Spontaneous Healing of Meniscal Tears With ACL Injuries and Its Impact on Timing of ACL Surgery

Acute anterior cruciate ligament (ACL) tears with meniscal injuries elevate posttraumatic osteoarthritis risk. While early ACL reconstruction (ACLR) remains prevalent, emerging evidence suggests that delayed intervention may enhance meniscal preservation.

To quantify location/morphology-specific spontaneous healing trajectories of meniscal tears and establish temporal thresholds for surgical decision-making.

Cohort study; Level of evidence, 3.

Patients who underwent ACLR at a tertiary academic medical center specializing in sports medicine from January 2020 to December 2023 were included in this study. Demographic profiles and time-to-surgery intervals were extracted from electronic medical records. Patients were stratified by injury-to-surgery interval in detail: 0-1week, 1-2 weeks, 2-3 weeks, 3-4 weeks, 4-6 weeks, 6-8 weeks, 8-12 weeks, 12-16 weeks, 16-20 weeks, and 20-24 weeks. Meniscal tear characteristics were classified via preoperative magnetic resonance imaging (MRI) and intraoperative arthroscopic evaluation (location: anterior horn, body, and posterior horn; morphology: longitudinal, compound, horizontal, and radial). Spontaneous healing of the meniscus was defined as a complete fibrous union observed during arthroscopic evaluation.

A total of 2723 patients (3562 menisci) were included, including 2493 with lateral meniscal tears and 2001 with medial meniscal (MM) tears. The overall spontaneous healing rate of lateral meniscal (LM) tears is higher than that of MM tears (7.06% vs 1%; P < .001). Additionally, the highest healing rate was observed in longitudinal tears of the LM posterior horn (11.35%). The overall trend of the spontaneous healing rate of meniscal injuries in the setting of ACL tears increased over time during the first 8 to 12 weeks after the injury. The spontaneous healing rate was highest at 12 weeks and subsequently declined thereafter. Comparative analysis demonstrated a significant increase in the healing rate in the 8-12 weeks intervention group versus the delayed groups: the LM healing rate decreased from 15.87% to 9.81% (longitudinal tears: 34.04% vs 17.72%; radial tears: 22.97% vs 7.08%), and the MM rate decreased from 2.65% to 1.36%. Compared with the mean level of early intervention groups (≤8 weeks), the 8-12 weeks group showed >1.5 times increase in healing rates (LM: 15.87% vs 6.29%; longitudinal tears: 34.04% vs 9.83%; radial tears: 22.97% vs 8.65%; MM: 2.65% vs 0.86%).

Delaying ACLR to 8 to 12 weeks after injury may optimize the potential for spontaneous healing in LM injuries (particularly posterior horn longitudinal and radial tears), potentially increasing meniscal healing rates by 1.5 to 2.5 times compared with early intervention (≤8 weeks). The healing potential of LM tears, particularly posterior horn longitudinal and radial tears, was greater than that of MM tears in this study.