Relationship of medial plica and medial femoral condyle during flexion.

BACKGROUND: The goal of this study was to investigate the kinematic relationship between medial plica and medial femoral condyle during knee motion.

METHODS: I prospectively selected 30 knees which had different size of medial plica from patients underwent arthroscopic surgery over a one-year-period. I located the inner margins of these plicae by inserting needles percutaneously under direct vision during arthroscopic examination. The topographic changes of the margins of these plicae during knee motion were recorded by fluoroscopy and analyzed.

FINDINGS: Three types of medial plicae were defined by their size. In all types of the medial plicae, shifting (rubbing, sliding) medially was found when the knee was moved from extension to flexion. They remained in contact with the medial femoral condyles during the whole range of motion.

INTERPRETATION: This observation disclosed the kinematic relationship of the medial plica with the medial femoral condyle during knee motion in vivo. This pattern of medial-lateral motion may generate some shearing force acting on the cartilage of the medial femoral condyle. The conclusion of this study may draw more attention to the role of medial plica in the pathogenesis of degeneration of the cartilage on the medial femoral condyle of the knee joint.