Shelbourne and colleagues reviewed 169 patients who underwent reconstruction after an acute ACL injury and evaluated the impact of timing of surgery and aggressive rehabilitation on patient outcomes. There was a trend toward increased odds of joint adhesions in patients reconstructed within 1 week after injury compared to those reconstructed 3 weeks after injury. Interestingly, patients who underwent reconstruction within 1-3 weeks of injury with active rehabilitation had a lower incidence of joint adhesions compared to those who underwent conventional rehabilitation. However, this study is more than 20 years old and there are many new developments in the management of the acute phase of ACL reconstruction and surgical techniques, therefore, we should be rational about the results of this trial.Shelbournet and Patel reviewed some perioperative considerations that must be fully taken into account preoperatively. The authors concluded that preoperative psychological preparation, surgical schedule, knee-related diseases and knee conditions (e.g., presence of swelling, adequate muscle strength, joint mobility) should be fully considered to determine the optimal timing of surgery. In addition, Almekinders and colleagues studied 70 adult patients who underwent ACL reconstruction surgery using autologous bone-tendon-bone. For patients who underwent surgery within 1 month, there was limited joint motion in the early postoperative recovery period; however, after 1 year, there was no significant difference in joint motion between those who underwent surgery early and those who underwent surgery late.Passler13 et al. evaluated postoperative complications in 283 patients who intervened on the timing of surgery. For patients who underwent surgery within 7 days of injury, approximately 18% developed joint adhesions, compared to only 6% of those who underwent surgery after 4 weeks. However, Bottoni and colleagues found no difference in joint mobility between those who had surgery early and those who had surgery after 6 weeks. However, the patients who participated in this study were all active duty military personnel and were not fully representative of the general population, and the sample was not universal. Mayr et al14 studied the effect of timing of surgery and preoperative knee status on healing. The authors have demonstrated: knee stress (e.g., swelling, oozing, elevated skin temperature, etc.), joint mobility, and additional injury. The authors reported a correlation between reconstruction performed 4 weeks after injury and joint adhesions, however, the authors also found a strong correlation between preoperative knee stress and adhesions as well. Interestingly, patients with joint stress who underwent surgery 4 weeks after injury had the same incidence of joint adhesions as those who underwent surgery earlier. Inadequate preoperative joint flexion and extension mobility is also a sign of postoperative adhesions. The findings suggest that the preoperative status of the knee will be more important in determining the optimal timing of surgery than simply when to perform the surgery. Conversely, delayed reconstruction is another topic of interest regarding the optimal timing of ACL reconstruction. The definition of delayed versus early reconstruction will vary from author to author, therefore, detailed explanations and descriptions of the results are needed in the text. For example, Frobell et al. defined early reconstruction as completion of surgery within 10 weeks after injury; he did not explicitly define delayed reconstruction, but in their studies, delayed reconstruction was defined as completion of surgery within 5.5 to 19 months in all cases. In addition, Meighan et al. defined early reconstruction as surgery within 2 weeks and delayed reconstruction as surgery at 8-12 weeks. patients with poor ACL are usually associated with knee instability, which can lead to further knee injuries such as meniscal tears, cartilage defects, and ligament tears. church and Keating18 reviewed 183 patients with ACL reconstruction to analyze the relationship between postoperative meniscal tears and correlation of knee degeneration with the time to surgery after injury. The results showed that surgery 1 year after injury increased the incidence of meniscal tears. Also by the SFA system, surgery 12 months after injury was found to increase the incidence of degenerative joint degeneration. Regarding the correlation between the timing of ACL reconstruction and meniscal injury and cartilage defects, Kennedy et al19 found similar results. Athletes who underwent ACL reconstruction 1 year after their initial injury had a significantly higher chance of having a medial meniscal tear. However, there was no significant correlation between lateral meniscus injury and timing of surgery. The authors also found a higher incidence of knee degeneration in patients who had surgery 6 months after injury.20 Ahlen and colleagues20 found that Lysholm knee scores and Tegner knee scores were higher in patients who had surgery within 5 months after injury than in patients who had surgery 24 months after injury. There was no statistically significant difference in the incidence of meniscal tears between the groups, but the authors noted that this may have been due to low sample size. A large number of Norwegian ACL reconstruction cases were selected for study by Granan et al. The authors analyzed 3699 patients with initial ACL reconstruction to explore the correlation between the timing of surgical intervention and more pathological changes. No correlation was found with articular cartilage or meniscal lesions in the pediatric (16 years and younger) group of patients, but in the younger (17-40 years) and middle-aged (41 years and older) groups, a 1-month delay in surgery was found to increase the incidence of articular cartilage disease by 1%. The choice of timing of ACL reconstruction has important implications for patient healing. Although there is no uniformity in the literature, there is a general tendency regarding the timing of reconstruction. Most scholars believe that ACL reconstruction should be completed within 3 weeks after injury to minimize joint adhesions. In addition to timing, some objective conditions including perioperative swelling, oozing, and joint mobility are also important indications to determine the timing of surgery. Preoperative quadriceps strength can also affect the healing of ACL reconstruction; Eitzen et al. found that leg strength was significantly affected 2 years after surgery if patients had a 20% or greater decrease in quadriceps muscle strength. Therefore, the authors recommended that surgery be performed only when the patient has achieved more than 80% of the muscle strength of the healthy lower limb. When deciding on the optimal timing of surgery, it may not be possible to consider only the timing of the procedure, as it is determined by a combination of factors, such as preoperative knee status, family, school and work situations, and patient psychological preparation. Additional research is needed to determine a multifactorial algorithm to assess when a patient should have surgery to ensure the best clinical outcome. In this article, there is no clear definition of early versus delayed reconstruction. In many studies, no two studies have defined early or delayed reconstruction in the same way.Church and Keating18 used a 12-month cut-off for early versus delayed reconstruction.Bottoni et al. concluded that early reconstruction should be performed as early as possible and delayed reconstruction at least 6 weeks after injury. Due to the wide variability in the timing of surgery after injury, overall approximately one-third of acute phase ACL reconstructions are favorable to delineate a clear time boundary. As surgical techniques have improved, postoperative rehabilitation has also improved to a great extent. Current surgical techniques allow for rapid rehabilitation after ACL reconstruction with a focus on early activity, weight bearing, and lower extremity strength exercises. As surgical techniques and rapid rehabilitation evolve, more research is needed to determine the effect of acute inflammation of the knee on ACL reconstruction, as well as to examine other structures within the joint that may have an impact on the long-term outcome of the procedure. Early reconstruction may be chosen by some athletes because they expect an early return to competition, and conversely, delayed reconstruction is chosen by another group of individuals who have more time to spare and want more adequate preoperative preparation. Both early ACL reconstruction and late reconstruction have a number of potential complications that can affect clinical outcomes. Medical professionals (both therapists and operators) should take these morbidities into full consideration when talking to patients about the best timing for surgery. Therefore, therapists should also routinely browse more literature so as to give patients more, accurate, and effective guidance regarding ACL reconstruction.