Determination of Normal Reference Values for Meniscal Extrusion Using Ultrasonography During the Different Range of Motion: A Pilot, Feasibility Study.

Objectives: It is essential to know the normal extrusion measures in order to detect pathological ones. In this study, we aimed to define some normal reference values for meniscal extrusion in the normal knees during different ranges of motion.

Methods: The amount of anterior and posterior portion of meniscal extrusion among 21 asymptomatic volunteers (42 knees) were tracked in 0, 45, and 90° of knee flexion using an ultrasound machine. The repeated measures analysis of variance (ANOVA) was used to show the interaction between the amounts of meniscal extrusion and the different degrees of knee flexion.

Results: The anterior portion of the lateral menisci at full knee extension (0.59 ± 1.40) and the posterior portion of the medial menisci during 90° flexion (3.06 ± 2.36) showed the smallest and the highest mean amount of extrusion, respectively. The normal average amounts of anterior extrusion were 1.12 ± 1.17 and 0.99 ± 1.34 mm for medial and lateral menisci, respectively. The posterior meniscal normal extrusions were significantly increasing in both medial and lateral menisci during the survey (F = 20.250 and 11.298; both P values <.001) as they were measured 2.37 ± 2.16 and 1.53 ± 2.18 mm in order.

Conclusions: The medial meniscus can extrude 1.74 ± 1.84 mm normally while this amount was 1.26 ± 1.82 mm for the lateral meniscus. These measures commonly increased with the rising of knee flexion motion. Likewise, the posterior portion showed more extrusion than the anterior portion on both sides. These measures commonly increased with higher knee flexion.