Radial displacement of the lateral meniscus before and after anterior cruciate ligament reconstruction.

INTRODUCTION: The purpose of this study was to investigate radial displacement (RD) of the lateral meniscus in patients with anterior cruciate ligament (ACL) injury by using magnetic resonance imaging both pre- and post-operatively.
MATERIALS AND METHODS: This study included 59 knees that had undergone ACL reconstruction. The length that extruded from the lateral tibial plateau was measured in the coronal plane.
RESULTS: Mean pre-operative RD was 1.8 mm, and mean post-operative RD was 2.4 mm (P < 0.001). Mean pre-operative RD was 1.6 mm in the group with lateral meniscus tears <1 cm, and 2.8 mm in the group with tears ≥1 cm (P = 0.033); the corresponding post-operative values were 2.1 and 3.2 mm (P = 0.038), respectively. Mean pre-operative RD was 1.9 mm in the longitudinal tear group and 2.4 mm in the radial tear, flap tear, or complex tear group (P = 0.21); the corresponding post-operative values were 2.2 and 4.1 mm (P = 0.036), respectively.
CONCLUSION: We found that RD of the lateral meniscus was not a rare finding, and that RD was related to the meniscus status. Moreover, RD did not improve after ACL reconstruction. Thus, the treatment for meniscus tear should be carefully assessed. Level of evidence Level 4, case series, therapeutic studies.