Kinematics of Normal Menisci during Knee Flexion

The human knee menisci are important structures to, proper knee joint function. At present, little data exists describing the meniscal kinematics of the intact knee. Accordingly, the purpose of this study was to determine in-vivo meniscal kinematic motion of the non-injured knee during unloaded knee flexion through use of magnetic resonance imaging (MRI). Seven females and three males (mean age = 27.6 yrs. +/7.7 yrs.) who denied previous history of knee injury, were examined by magnetic resonance imaging (MRI) throughout a full range of motion at 0, 60, and 120 degrees of knee flexion. Computer two-dimensional images of the menisci were generated and evaluated quantitatively for anteroposterior excursion. Deformation was evaluated qualitatively. During flexion, the posterior excursion of medial meniscus was 6.2 mm, while that of the lateral meniscus was 8.2 mm. The lateral meniscus is relatively more mobile. The anterior horn segments were shown to be more mobile than the posterior horn segments except for the lateral meniscus and indicates that this meniscus moves more as a single unit. The medial meniscus has been shown to be constrained in the posterior horn, a site of frequent tear. The menisci also act to fill the void created by the incongruous femoral condyles and tibial plateau, and thereby enhance joint stability. Prior limitations of meniscal kinematic assessment may be overcome with advanced imaging techniques such as magnetic resonance imaging. The menisci are highly mobile and easily deformed structures within the intact knee joint. This imaging technique may prove useful in the elucidation of meniscal dynamics. In conclusion, this study revealed that MRI can be used as a noninvasive method to determine in-vivo meniscal motion. In addition, the amount of kinematic motion was menisci and horn dependent. In the future, similar techniques may be applied clinically to aid in the diagnosis of joint dysfunction.