The anterior cruciate ligament was cut in ten dogs (unilaterally in nine, bilaterally in one). The dogs were killed in two groups, one at seven to nine months and the other at nineteen to twenty-three months.
The dogs were clinically and roentgenographically examined at various intervals. At varying times before death they were given bone-seeking fluorochromes and necropsy was performed in all cases.
Macroscopic, histological, and microroentgenographic examinations revealed proliferative and degenerative changes in the joints in which the anterior cruciate ligament was cut. These changes became increasingly severe for about a year. The osteophytes, which originated periarticularly, took part in remodeling of the condyles. The osteophytcs increased in size for about a year. There was persistent pain as long as marked instability remained. The knees became less unstable in time, apparently by means of an increase in the thickness of the joint capsule. Most of the clinical signs disappeared with decreasing instability. The conclusion was drawn that early stabilization is indicated in cases of rupture of the anterior cruciate ligament.