Etiology and Occurrence.--Wounds of the fetlock region resulting in perforation or destruction of a part of the capsular ligament are caused by all sorts of accidents, such as wire cuts, incised wounds occasioned by plowshares, disc harrows, stalk cutters and other farming implements. In runaways the joint capsule is sometimes punctured by sharp pieces of wood or other objects. In horses driven on unpaved country roads the fetlock is occasionally wounded by being struck against the sharp end of some object, the other end of which is firmly embedded in the ground. In one instance the author treated a case wherein the fetlock joint was perforated by the sickle-guard of a self-binder. In this case there occurred complete perforation causing two openings through the _cul-de-sac_ of the joint. Such wounds are produced by implements which are, to say the least, non-sterile, and this perforation of the uncleansed skin conveys infectious material into the joint capsule. Yet in many instances, especially in country practice, no infectious arthritis results where cases are promptly cared for. Symptomatology.--A difference in the character of symptoms is evidenced when dissimilar causes exist. Small penetrant wounds which infect the synovial membranes cause infectious arthritis in some cases, whereas a wound of sufficient size to produce evacuation of all synovia will, in many instances, cause no serious distress to the subject, even when not treated for several days. If it is not evident that an open joint exists and the articular cavity is not exposed to view a positive diagnosis may be early established by carefully probing the wound. In some cases where a small wound has perforated the joint capsule, swelling and slight change of relation of the overlying tissues may preclude all successful exploratory probing. In such instances it is necessary to await development of symptoms. Twenty-four hours after injury has been inflicted, there is noticeable discharge of synovia which coagulates about the margin of the orifice, where synovial discharge is possible. Particularly evident is this accumulation of coagulated synovia where wounds have been bandaged--there is no mistaking the characteristic straw-colored coagulum which, in such cases, is somewhat tenacious. No difference exists between other symptoms in infectious arthritis caused by punctures, and non-infectious arthritis, excepting the intensity of the pain occasioned, the rise in temperature, circulatory disturbances, etc.; all of which have been previously mentioned.