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Background: To determine the association between time from injury to ACL reconstruction (Time Injury-ACLR ) and biochemical markers of cartilage metabolism and inflammation six months following ACL reconstruction (ACLR)., Methods: Individuals with a unilateral ACL injury were enrolled at initial presentation in the orthopedic clinic; blood was collected six months following ACLR. Enzyme-linked immunosorbent assays were used to analyze the ratio of serum concentrations of type-II collagen breakdown (C2C) to synthesis (CPII), plasma matrix metalloproteinase-3 (MMP-3), interleukin-6 (IL-6), and serum aggrecan neoepitope (ARGS). We used separate linear regressions to assess associations between biochemical markers and Time Injury-ACLR ., Results: Twenty-two participants (50% females, mean [SD], age 21.9 [4.5] years old; BMI 23.8 [2.6] kg/m 2 ) completed the study. Time Injury-ACLR ranged from nine to 67days (31.0 [14.4days]). Greater Time Injury-ACLR predicted greater serum C2C:CPII ratios six months following ACLR (C2C:CPII=0.15 [0.02], R 2 =0.213, P=0.030). Males (R 2 =0.733, P=0.001) but not females (R 2 =0.030, P=0.609) demonstrated a significant association between greater C2C:CPII and Time Injury-ACLR at the six-month follow-up exam. Time Injury-ACLR did not associate with IL-6, MMP-3, or ARGS at six months., Conclusions: Greater time between injury and ACL reconstruction was associated with greater serum C2C:CPII six months following ACLR in males but not females, and IL-6, MMP-3, and ARGS levels were not associated with Time Injury-ACLR in males or females. The time between ACL injury and ACLR may affect collagen metabolism in males and should be further investigated in a larger study along with other patient-relevant outcomes., (Copyright © 2018 Elsevier B.V. All rights reserved.)