Where a vulnerant body penetrates all structures and invades the
interior of the joint capsule the result is that a more or less active
disturbance is incited. The introduction of a sterile instrument into a
joint cavity, under strict asepsis, where a perfect technic is executed,
does not cause perceptible manifestation of the injury, if the opening
so made is small--such as a suitable exploratory trocar makes. But a
puncture made in a similar manner and with the same instrument without
due regard to asepsis is likely to cause an infectious synovitis and
arthritis usually follows.

A larger opening than is produced by means of an exploratory trochar may
be made into a joint cavity, causing escape of synovia as it is secreted
for days and even for weeks and no serious or permanent trouble is
experienced in some cases. If the synovitis or arthritis remains
non-infected and the wound, traumatic or surgical, is not too large,
healing by granulation occurs, and the discharge of synovia ceases.
However, if synovial discharge persists too long because of tardy
closure of an open joint, there is great danger of infection gaining
entrance into the synovial cavity, or in some instances, desiccation of
endothelial cells of the articulation occurs, in areas, and the
reactionary inflammation eventually results in ankylosis.

A small puncture which introduces into the synovial cavity infectious
material of active virulence will cause an arthritis that is more
serious, much more painful and more difficult to handle than is
occasioned by a wound of moderate size, that affords ready escape of
synovia even through the virulence of the infection be the same.

Synovia is a good culture medium and the environment is ideal for