Cystic degeneration of the lateral meniscus. Pathogenesis and diagnostic approach.

Twelve patients with cystic degeneration of the lateral meniscus were submitted to magnetic resonance and arthroscopy. This study showed that mixoid degeneration is produced initially within the meniscal substance and subsequently progresses towards and may rupture through the outer margin, so producing the clinically detectable cyst on the outer margin of the joint. In the light of the information obtained from magnetic resonance and subsequent surgical verification, existing hypotheses regarding the pathogenesis and evolution of the lesion have been re-examined.