Multiple secondary stabiliser injuries increase rotational instability in anterior cruciate ligament-deficient knees.

Purpose: Medial meniscus ramp lesions (MMRLs), lateral meniscus posterior root tears (LMPRTs), and anterolateral complex injuries (ALCIs) are major secondary stabiliser injuries associated with anterior cruciate ligament (ACL) injuries. This study aimed to investigate the effect of the number of secondary stabiliser injuries on knee instability in ACL injuries.

Methods: Patients who underwent primary ACL reconstruction between January 2017 and May 2023 were enroled in this study. Exclusion criteria encompassed patients with other ligament injuries, a history of contralateral knee injury, hyperextension, flexion contracture and meniscus injuries other than MMRL or LMPRT. Ultimately, 158 patients (mean age: 25.3 years; 81 males and 77 females) were included in this study, and the presence of MMRL, LMPRT and ALCI was investigated. Patients were categorised into four groups based on the number of ACL and secondary stabiliser injuries: single (isolated ACL injury), dual, triad and tetrad. Subsequently, the groups were compared regarding pivot shift grade, quantitative rotational instability measured using an inertial sensor, and anterior tibial translation (ATT).

Results: Secondary stabiliser injuries identified included ALCI 85 (53.8%), MMRL 58 (36.7%) and LMPRT 23 (14.6%). The distribution of patients in the single, dual, triad and tetrad groups was 45 (28.5%), 68 (43.0%), 37 (23.4%) and 8 (5.1%), respectively. High-grade pivot shifts were observed in 33.3% (15 out of 45) of the single group, 63.2% (43 out of 68) of the dual group, 67.6% (25 out of 37) of the triad group, and 100% (8 out of 8) of the tetrad group. Quantitative evaluations using the inertial sensor revealed significantly lower acceleration in the isolated ACL injury group compared to the other groups (p < 0.05). No significant difference was observed in ATT measurements (n.s.).

Conclusion: The combination of secondary stabiliser injuries led to higher instability. Therefore, it is important to carefully diagnose these injuries and devise appropriate treatment plans, particularly in cases of high knee instability.

Level Of Evidence: Level III diagnostic.