Webster's New World Medical Dictionary

osteochondritis dissecans
A condition in which
a fragment of bone in a joint is deprived of blood and
separates from the rest of the bone, causing soreness
and making the joint give way. Diagnosis is made via
X-ray. Treatment usually involves casting, although if
the fragment has detached completely, arthroscopic
surgery may be necessary. Abbreviated OCD and OD.
osteochondroma
An abnormal, solitary, benign
growth of bone and cartilage, typically at the end of
a long bone. Osteochondromas are usually discov-
ered in persons 15 to 25 years of age and are the
most common benign bone tumor. An osteochon-
droma is typically detected when the area around it
is injured or when it becomes large.
osteochondromatosis
A condition that is char-
acterized by multiple benign tumors of cartilage,
called osteochondromas, projecting from bone,
most often from near the ends of long bones. In a
small proportion of cases, an osteochondroma may
become malignant. Also known as multiple exos-
toses. The condition can be hereditary, in which case
it is called hereditary multiple exostoses (HMS).
osteochondrosis
Any disease that affects the
progress of bone growth by killing bone tissue.
Osteochondrosis is seen only in children and teens
whose bones are still growing.
osteoclasia
Destruction and reabsorption of
bone tissue, as occurs when broken bones heal.
osteoclasis
The surgical destruction of bone tis-
sue. Osteoclasis is performed to reconstruct a bone
that is malformed, often a broken bone that healed
improperly. The bone is broken and then reshaped
with the aid of metal pins, casting, and bracing.
osteoclast
A type of large bone cell that plays a role
in the growth and repair of bones. Osteoclasts may
also appear abnormally. See also 
osteoclastoma.
osteoclastoma
A tumor of bone characterized by
massive destruction of the end (epiphysis) of a long
bone. The site most commonly struck by this tumor
is the knee — the far end of the femur and the near
end of the tibia. The tumor is often coated by new
bony growth and may grow aggressively. It may
cause pain and restricts movement. Treatment is by
surgery. Also known as giant cell tumor of bone.