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Background: The role of meniscal lesions and repair in combination with anterior cruciate ligament (ACL) injury and reconstruction has not been extensively investigated in vivo and under weightbearing conditions. Purpose: The purposes of this study were to (1) compare the in vivo knee kinematics between patients with ACL tear and those with combined ACL and medial meniscal tears and (2) investigate kinematic differences between isolated ACL reconstruction and ACL reconstruction plus medial meniscal repair (MR). It was hypothesized that concomitant posterior horn medial meniscal tear and ACL deficiency would affect knee internal-external rotation and anterior-posterior translation but MR would restore these parameters. Study Design: Controlled laboratory study. Methods: Nineteen patients who underwent ACL reconstruction were included: 10 had intact menisci (IM group) and 9 had a medial meniscal injury that was repaired during ACL reconstruction using an all-inside technique (MR group). Preoperatively and 18 months postoperatively, active knee kinematics under weightbearing conditions was evaluated during a single-leg squat using a dynamic biplane x-ray imaging system. The general linear model was used to investigate the differences between group (IM vs MR) and time (preoperative vs follow-up) and their interactions. Results: Tibial internal rotation was higher in the MR group than the IM group both before and after surgery (P =.007). Knee valgus rotation was higher in the MR group preoperatively (P <.001), while no differences were found postoperatively because of an increase of valgus rotation in the IM group, which was significant in the descendant phase (P <.001). Preoperatively, the IM group showed a more medial tibial translation compared with the MR group in the descendant phase (P =.006). Conclusion: When performing a single-leg squat, patients with ACL-deficient knees and a medial meniscal tear demonstrated a more valgus rotation, tibial internal rotation, and lateral tibial translation versus those with intact menisci. After ACL reconstruction and MR, these patients demonstrated significantly higher tibial internal rotation when compared with patients who underwent isolated ACL reconstruction. Clinical Relevance: Surgeons should be aware that MR does not fully restore knee kinematics in vivo and under weightbearing conditions in the context of ACL reconstruction. [ABSTRACT FROM AUTHOR]

Background: The anterior cruciate ligament (ACL) is a primary restraint to anteroposterior as well as rotatory knee laxity. In case of concomitant lesion of menisci or other ligamentous structures, further dynamic instability is encountered. A lateral extra-articular tenodesis (LET) augmentation has been proposed by the Authors to treat or prevent residual laxity. Indications: ACL reconstruction is recommended in young athletes involved in pivoting sports, non-contact pivoting injuries, high-grade pivot shift, deep notch sign and double bone bruise, meniscal loss, and revision of previous bone-patellar tendon-bone autograft. Technique Description: A 2 to 3 cm oblique incision is made over the pes anserinus. Gracilis and semitendinosus tendons are harvested with their attachment preserved and sutured together. Tibial tunnel is reamed after positioning of a guide pin. A wire-loop passer is directed from the tibial tunnel to the anteromedial portal. A 2 to 3 cm longitudinal incision is made superior-laterally, the ileotibial band is divided and retracted anteriorly. A suture-loop is retrieved from the lateral incision through the anteromedial portal with a curved Kelly clamp. The suture is placed into the wire-loop and retrieved with it from the tibial tunnel. The graft is retrieved from the lateral incision, tensioned with the knee at 70° to 90° of flexion and foot in neutral rotation and secured with 2 staples to the femur. A 1-cm skin incision is performed just below the Gerdy tubercle. The graft is retrieved from this incision below the fascia with a small Kelly clamp, tensioned and secured with a staple. The iliotibial tract defect is closed. Results: At long-term follow-up, a revision rate of 3% has been reported, while patient-reported outcome measures (PROMs) were excellent. At very-long-term follow-up, most patients were still involved in sports with a very low rate of positive Lachman and pivot shift tests. No overconstraint and lateral osteoarthritis were encountered. Medial osteoarthritis was related only to medial meniscectomy. Discussion/Conclusion: The ACL reconstruction plus LET over-the-top technique is a safe and reliable surgery with a low rate of reoperations and peri-operative complications at very-long-term follow-up. Patient Consent Disclosure Statement: The author(s) attests that consent has been obtained from any patient(s) appearing in this publication. If the individual may be identifiable, the author(s) has included a statement of release or other written form of approval from the patient(s) with this submission for publication. Graphical Abstract This is a visual representation of the abstract. [ABSTRACT FROM AUTHOR]

