side of the joint. Most mobile joints have
at least one bursanearby, which cush-
ions a pressure point.
There are several types of mobile
joint. The hinge joint is the simplest,
allowing bending and straightening, as
in the fingers. The knee and elbow joints
are modified hinge joints that allow
some rotation as well. Pivot joints, such
as the joint between the 1st and 2nd
vertebrae (see vertebra), allow rotation
only. Ellipsoidal joints, such as the wrist,
allow all types of movement except piv-
otal. Ball-and-socket joints include the
hip and shoulder joints. These allow the
widest range of movement (backwards
or forwards, sideways, and rotation).
Common joint injuries include sprains,
damage to the cartilage, torn ligaments,
and tearing of the joint capsule. Joint
dislocationis usually caused by injury
but is occasionally congenital. A less
severe injury may cause subluxation
(partial dislocation). Rarely, the bone
ends are fractured, which may cause
bleeding into the joint (haemarthrosis)
or effusion(build-up of fluid in a joint)
due to synovitis(inflammation of the
joint lining). Joints are commonly affec-
ted by arthritis. Bursitismay occur as a
result of local irritation or strain.
joint replacementSee arthroplasty.
jouleThe international unit of energy,
work, and heat. Approximately 4,200
joules (symbol J) or 4.2 kilojoules (kJ)
equal 1 kilocalorie (kcal); 1 kJ is equal to
about 0.24 kcal. (See also calorie.)
jugular veinOne of 3 veins on each
side of the neck that return deoxygen-
ated blood from the head to the heart.
The internal jugular, the largest of the 3
(internal, external, and anterior), arises
at the base of the skull, travels down
the neck alongside the carotid arteries,
and passes behind the clavicle, where it
joins the subclavian vein (the large vein
that drains blood from the arms).
Jungian theoryIdeas put forward by
the Swiss psychiatrist Carl Gustav Jung
(1875–1961). Jung theorized that certain
ideas (called archetypes) inherited from
experiences in a person’s distant past
were present in his or her unconscious
and controlled the way he or she viewed
the world. Jung called these sharedideas the “collective unconscious”. He
believed that each individual also had a
“personal unconscious”, containing ex-
periences from his or her life, but he
regarded the collective unconscious as
superior. Therapy was aimed at putting
people in touch with this source of
ideas, particularly through dream inter-
pretation. Jung’s approach was also
based on his theory of personality,
which postulated 2 basic types: the
extrovert and the introvert. One of these
types dominates a person’s conscious-
ness and the other must be brought
into consciousness and reconciled with
its opposite for the person to become a
whole individual.
juvenile arthritisSee juvenile chronic
arthritis.
juvenile chronic arthritisA rare form
of arthritisaffecting children. Juvenile
chronic arthritis occurs more often in
girls, and usually develops between 2
and 4 years of age or around puberty.
There are 3 main types. Still’s disease
(systemic onset juvenile arthritis) starts
with fever, rash, enlarged lymph nodes,
abdominal pain, and weight loss. These
symptoms last for a period of several
weeks. Joint pain, swelling, and stiffness
may develop after several months. Poly-
articular juvenile arthritis causes pain,
swelling, and stiffness in many joints.
Pauciarticular juvenile arthritis affects 4
joints or fewer.
Possible complications include short
stature, anaemia, pleurisy, pericarditis,
and enlargement of the liverand spleen.
Uveitismay develop, which, if untreated,
may damage vision. Rarely, amyloidosis
may occur or kidney failure may develop.
Diagnosis is based on the symptoms,
together with the results of X-raysand
blood tests, and is only made if the con-
dition lasts for longer than 3 months.
Treatment may include antirheumatic
drugs, corticosteroid drugs, nonsteroidal
anti-inflammatory drugs, or aspirin.
Splints may be worn to rest inflamed
joints and to reduce the risk of deformi-
ties. Physiotherapyreduces the risk of
muscle wasting and deformities.
The arthritis usually clears up after sev-
eral years. However, in some children, the
condition remains active into adult life.JOINT REPLACEMENT JUVENILE CHRONIC ARTHRITISJ