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 results have attended such heroic corrective measures, nevertheless the occasional serious complications which result from infection likely to be introduced in following such procedures, cause the prudent and skilful practitioner to employ safer methods of treatment.

The application of blistering agents is of no value in stimulating resorption of an excessive amount of synovia in chronic cases and the actual cautery when employed without perforation of the synovial structure, is of little benefit.  Trusses or mechanical appliances for the purpose of maintaining pressure upon the distended parts are of no practical value because of the great difficulty of keeping such contrivances in position.  They usually cause so much discomfort to the subject that they are not tolerated.

A very practical and fairly successful method of treatment consists in the aspiration of a quantity of synovia and injecting tincture of iodin.  Cadiot recommends the drainage of synovia with a suitable trocar and cannula and injecting a mixture consisting of tincture of iodin, one part, to two parts of sterile water, to which is added a small quantity of potassium iodid.  The latter agent is added to prevent precipitation of the iodin.  This authority (Cadiot) further advocates the removal of practically all of the synovia