Lateral meniscus injuries have more impact on pivot shift than anterolateral complex injuries in anterior cruciate ligament-injured knees.

Purpose: The purpose of this prospective study was to investigate the effect of Kaplan fibres (KF), anterolateral ligament (ALL) and lateral meniscus (LM) injuries on preoperative anterolateral rotational instability (ALRI) in anterior cruciate ligament (ACL)-injured knees. It was hypothesised that injuries to the ALC (i.e., KF and ALL) and to the LM would increase the preoperative anterolateral rotatory knee instability (ALRI) quantified by the pivot shift (PS) test.

Methods: A prospective registry study was conducted and patients who underwent primary unilateral ACL reconstruction were included. The PS test was preoperatively performed and quantified using the PIVOT iPad application. The anterior translation of the lateral tibia plateau (ATLT) was measured and the side-to-side difference (SSD) was calculated. The PS test was additionally graded according to IKDC criteria. Injuries to the KF, ALL and LM were diagnosed on acute preoperative magnetic resonance imaging (MRI) scans. Student's t-test was used to compare means and binary regression analysis was used to calculate odds ratio (OR). Statistical significance was set to p < 0.05.

Results: One hundred and twenty-four patients with a mean age of 29.9 ± 11.2 years were included in this study (61% male, 61% right knees). Patients with a LM injury showed a higher likelihood of having a high-grade PS (odds ratio [OR] = 2.5, p = 0.045). Complete radial meniscus tears of the LM significantly increased the ATLT in the quantified PS test compared to patients with an intact meniscus (p < 0.05). Injuries to the ALL, to the KF or a combination of both were not associated with high-grade PS or an increased ATLT.

Conclusion: Concomitant LM tears were associated with a clinical high-grade PS. Complete radial meniscus tears of the lateral meniscus significantly increased the ATLT compared to intact meniscus. Injuries to the ALL or to the KF were not associated with high-grade PS or an increased ATLT. This study provides new clinical evidence that concomitant LM injuries contributes to increased ALRI, highlighting the importance of addressing these structures during ACL reconstruction to optimise rotational instability.

Level of evidence: Level III, diagnostic studies.