The M-shaped posterior cruciate ligament was associated with anterolateral ligament injury after anterior cruciate ligament injuries - a 1:2 age-and sex-matched cohort study

Sep 29, 2026

Magnetic resonance imaging (MRI) is used to diagnose anterior cruciate ligament (ACL) injuries, but the clinical meaning of posterior cruciate ligament (PCL) morphological changes—especially an M-shaped PCL—after ACL trauma remains poorly defined. This retrospective cohort study reviewed 281 arthroscopically confirmed noncontact ACL injury cases (2018–2023). M-shaped PCL status on preoperative MRI was evaluated for associations with meniscal and ligamentous injuries, including the anterolateral ligament (ALL). Results link M-shaped PCL to higher ALL injury incidence and show predictors within the M-shaped subgroup.

LanguageEnglish

CategoryHealthcare

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Pages12

Reading Time30 min

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Introduction

Cai etal. BMC Musculoskeletal Disorders (2026) 27:7 [https://doi.org/10.1186/s12891-025-08695-9](https://doi.org/10.1186/s12891-025-08695-9) BMC Musculoskeletal Disorders RESEARCH Open Access The M-shaped posterior cruciate ligament was associated with anterolateral ligament injury after anterior cruciate ligament injuries: a 1:2 age-and sex-matched cohort study Yifan Cai1,2†, Laiwei Guo1,2†, Zheng Zhang1,2†, Zhenxing Yan1,2, Pengan Yan1,2, Hua Han1,2, Bin Geng1,2, Yayi Xia1,2* and Yuanjun Teng1,3,4* Abstract Background Magnetic resonance imaging (MRI) is a reliable diagnostic tool for anterior cruciate ligament (ACL) injuries. Nonetheless, the clinical relevance of morphological changes in the posterior cruciate ligament (PCL), such as the M-shaped PCL, following ACL injuries has not been well studied. This study aimed to investigate whether the presence of M-shaped PCL was associated with meniscal and ligamentous injuries in patients with ACL injuries. Methods From May 2018 to May 2023, a total of 281 patients diagnosed noncontact ACL injuries with arthroscopy were retrospectively reviewed. The preoperative MRI images were examined to identify the presence of M-shaped PCL. Thirty-five patients with an M-shaped PCL were included in the study group, while 70 patients with non-Mshaped PCL were matched using 1:2 ratio by age (within 2 years) and sex to the control group. Key anatomical factors of the femur and tibia, including femoral notch width (NW), bicondylar width (BCW), notch width index (NWI), medial tibial depth (MTD), static anterior tibial subluxation (SATS), medial tibial slope (MTS), lateral tibial slope (LTS), as well as the status of meniscal and ligamentous injuries including medial and lateral menisci (LM), medial and lateral collateral ligaments, and anterolateral ligament (ALL) were assessed using MRI. The Spearman correlation coefficientsand multivariate logistic regression were applied to analyze potential predictors of M-shaped PCL. Results The mean age of all patients was 34.7 ± 10.2 years, and the male-to-female ratio was 3:4 in each group. The incidence of M-shaped PCL was 12.4% . The study group demonstrated a higher proportion of ALL injuries compared to the control group (54 . 3% vs 31 .4%, respectively; p = 0 . 024) . In all patients, the presence of M-shaped PCL independently predicted ALL injury (p = 0 . 021) . In the M-shaped PCL group, ALL injury was associated with NW (ρ = 0 . 372; p = 0 . 028), BCW (ρ = 0 . 380; p = 0 . 024), and SATS (ρ = 0 .437; p = 0 . 009) . Additionally, LM lesions (p = 0 . 041), a larger NW †These authors contributed equally to this work and should be considered asco-first authors. *Correspondence: Yayi Xia [xiayayilzu@126.com](xiayayilzu@126.com)[ ](xiayayilzu@126.com)Yuanjun Teng [tengyj06@126.com](tengyj06@126.com) Full list of author information is available at the end of the article © The Author(s) 2025. Open Access This article is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License, which permits any non-commercial use, sharing, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if you modified the licensed material. You do not have permission under this licence to share adapted material derived from this article or parts of it. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit [http://creativecommons.org/licenses/by-nc-nd/4.0/](http://creativecommons.org/li

FAQs

What was the study’s main objective?

To determine whether the presence of an M-shaped posterior cruciate ligament (PCL) after ACL injury is associated with meniscal and other ligamentous injuries, including the anterolateral ligament (ALL).

How were patients selected and matched in the study?

From May 2018 to May 2023, 281 patients with arthroscopy-confirmed noncontact ACL injuries were retrospectively reviewed. Thirty-five patients with an M-shaped PCL were matched to 70 non-M-shaped PCL controls using a 1:2 ratio by age (within 2 years) and sex.

What were the key findings regarding ALL injury?

The incidence of M-shaped PCL was 12.4%. The M-shaped PCL group showed a higher proportion of ALL injuries than the control group, and in all patients, M-shaped PCL independently predicted ALL injury.

Sep 29, 2026

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