It is common for dogs with cranial cruciate ligament damage to also have injury to the mensicus. Simply put, the meniscus is a secondary structure in the knee that helps to provide lubrication for the joint, while also functioning in shock absorption and weight bearing. The menisci (plural for meniscus) are pads between the bones of the joint that function in stability, load sharing, transmission of force, and shock absorption, in addition to joint lubrication. It is important to understand that after a ligament injury the menisci are vulnerable to further damage because of the instability of the stifle. Maintaining proper restriction during recovery by avoiding all stressful actions like running & jumping will minimize the risk of further meniscal injury, as well as provide the best conditions for the re-stabilization of the stifle and healing of any meniscal injuries that occured at the time of the original ligament damage.
The menisci are ‘fibrocartilaginous’ structures which can be thought of as spongy elastic pads between the bones at the joint, composed predominately of collagen and open space filled with joint fluid. The menisci contribute significantly to joint lubrication. The fluid of the joint moves through the porous structure of the menisci. Because 70+% of the total weight of menisci is fluid, normal movement causes compression of the menisci which squeezes fluid out from them into the joint space to allow smoother gliding of the joint surfaces. The menisci re-expand when the pressure is reduced, drawing in fluid. This pumping action also helps to distribute synovial fluid throughout the joint and aids in the nutrition of the articular cartilage.
By compressing under a load, the menisci also act as shock absorbers, absorbing energy and reducing the shock to the adjacent cartilage and subchondral bone. The menisci protect the cartilage by acting as buffers between the surfaces of the femur and tibia where they meet and move against each other at the joint. The menisci transmit forces across the knee joint. The menisci provide added mechanical stability to the normal gliding of the femur on the tibia by deepening the surface of the tibial plateau to increase the congruity between the femoral condyles and the tibial plateau.