This article presents with an evidence based approach, the kinematical rationale, biological evidence and the long term results of the "Over-The-Top" anterior cruciate ligament reconstruction with lateral plasty technique. This surgery was developed more than 25 years ago at the Rizzoli Institute by professor Marcacci and Zaffagnini and it is still widely performed in many orthopedic center worldwide. [ABSTRACT FROM AUTHOR]

Figure Graph: Figure 1 This 3D rendering shows the relationships between anatomical landmarks of the knee and the direction of the iliotibial band with an intact ACL and injured ACL. After performing many video analysis studies, especially on footballers [[13], [15]], and tridimensional bone models of ACL injuries [[17]], we reached the conclusion that at the moment of ACL injury, a real "subluxation" with anterior translation, valgus deviation and tibial proximalization occurs. In trying to delineate the clinical relevance of Kaplan fiber complex injuries, we have to keep in mind the knee anatomy in relation with the ACL injury mechanism. At the time of ACL injury, the knee joint increases its flexion, from early degrees (near 10-20°) at the time of the foot strike and following ACL rupture to more than 30-40° after the ligamentous rupture [[18]]; thus, posterior sliding of the ITB is supposed. [Extracted from the article]

Anterior cruciate ligament (ACL) tear is one of the most common sport-related injuries and the request for ACL reconstructions is increasing nowadays. Unfortunately, ACL graft failures are reported in up to 34.2% in athletes, representing a traumatic and career-threatening event. It can be convenient to understand the various risk factors for ACL failure, in order to properly inform the patients about the expected outcomes and to minimize the chance of poor results. In literature, a multitude of studies have been performed on the failure risks after ACL reconstruction, but the huge amount of data may generate much confusion. The aim of this review is to resume the data collected from literature on the risk of graft failure after ACL reconstruction in athletes, focusing on the following three key points: individuate the predisposing factors to ACL reconstruction failure, analyze surgical aspects which may have significant impact on outcomes, highlight the current criteria regarding safe return to sport after ACL reconstruction. [ABSTRACT FROM AUTHOR]

Background: In adolescents, the rate of meniscal injury at the time of anterior cruciate ligament (ACL) reconstruction, the rate of ACL graft revision, and clinical outcomes has not yet been investigated. Hypothesis: In patients younger than 16 years, the rate of meniscal injuries at the time of ACL reconstruction increases with time from injury. The mid-term revision rate and reoperation rate after ACL reconstruction with hamstrings and lateral tenodesis are lower than those reported in literature for isolate ACL reconstruction. Study Design: Case series. Level of Evidence: Level 4. Methods: Patients younger than 16 years who underwent ACL reconstruction with hamstring and lateral tenodesis, with a follow-up ≥2 years were included. The number of meniscal lesions was stratified according to the delay between injury-to-surgery (<3, 3-12, >12 months). All reoperations, Lysholm score, Knee Injury and Osteoarthritis Outcome Score subscales for pain (at rest and during activity), and return to sport were collected. Results: A total of 151 patients (mean age 14.8 ± 1.2 years) were included. Patients undergoing surgery at <3 months after injury had a lower meniscal injury rate (36%) than those treated at 3 to 12 months (55%) and >12 months (63%) after injury (P = 0.04). Medial meniscal lesions were more likely to be repaired when surgery was performed <3 months after injury (91%). Subjective follow-up data were available for 132 patients, and 19 were lost to follow-up. At 6.0 ± 2.6 years, 6% of patients underwent ACL revision; 1 of 20 (5%) patients with posterior tibial slope ≥12° and 4 of 45 (9%) patients with Tegner level ≥8. Nine new meniscal procedures were performed; 19% of repaired menisci underwent meniscectomy. Good or excellent Lysholm score was reported by 88% of patients; 56% of patients with concurrent lateral meniscectomy had pain during activity, 91% returned to sport, and 79% were still participating at final follow-up. Conclusion: Patients younger than 16 years undergoing ACL reconstruction within 3 months from injury had the lowest rate of meniscal injuries. ACL reconstruction with lateral tenodesis had low revision rate (6%) and good or excellent clinical outcomes in 88% of young adolescents. Clinical Relevance: Sport physicians should be aware that adolescent patients undergoing ACL reconstruction within 3 months after injury have the lowest rate of meniscal injuries; the mid-term revision rate of ACL reconstruction with lateral plasty is lower than 10% and the patients' perceived outcomes are good with almost all patients returning to sport activity. [ABSTRACT FROM AUTHOR]

