smaller scale. However, a short bone does not
have a medullary canal or bone marrow. Flat
bones, such as the scapulae (shoulder blades),
sternum (breastbone), and pelvis (hip bones),
serve as attachment surfaces for the large muscles
of movement. They contain a substantial thickness
of compact bone with a thin layer of cancellous
bone in the center. The sternum and the pelvis
also contain bone marrow. Irregular bones, such
as the vertebrae (bones of the spine), carpals
(bones of the wrist), and tarsals (bones of the
ankle), are primarily structures of compact bone
with cancellous bone centers.
Bone Health and Disease
Bones require a steady intake of dietary calcium
and other minerals as well as an adequate amount
of vitamin D, VITAMIN K, and various hormones to
maintain themselves. Deficiencies (and less com-
monly, excesses) of these substances alter bone
structure in ways that can affect bone function.
Though a certain degree of demineralization
occurs naturally as a component of the aging
process, excessive calcium loss results in thin and
weak bones that are particularly vulnerable to
FRACTURE. Fracture is the most common health
condition that affects the bones. Other health con-
ditions involving the bones include OSTEOPOROSIS,
INFECTION (OSTEOMYELITIS), and congenital muscu-
loskeletal anomalies (BIRTH DEFECTS that affect
muscle and bone structure and function).
HEALTH CONDITIONS THAT AFFECT THE BONES
ACHONDROPLASIA arthrogryposis
BONEcancer BONE SPUR
cleft palate FRACTURE
KYPHOSIS LORDOSIS
MARFAN SYNDROME OSGOOD-SCHLATTER DISEASE
OSTEOGENESIS IMPERFECTA OSTEOMALACIA
OSTEOMYELITIS OSTEOPENIA
OSTEOPOROSIS POLYDACTYLY
RHEUMATOID ARTHRITIS SCOLIOSIS
SKELETAL DYSPLASIA SPINA BIFIDA
For further discussion of bone structure and
function, please see the overview section “The
Musculoskeletal System.”
See also AGING, MUSCULOSKELETAL CHANGES THAT
OCCUR WITH; CALCIUM AND BONE HEALTH; CLEFT
PALATE/CLEFT PALATE AND LIP; JOINT; LIGAMENT; MONO-
CYTE; MUSCLE; PHAGOCYTE; SKELETON; TENDON.bone cancer Cancer that occurs in the tissues of
the BONE, either as primary cancer (cancer that
originates in the bone) or metastatic cancer (can-
cer that spreads to the bone from an origin else-
where in the body). Primary bone cancer is rare;
doctors in the United States diagnose about 2,500
people with primary bone cancer each year. Its
three forms are- osteosarcoma, which arises from osteoid (the
formative tissue of new bone) usually in the
upper leg or upper arm in young people ages
10 to 25 - Ewing’s SARCOMA, which results from a TRANSLO-
CATION GENE MUTATIONand generally arises from
the long bones (and occasionally soft tissue
structures) during ADOLESCENCE - chondrosarcoma, which develops in the carti-
lage of the shoulders or pelvis in adults over
age 50
Osteosarcoma accounts for about a third of pri-
mary bone cancers. RADIATION THERAPYfor other
cancers increases the risk for osteosarcoma.
Though primarily a cancer of childhood, osteosar-
coma sometimes occurs in older adults. Oncolo-
gists (cancer specialists) often stage primary bone
cancer only as localized (one contained site) or
metastasized (spread to multiple sites).
The bone is a common site for cancer that
metastasizes from other sites in the body such as
the BREAST, PROSTATE GLAND, and COLON. Metastatic
cancer retains the name of its original site. Multi-
ple myeloma, a cancer of the BLOOD, also affects
bone structure though is not a true bone cancer.Symptoms and Diagnostic Path
The main symptom of bone cancer is PAIN, usually
at the site of the tumor. The pain may be present for
several months before becoming intense enough
for the person to seek treatment, or may develop
suddenly. Sometimes the first indication of bone
cancer is a FRACTURE, either spontaneous (without
trauma) or as a consequence of minor trauma that
would not fracture healthy bone. The diagnostic
path typically begins with X-rays, which can showbone cancer 309