Symptomatology.—­In unilateral gonitis weight is not borne by the affected member.  There is noticeable distension of the joint capsule—­a characteristic pendant pouching protrusion.  When both stifles are affected the subject frequently shifts the weight from one limb to the other.  Lameness comes on gradually and during the incipient stages may be intermittent but it progressively increases so that in time affected animals become useless.  In bilateral affections animals drag the toes because of the pain incident to flexing the stifles.  This is particularly evident when the subject is made to trot.  As the disease progresses, atrophy of the quadriceps femoris muscles becomes pronounced and as destructive changes involving the articular cartilages take place.  The subject becomes more lame and eventually is rendered incapable of service.

Upon manipulation of the patellar region, one is impressed with the fact that hyperesthesia does not exist in proportion to the pain manifested during locomotion.  In some cases a gelatinous swelling is present and may be detected by palpating between the straight ligaments of the patella.  Williams, Hughes, Merillat, Hadley and others have directed attention to the existence of floating masses (corpora oryzoidea) in the synovial capsule of this joint in gonitis, and as with all cases of arthritis, irreparable damage is often done the articular cartilages during the course of the ailment.

[Illustration:  Fig. 50—­Chronic gonitis.  The knuckling which results from long continued inactivity of the crural muscles in chronic cases is marked in this instance.  Photo by Dr. L.A.  Merillat.]

Treatment.—­No effective method is as yet known which will control this condition during its incipiency.  The disease progresses, and more or less damage is done the affected parts in the course of months or even years in some cases before subjects are rendered hopelessly crippled.  When recognized early (before chronic gonitis exists) aspiration of the synovia and the injection of diluted tincture of iodin might prove beneficial in cases of synovial distension.  Chronic gonitis is considered an incurable affection and as soon as subjects manifest evidence of distress from this condition they should by all means be taken from work.  Firing and vesication have not been productive of beneficial results.

[Illustration:  Fig. 51—­Gonitis.  Showing position assumed in such cases because of pain occasioned.  Photo by Dr. C.A.  McKillip.]

Open Stifle Joint.

Anatomy of the Joint Capsule.—­This joint capsule is thin and very capacious.  On the patella it is attached around the margin of the articular surface, but on the femur the line of attachment is at a varying distance from the articular surface.  On the medial side it is an inch or more from the articular cartilage; on the lateral side and above, about half an inch.  It pouches upward under the quadriceps femoris for a distance of two or three