| Burden of Disease | Current
Bone & Joint Disease
The principal functions of the skeleton
are mechanical support, maintenance of normal calcium levels (homeostasis)
and creation of red blood cells (haematopoiesis) in the bone marrow. Bones
are extremely dense connective tissues that make up the skeleton. Although
one of the hardest structures in the body, bone maintains a degree of
elasticity owing to its structure and composition. The principal cells
in bone are the osteoclasts and osteoblasts. Osteoclasts are the cells
responsible for the normal breakdown of bone (resorption), while osteoblasts
are responsible for bone formation. Bone is continually undergoing renewal
called remodelling. Most bone turnover occurs on bone surfaces, with the
rate of remodelling differing dependent on locations according to physical
loading, proximity to a joint or the presence of a suitable blood supply.
In the normal adult skeleton, new bone laid down by osteoblasts exactly
matches osteoclastic bone resorption.
structure and composition can be disturbed in a variety of conditions
encompassed by the general term, metabolic bone disease. Osteoporosis
is the most common metabolic bone disease. Osteoporosis is characterized
by an imbalance in remodelling - a relative increase in resorption
that is not matched by a concomitant increase in formation. The bone
matrix is normally mineralized but there is simply less bone. This
contributes to markedly decreased bone strength and leads to an increased
risk of fracture, especially in the spine and hip.
Osteoporosis means skeletal fragility. Hip fractures
are the most important type of osteoporotic fracture, both in terms
of direct health costs and social effects on the patient. Osteoporosis
is already an important public health problem in all developed countries
and is becoming one in most developing countries.
Arthritis is one of the most common medical problems in the world
and the number one cause of disability in the USA. The word arthritis
is a blend of the Greek words “arthron” for joint and “itis”,
for inflammation, literally meaning “joint inflammation”.
Rheumatoid arthritis (RA) affects around 0.5-3% of the population, but
more frequently in women. RA is an inflammatory condition, whose exact
cause is unknown. It is believed however to be caused by the body’s
immune system attacking the tissue that lines the joints.
RA is multifactorial in origin (genetic, hormonal, environmental and other
factors), with contributing factors including hormones, race, diet, trauma,
and ‘triggering agents’ (most likely bacteria or virus). Climatic
conditions can exacerbate discomfort.
Osteoarthritis (OA) is the most common form of arthritis, affecting around
5-10% of the total population. OA is most common in women and adults over
age 45. It develops when the smooth covering over bones in the joints
(articular cartilage) starts to break down. This can occur as a result
of trauma, aging or failure of joint repair and maintenance mechanisms.
Degradation of the cartilage can be associated with underlying bone damage,
thickening and bone-on-bone friction.
There is no single cause for OA, with identified risk factors including:
being overweight, advancing age, low socio-economic status, hereditary
factors, chronic stress across joints or joint trauma (such as in sports
injuries) and other metabolic or inflammatory disorders.