Bma Illustrated Medical Dictionary

ossificationThe process by which bone

is formed, renewed, and repaired, starting

in the embryo and continuing through-

out life. There are 3 main situations in

which ossification occurs: bone growth,

during which new bone forms at the

epiphyses(ends) of bones; bone renew-

al as part of normal regeneration; and

bone repair following a fracture.

In newborn babies, the diaphysis(shaft)

has begun to ossify and is composed

mainly of bone, while the epiphyses are

made of cartilage that gradually hard-

ens. In children, growth plates produce

new cartilage to lengthen the bones,

and further bone forms at secondary

ossification centres in the epiphyses. By

the age of 18, the shafts, growth plates,

and epiphyses have all ossified and

fused into continuous bone.

osteitisInflammation of bone. The most

common cause is infection (see osteo-

myelitis). Other causes are Paget’s disease

and hyperparathyroidism.

osteitis deformansAn alternative term

for Paget’s disease.

osteo-A prefix denoting a relationship

to bone, as in osteoporosis, a condition

in which the bones thin and weaken.

osteoarthritisA common jointdisease

characterized by degeneration of the

cartilage that lines joints or by formation

of osteophytes, leading to pain, stiff-

ness, and occasionally loss of function.

Osteoarthritis is due to wear and tear on

joints, weight-bearing joints being the

most commonly affected. Weakness and

shrinkage of surrounding muscles may

occur if pain prevents the joint from

being used regularly. Affected joints

become enlarged and distorted by osteo-

phytes.Osteoarthritis occurs in almost

all people over 60, although not all have

symptoms. Factors that lead to its earlier

development include excessive wear of,

or injury to, a joint; congenital deformi-

ty or misalignment of bones in a joint;

obesity; or inflammation from a disease

such as gout. Severe osteoarthritis affects

3 times as many women as men.

There is no cure for osteoarthritis.

Symptoms can be relieved by nonsteroid-

al anti-inflammatory drugs, analgesics,

injections of corticosteroid drugsinto

affected joints, and physiotherapy. In

overweight people, weight loss often

provides relief of symptoms. Surgery for

severe osteoarthritis includesarthro-

plastyand arthrodesis.

osteochondritis dissecansDegenera-

tion of a bonejust under a joint surface,

causing fragments of bone and cartilage

to become separated, which may cause

the joint to lock. The condition common-

ly affects the knee and usually starts in

adolescence. Symptoms include aching

discomfort and intermittent swelling of

the affected joint.

If a fragment has not completely sepa-

rated from the bone, the joint may be

OSTEOCHONDRITIS DISSECANS

O

OSSIFICATION

OSSIFICATION

Blood

vessel

Diaphysis

(shaft) is

already

ossified

Epiphysis

consists of

cartilage

Growth

plate

Marrow

cavity

LONG BONE OF A NEWBORN LONG BONE OF A CHILD LONG BONE OF AN ADULT

Epiphysis

Growth

plate

produces

cartilage

to lengthen

bone

Blood

vessels

form new

branches

to nourish

growing

tissue

Secondary

ossification

centre

Articular

cartilage

protects

end of

bone

Ossified

growth

plate

Marrow

cavity