IN 1938, while on Dr. Arthur Krida's Orthopedic Service at Bellevue Hospital, I removed a cyst of the medial meniscus. It was observed at that time that the hemispherical cystic mass disappeared into the knee joint on acute flexion and reappeared on extension of the knee, reaching its maximum dimensions at a point 25 to 30 degrees short of complete extension.
In 1943 I presented before the Canal Zone's Isthmian Medical Society a series of twelve cysts of the knee cartilages, both internal and external. The pathognomonic "disappearing sign" was described as a common finding in each of the patients operated on by Lieutenant Colonel Marcus Schwartz and me.
During the past three years eighteen more cysts of the medial and lateral menisci have been diagnosed and fifteen of them excised. In each of this last series the physical sign was present, viz., disappearance on acute flexion and reappearance on