Background: Few studies on outcomes after anterior cruciate ligament (ACL) reconstruction (ACLR) have provided insight into the very long-term effects of this procedure. Purpose: To systematically review the outcomes, failure rate, incidence, and predictors of osteoarthritis (OA) for different ACLR techniques at a minimum 20-year follow-up. Study Design: Systematic review; Level of evidence, 4. Methods: A search of the PubMed, SCOPUS, and Cochrane databases was performed on June 2020 for studies of patients who underwent ACLR and had a minimum follow-up of 20 years. We extracted data on patient and surgical characteristics, patient-reported outcomes (Lysholm score, subjective International Knee Documentation Committee [IKDC] score, Knee injury and Osteoarthritis Outcome Score [KOOS], and Tegner score), clinical outcomes (IKDC grade, pivot shift, Lachman, and KT-1000 laxity), degree of OA (Kellgren-Lawrence, Ahlbäck, and IKDC OA grading), revisions, and failures. Relative risk (RR) of OA between the operated and contralateral knees was calculated as well as the pooled rate of revisions, failures, and conversion to total knee arthroplasty (TKA). Results: Included were 16 studies (N = 1771 patients; mean age, 24.8 years; mean follow-up, 22.7 years); 80% of the patients underwent single-bundle bone–patellar tendon–bone (BPTB) reconstruction. The average Lysholm (89.3), IKDC (78.6), and KOOS subscale scores were considered satisfactory. Overall, 33% of patients had "abnormal" or "severely abnormal" objective IKDC grade, 6.7% had KT-1000 laxity difference of ≥5 mm, 9.4% had Lachman ≥2+, and 6.4% had pivot shift ≥2+. Signs of OA were reported in 73.3% of patients, whereas severe OA was reported in 12.8%. The operated knee had a relative OA risk of 2.8 (P <.001) versus the contralateral knee. Identified risk factors for long-term OA were male sex, older age at surgery, delayed ACLR, meniscal or cartilage injuries, BPTB autograft, lateral plasty, nonideal tunnel placement, residual laxity, higher postoperative activity, and postoperative range of motion deficits. Overall, 7.9% of patients underwent revision, and 13.4% of ACLRs were considered failures. TKA was performed in 1.1% of patients. Conclusion: Most patients had satisfactory subjective outcomes 20 years after ACLR; however, abnormal anteroposterior or rotatory laxity was found in nearly 10% of cases. The presence of radiographic OA was high (RR 2.8 vs uninjured knee), especially in patients with concomitant meniscal or cartilage injuries, older age, and delayed surgery; however, severe OA was present in only 12.8% of cases, and TKA was required in only 1.1%. [ABSTRACT FROM AUTHOR]

Background: A combined injury to the anterior cruciate ligament (ACL) and medial collateral ligament (MCL) is a common injury pattern encountered during clinical practice. Recent systematic reviews have found no consensus on the optimal method of managing this combined ligament injury pattern, and no long-term studies with modern techniques are available in the literature. Purpose: To compare 2 groups of patients who underwent isolated ACL reconstruction in terms of failures and clinical scores at long-term follow-up. In the first group were patients with isolated ACL tears (ACL group), while the second was composed of patients with combined ACL and MCL grade 2 tears (ACL + MCL group). Study Design: Cohort study; Level of evidence, 3. Methods: A total of 57 patients (37 in the ACL group and 20 in the ACL + MCL group) underwent isolated ACL reconstruction with a double-bundle technique between January and December 2005. Patients were contacted for scores on the International Knee Documentation Committee subjective form, Western Ontario and McMaster Universities Osteoarthritis Index, and Tegner activity scale as well as data regarding ipsilateral or contralateral revision ACL surgery. A 2-way analysis of variance for repeated measures was used to statistically assess the differences between the groups. Results: Overall, 49 patients (86%) completed the survey and were therefore included in the study. The minimum follow-up was 14.6 years (range, 14.1-15.2 years). There was a significant reduction in both groups of all the outcome scores between the intermediate and final-follow-up. The number of failures was 3 of 31 (9.7%) in the ACL group and 1 of 18 (5.5%) in the ACL + MCL group; this difference was not significant. Moreover, there were no clinical differences between the groups in terms of graft failures, contralateral lesions, and clinical scores. Conclusion: At 14-year follow-up, no clinical difference or increased failure rate was observed between the study groups, suggesting that isolated ACL reconstruction could represent an appropriate treatment for a combined ACL and MCL grade 2 lesion. [ABSTRACT FROM AUTHOR]

