1. Etiology: The cysts are consequent on direct trauma, usually on the outer side of the knee, causing a contusion of the meniscus.
2. Pathology: The cysts are multilocular and are due to progressive mucoid degeneration of the cartilage substance, from the center of which they have been extruded. They are lined with a layer of compressed young fibrous tissue, the end result of the round-cell proliferation around the areas of degeneration.
3. Treatment: Removal of the entire cartilage. Lesser procedures are followed by recurrence.