in the body. It usually communicates with the medial sac of
the femerotibial joint cavity by a slit-like opening situated at the
lowest part of the medial ridge of the trochlea. A similar, usually
smaller, communication with the lateral sac of the femerotibial capsule
is often found at the lowest part of the lateral ridge. (Sisson's
Anatomy.)

Thus it is seen that because of its frequent communication with the
other parts of this large synovial membrane, a wound which opens the
external portion of the femerotibial capsule may be the cause of
contamination and resultant infectious arthritis of the whole stifle
joint. Because of the distance between the most dependent part of the
femerotibial articulation and the summit of the patella, one may
misjudge the exact location of the lowermost part of this portion of the
capsular ligament of the stifle joint and thereby fail at once to
appreciate the seriousness of calk wounds in this region.

Etiology and Occurrence.--Wounds to the patellar region are of rather
frequent occurrence, and because of the comparatively unprotected
position of these structures, the capsular ligaments of the stifle joint
may be perforated as a result of violence in some form. Calk wounds
which penetrate the tissues in the immediate region of the lower portion
of the external part of the femerotibial capsule sometimes result in
open joint because of tissue necrosis resulting from the introduction of
infection. Contused wounds sometimes destroy the skin and fascia over
large areas on the lateral patellar region and because of subsequent
sloughing of tissue due to infection as well as to the manner in which
such wounds are inflicted, septic arthritis subsequently occurs.
Penetrant wounds, such as may be caused by a fork tine may not result in
infection; if infectious material is introduced an infectious arthritis
does not necessarily follow, though such cases should be considered as
serious from the outset.

Symptomatology.--The pathognomonic symptom of open stifle joint is the
profuse escape of synovia, indicating perforation of the synovial
capsule; by means of a probe the wound may be explored in a way that
will clearly reveal the nature of the injury.

After a few days have elapsed in cases where considerable infection has
taken place, there is manifestation of pain as in all cases of infective
arthritis. Hughes[48] gives an excellent description of the clinical
aspect of arthritis which applies