ounding tissues.

The most prominent _clinical features_ are swelling and discoloration.
The swelling, especially in superficially placed joints, is an early
and marked symptom, and is mainly due to the effusion of blood into
the joint (_haemarthrosis_). In deeply placed joints, discoloration may
not appear on the surface for some days, especially if the violence
has been indirect. The joint is kept in the flexed position, and is
painful only when moved. In haemophilic subjects, considerable effusion
of blood into a joint may follow the most trivial injury.

A slight degree of serous effusion into the joint (_hydrarthrosis_)
often persists for some time, and tuberculous affections of joints not
infrequently date from a contusion.

The _treatment_ is the same as for sprains (p. 36).

#Wounds of Joints.#--The importance of accidental wounds of
joints--such, for example, as result from a stab with a penknife or
the spike of a railing--lies in the fact that they are liable to be
followed by infection of the synovial cavity. The infection may
involve only the synovial layer (_septic synovitis_), or may spread to
all the elements of the joint (_septic arthritis_). These conditions
are described with diseases of joints.

Penetration of the joint may sometimes be recognised by the escape of
synovia from the wound, or the synovial layer or articular cartilage
may be exposed. When doubt exists, the wound should be enlarged. The
use of the probe is to be avoided, on account of the risk of carrying
infective material from the track of the wound into the joint.

Penetrating wounds of joints are treated on the same lines as compound
fractures. If the penetrating instrument is to be regarded as
infected,--as, for example, when the spoke of a motor bicycle is
driven through the upper pouch of the knee,--the injury is to be
looked upon as serious and capable of endangering the function of the
joint, loss of the limb, or even life itself. Reliance is chiefly laid
on primary excision of the edges and track of the wound, and other
measures employed in the treatment of gun-shot wounds. While the wound
in the synovialis and capsule is sutured, that in the soft parts is
left open. If drainage is employed, the tube extends down to the
opening in the synovialis, but not into the joint itself. If sepsis
supervenes, the joint is opened and irrigated by Carrel's method. Some
form of splint and a Bier's bandage are valuable adjuncts. The fina