It would appear to me justifiable to draw the following conclusions from the clinical and experimental investigations on which this paper is founded.

(1) The mechanism of rupture of the semilunar cartilages generally accepted does not explain many of the anatomical and pathological findings.

(2) The mechanism does not fall into the simple scheme of the conventional theory.

(3) Anatomical investigations show the existence of intimate legamentous connections between the cartilages and crucial ligaments.

(4) Clinical observations and experiments made on the cadaver by the writer show that partial or complete tearing of the crucial ligaments often accompanies rupture of the cartilages.

(5) In rotation movements of the knee (in semiflexion) excessive tension on the crucial ligaments is transmitted to the semilunar cartilages, and so may produce a variety of lesions.

(6) Laceration of a meniscus through the intermediation of the crucial ligaments can occur in forward sliding of the tibial condyles or vice versa; also in consequence of excessive lateral sliding of the femur, combined with a rotation movement.

(7) Incomplete lacerations of the crucial ligaments occur more frequently than is generally admitted. In the course of operative exploration of the knee such partial lesions are likely to remain unobserved.