The jump sign is a jerk produced during the passive movement of the head of the tibia under the femoral condyle.
The jump sign is elicited by the passing of the damaged cartilage between the condyle and the tibia.
The most evident pathology of knees demonstrating this sign is the injury to the posterior half of the internal semilunar cartilage; any other intracapsular lesions are accessory.
Knees showing the jump sign and those in which there is a snapping or clicking, or spring knees, should be definitely differentiated.
Knees presenting the jump sign should always be operated upon and the entire semilunar cartilage removed. If this is not done, relapses and arthritis will follow.
(C) 1935 All Rights Reserved.The Journal of Bone and Joint Surgery, Inc.