Facts on File Encyclopedia of Health and Medicine

to the head of the humerus (long BONEof the
upper arm), causing PAINand constricting range of
motion. Doctors do not know what causes adhe-
sive capsulitis, commonly called frozen shoulder.
The condition may be primary, in which there are
no contributory conditions, or secondary, in which
other conditions exist that may cause changes that
allow adhesive capsulitis to develop. Adhesive
capsulitis affects women somewhat more fre-
quently than men and typically occurs in people
over age 50.

Symptoms and Diagnostic Path
Adhesive capsulitis begins with acute pain in one
shoulder that occurs for no obvious cause. Within
weeks to months adhesions (scarlike tissue)
develop that progressively limit the affected shoul-
der’s range of motion. Most people first notice
restricted movement when trying to reach up and
behind, such as combing the HAIR, and when try-
ing to reach back and behind, such as for a wallet
in the pocket. The adhesions and range of motion
restrictions progress until the person has very lim-
ited use of the shoulder. In most people the adhe-
sions gradually lessen and the pain subsides over a
period of one to three years. Doctors sometimes
refer to the three stages of adhesive capsulitis as
freezing, frozen, and thawing.
The pattern of symptoms is generally distinctive
enough to allow diagnosis. The doctor may choose
to perform diagnostic imaging procedures such as
X-RAYor MAGNETIC RESONANCE IMAGING(MRI) to rule
out other possible causes of the symptoms.

Treatment Options and Outlook
Because adhesive capsulitis is nearly always self-
limiting, treatment primarily targets pain relief.
Analgesic medications, heat, and PHYSICAL THERAPY
in combination may improve range of motion.
When symptoms are severe and do not respond to
these measures, the doctor may recommend
arthroscopic surgery to release the contractures. In
most people such surgery relieves the pain and
improves range of motion.
The entire course of adhesive capsulitis, treated
nonsurgically, typically spans 1^1 ⁄ 2 to 3 years, after
which about half of people recover completely
with no residual pain or restrictions on range of
motion. In some people range of motion improves

though remains limited. A few people experience

residual pain and contractures that result in long-

term disability.

Risk Factors and Preventive Measures

Conditions that appear to increase the risk for

adhesive capsulitis include HYPERTHYROIDISM(over-

activeTHYROID GLAND), DIABETES, and HYPERLIPIDEMIA

(elevated CHOLESTEROL BLOOD LEVELSand TRIGLYC-

ERIDE BLOOD LEVEL). Adhesive capsulitis is also more

common in people who have SPINAL CORD INJURY,

PARKINSON’S DISEASE, certain forms of NEUROPATHY,

and traumatic injury to the structures of the

shoulder. Despite these correlations, doctors do

not know what initiates the onset of adhesive cap-

sulitis and therefore do not know what measures

may prevent its development.

See also CHRONIC PAIN; COMPLEX REGIONAL PAIN

SYNDROME; SURGERY BENEFIT AND RISK ASSESSMENT.

aging, musculoskeletal changes that occur with

The muscles, connective tissues, and SKELETON

arise from the mesoderm in the EMBRYOat about

two weeks of gestational age. The skeleton’s first

form is as fibrous membranes (the bones of the

cranium) or CARTILAGE. Through a process called

ossification or osteogenesis, cartilage cells (chon-

drocytes) convert to BONEcells (osteoblasts, osteo-

cytes, and osteoclasts). This early ossification uses

the fibrous membrane (called intramembranous

ossification) or the cartilage skeleton (called endo-

chondral ossification) as a mold or template. Bone

cells replace the connective tissue cells to form the

bone matrix.

Areas of specialized bone tissue called second-

ary ossification centers form in the long bones;

these become the epiphyses or growth plates.

After birth the epiphysis extends through the

growth of cartilage, which ossification then

replaces as bone. The process extends through

nearly the first two decades of life. Disorders of

ossification include ACHONDROPLASIA, MARFAN SYN-

DROME, ACROMEGALY, andOSTEOGENESIS IMPERFECTA.

MUSCLE structures gain definition, mass, and

STRENGTHas growth occurs. By four months of age

a healthy infant can support his or her head and

at about six months can sit unsupported and roll

over from front to back or back to front. Between

8 and 12 months, an infant begins to crawl, throw

aging, musculoskeletal changes that occur with 299