Medial meniscectomy and the creation of "bucket-handle" lesions of the medial meniscus induce mild to moderate osteoarthrotic changes in the knee joints of mature rabbits. The osteoarthrotic lesions studied by gross inspection and histological sections, almost exclusively involve the medial tibial articular cartilage. The pathologic changes begin superficially, pass to the deeper layers, and are characterized by a loss of the glistening of the cartilage surface, peripheral osteophytes, structural irregularities of the matrix, peripheral cloning, hypocellularity, and diminished amounts of glycosaminoglycan. Osteoarthrosis was assessed from 2 to 16 months following surgery using a grading system from 0 (normal) to 15 (severe degeneration). The mean grades at the various time periods studied range from 3.5 to 7. The mild to moderate nature of the osteoarthrosis is shown by the development of the abnormalities without rapid progression to the severely destroyed joints which characterize many other models.