in that both may occur
simultaneously and as the result of the same cause. Some animals are
undoubtedly predisposed to disease of synovial structures. The average
horse that has been subjected to hard service on pavements or hard roads
at fast work suffers synovial distension of bursae, thecae or of joint
capsules. Some of the well bred types such as the thoroughbred horses
may be subjected to years of hard service and still remain "clean
limbed" and free from all blemishes. Thus it seems that subjects of
rather faulty conformation, animals having lymphatic temperaments and
the coarse-bred types, are prone to synovial disturbances such as
thoroughpin, bog spavin, etc., sometimes having both legs affected.

[Illustration: Fig. 58--Fibrosity of tarsus as a complication in chronic
thoroughpin.]

Symptomatology.--Thoroughpin is characterized by a distended condition
of the tarsal sheath which is manifested by protrusions anterior to the
tendo Achillis. However, where but moderate distension of the sheath
exists, there is little, if any, bulging on the mesial side of the hock
and but a small hemispherical enlargement is presented on the outer side
of the tarsus, anterior to the summit of the os calcis. In some
instances the protruding parts assume large proportions, but always,
because of the relationship between the fibular tarsal bone (calcaneum)
and the tendon sheath, the larger protrusion is situated mesially.

During the acute inflammatory stage there is marked lameness present but
this soon subsides when local antiphlogistic agents are applied to the
parts. In fact, spontaneous relief from lameness usually results in the
course of ten days' time following the appearance of thoroughpin. No
lameness marks the advent of this affection when it develops as the
result of continuous strain and concussion occasioned by hard service,
and local changes tend to remain in _status quo_.

[Illustration: Fig. 59--Another view of same case as illustrated in Fig.
58.]

Treatment.--Rest and the local application of heat or cold will suffice
to promote resolution of acute inflammation and lameness when present
will subside within two weeks. In chronic affections, however, the matter
and manner of effecting a correction of the condition--distended tarsal
sheath--merit careful consideration. While drainage of distended thecae
and bursae by means of openings made with hot irons was practiced by the
Arabs, centuries ago, and good resul