Surgery Timing
When ACL reconstruction is indicated, moderate evidence supports reconstruction within five months of injury to protect the articular cartilage and menisci.

With respect to performing ACL reconstruction early following injury, three moderate strength studies evaluated the effect of timing on outcome following ACL reconstruction.17, 56, 76 Post-operative range of motion was not different if surgery was performed within 48 hours of injury, within 3-7 days of injury, or within 2 weeks of injury; or if surgery was delayed more than 3 weeks of injury, delayed for a minimum of 6 weeks of injury, or delayed for 8-12 weeks of injury. 17, 56, 76 Strength and stability by KT 1000 were also not different between early and delayed ACL reconstruction.56, 76 However, performing ACL reconstruction early, within three weeks of injury, increased the rate of re-operation form 0% to 8%. Complications included pain with extension (n=11), meniscus tear (n=1), and failed ACL reconstruction (n=2;).56
With respect to delaying ACL reconstruction to a time point past the injury, there were two high-strength studies of same cohort of patients and three moderate-strength studies that compared early (within 3-5 months from injury) versus late (after 3-5 months from injury) ACL reconstruction. 10, 24, 33, 35, 36 Early reconstruction improved objective knee stability as measured by the Lachman test and pivot shift test.83, 84 Three studies demonstrated a higher activity level in the patients that underwent early ACL reconstruction. 10, 33, 35, 36 One study reported higher function in patients that underwent early ACL reconstruction.24
Early reconstruction also decreased the incidence of meniscus tears from 62% to 37% and decreased the incidence of subsequent meniscectomy surgery from 44% to 8%.10, 35 One moderate-strength study stratified outcome by meniscus injury, which was not emphasized in the high-strength study but was supported by their data.10,35 Further, in the setting of meniscus treatment, the rate of meniscal repair was 29% with early ACL reconstruction and 12% when ACL reconstruction was delayed beyond 3 months.
The importance of this recommendation was based on improving patient function and protecting the knee with ACL injury from further meniscus injury, which could reduce the risk for premature osteoarthritis
Possible Harms of Implementation
The decision to perform early ACL reconstruction could lead to loss of motion, joint stiffness, and reoperation if sound history and physical examination is not performed.
Future Research
Randomized control trials should be performed to better understand the effect of timing of ACL reconstruction on range of motion, rate of reoperation, and clinical outcome of patients.