May also be called: Joint Swelling; Swollen Joints
Joint effusion (ih-FYOO-zuhn) is swelling in a joint
due to fluid moving into the soft tissues surrounding the joint.
More to Know
The body makes many different fluids, including blood,
lymph (part of the body's immune
system), and synovial fluid, which helps lubricate joints. Effusion is swelling
that happens when fluid leaks out of a vein, artery, lymph vessel, or synovial membrane
into the surrounding tissue. This causes the tissue to expand, or swell.
When effusion happens in a joint — commonly the knee — excess fluid
can pool in a part of the joint called the synovial cavity. It then leaks out into
the soft tissue around the joint. This can happen as a result of injury, infection,
Injuries to joints can rupture blood vessels or lymph vessels,
causing blood or lymph to build up under the skin. Effusion following an injury can
sometimes be a sign of a broken bone or a tear in a ligament or tendon. Joint effusion
caused by an injury often is accompanied by joint pain.
In effusions due to infection, germs
(bacteria, viruses, or fungi) move from an injury into the bloodstream. When
they reach a joint, they can escape to the bloodstream and cause pain, fever, redness,
Effusion caused by arthritis can happen in autoimmune diseases
such as juvenile idiopathic
arthritis where general inflammation in the body also affects the joints and can
cause both redness and warmth.
Joint effusions also can happen in diseases such as gout, where crystals deposit
in the joint, or in cancerous and noncancerous tumors.
Treatment for joint effusion depends on the cause and often includes resting the
joint and applying ice packs to reduce swelling. In some cases, fluid may be removed
from the joint to reduce swelling and increase the joint's range of motion. This fluid
can be checked for signs of infection, crystals, and other substances to help find
out the cause of the effusion.
Keep in Mind
Effusion is a symptom of an injury or other condition affecting a joint. In almost
all cases, if the underlying condition is identified and treated, the effusion will
go away. Joint effusion that happens for no apparent reason or with a fever should
be checked by a doctor as soon as possible.
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