Background: Anterior Cruciate ligament reconstruction (ACLR) is one of the most common surgeries performed in orthopedics. The optimal timepoint for ACLR is not consistently defined. Our study aimed to address this gap by comparing patient-reported outcomes (PROs) in acute versus chronic ACLR groups using 60 days as a marker for chronicity.

Methods: This historical cohort study was based on prospectively collected PROs following ACLR. Inclusion criteria were based on complete pre-operative and 2-year follow-up. Patients were categorized as acute with an injury to surgery interval of less than 60 days, those over 60 days were considered chronic. Descriptive analysis was conducted using Fisher’s exact tests and Chi-square analysis. A mixed linear model regression analysis was conducted to examine the effect of time on outcome variables using Restricted Maximum Likelihood (REML) across two groups (acute and chronic). The dependent variables were: IKDC Score, EuroQol Score, PROMIS Global Mental and Physical Health Scores, KOOS Score, and VAS Pain Score with time as the primary fixed effect. Data was analyzed using Python version 3.8 with pandas and statsmodels packages.

Results: 97 out of 1235 patients from the institutional database met the inclusion criteria, with 54 chronic, 43 acute, 62 males, 35 females, and a median age at the time of surgery of 28 21, 40. The median BMI was 25.2 23, 28.2, 26.6 23.3, 30.1 for chronic cases and 24.2 22.6, 26.8 for acute cases (p < 0.011). ACL grafts included 25 autografts and 72 allografts. Autograft was used more frequently in acute cases (p < 0.011), while chronic cases had an increased use of allografts (p < 0.011). Overall median PROs improved: from 50.6 to 86.2 (IKDC), 0.7 to 0.8 (EuroQol), 56 to 59 (PROMIS Global Mental Health), 50.8 to 57.7 (PROMIS Global Physical Health), 66 to 92 (KOOS), and 3 to 1 (VAS Pain). Linear mixed model analysis revealed a significant positive effect of time on IKDC (p < 0.001), and a random effects analysis demonstrated a group variance of 2.355, indicating variability in IKDC scores between acute and chronic groups.

Conclusion: Using a 60-day cut-off for defining acute versus chronic ACLR showed greater improvement in median PROs. The IKDC score is a valuable predictor to compare acute versus chronic ACL injuries using 60 days as a cutoff for chronicity. Using this marker may aid in optimizing future surgical timing and recommendations that will improve individual patient recovery.