteoarthritis may be caused by:

Ageing of connective tissue.
Inherited predisposition.
Abnormal joint.
Biochemical anomalies of cartilage.
Previous inflammatory joint disease.

Osteoarthritis Rheumatoid arthritis

One or two joints affected, especially hips/knees Many joints affected, symmetrical, often hands and feet

Weight-bearing surfaces (cartilage) damaged Inflammation of tissue lining the joints and tendons

The underlying bone reacts by changing shape

The patient does not feel ill Sufferer feels ill and irritable

Osteoarthritis is the most common type of joint disease in older people. Can occur in young and old alike, although the prevalence increases with age; less common in the older person than osteoarthritis. It is more common in women than in men.

Rheumatoid arthritis

Rheumatoid arthritis is an inflammation of the joints. When it arises in old age for the first time it may be very sudden and severe. On the positive side, it may be self-limiting.

Joint with rheumatoid arthritis

Problems of daily living

Musculoskeletal problems are the most common causes of functional limitations and immobility in the elderly. They are widespread, disabling and hard to treat.

Age-related changes in walking upstairs

Osteoarthritis	Rheumatoid arthritis
One or two joints affected, especially hips/knees	Many joints affected, symmetrical, often hands and feet
Weight-bearing surfaces (cartilage) damaged	Inflammation of tissue lining the joints and tendons
The underlying bone reacts by changing shape
The patient does not feel ill	Sufferer feels ill and irritable
Osteoarthritis is the most common type of joint disease in older people.	Can occur in young and old alike, although the prevalence increases with age; less common in the older person than osteoarthritis. It is more common in women than in men.