Background: Lateral extra-articular tenodesis in the context of anterior cruciate ligament (ACL) reconstruction (ACLR) is performed to better control anterolateral knee instability in patients with high-grade preoperative pivot shift. However, some authors believe these procedures may cause lateral compartment overconstraint, affecting knee motion in daily life. Purpose/Hypothesis: The primary aim of the present study was to identify kinematic differences during the execution of an activity under weightbearing conditions between knees having undergone ACLR using anatomic single-bundle (SB) versus single-bundle plus lateral plasty (SBLP) techniques. The secondary aim was to compare the postoperative kinematic data with those from the same knees before ACLR and from the healthy contralateral knees in order to investigate if ACLR was able to restore physiologic knee biomechanics during squat execution. The hypotheses were that (1) the SBLP technique would allow a better restoration of internal-external (IE) knee rotation than would SB and (2) regardless of the technique, ACLR would not fully restore physiologic knee biomechanics. Study Design: Randomized controlled trial; Level of evidence, 2. Methods: In total, 32 patients (42 knees) were included in the study. Patients were asked to perform a single-leg squat before surgery (ACL-injured group, n = 32; healthy contralateral group, n = 10) and at minimum 18-month follow-up after ACLR (SB group, n = 9; SBLP group, n = 18). Knee motion was determined using a validated model-based tracking process that matched patient-specific magnetic resonance imaging bone models to dynamic biplane radiographic images under the principles of roentgen stereophotogrammetric analysis. Data processing was performed using specific software. The authors compared IE and varus-valgus rotations and anterior-posterior and medial-lateral translations among the groups. Results: The mean follow-up period was 21.7 ± 4.5 months. No kinematic differences were found between the SB and SBLP groups (P >.05). A more medial tibial position (P <.05) of the ACL-injured group was reported during the entire motor task and persisted after ACLR in both the SB and the SBLP groups. Differences in IE and varus-valgus rotations were found between the ACL-injured and healthy groups. Conclusion: There were no relevant kinematic differences between SBLP and anatomic SB ACLR during the execution of a single-leg squat. Regardless of the surgical technique, ACLR failed in restoring knee biomechanics. Registration: NCT02323386 (ClinicalTrials.gov identifier). [ABSTRACT FROM AUTHOR]

Background: The burden of anterior cruciate ligament (ACL) injury in professional soccer players is particularly relevant as it represents a potentially career-threatening injury.Hypothesis: Our hypotheses were that (1) injury incidence rate would be similar to that reported in the literature, (2) we would identify a uniform distribution of the injuries along the season, and (3) injury incidence rate would be similar in high-ranked and lower ranked teams, based on final placement in the league.Study Design: Descriptive epidemiological study.Level Of Evidence: Level 4.Methods: Professional male soccer players participating in the Serie A championship league in 7 consecutive seasons (2011-2012 to 2017-2018) were screened to identify ACL injuries through the online football archive transfermarkt.com . Exposure in matches and training were calculated.Results: There were 84 ACL injuries found (mean player age, 25.3 ± 4.2 years). Overall, 25% of ACL injuries were reruptures (15%) or contralateral injuries (10%). ACL incidence rate was 0.4215 per 1000 hours of play during Serie A matches, 0.0305 per 1000 hours of training (rate ratio [RR], 13.8; 95% CI, 8.4-22.7; P < 0.0001), and 0.0618 per 1000 hours of total play. Injury distribution had a bimodal peak, with the highest number of events in October and March. Alternatively, training injuries peaked in June and July. A significantly higher incidence rate was found for the teams ranked from 1st to 4th place compared with those ranked 5th to 20th (0.1256 vs 0.0559 per 1000 hours of play; RR, 2.2; 95% CI, 1.4-3.6; P = 0.0003). A similar finding was found for injury incidence proportion (3.76% vs 1.64%; P = 0.0003).Conclusion: The overall incidence rate of ACL injuries in Italian Serie A was 0.062 per 1000 hours, with a 14-fold risk in matches compared with training. Relevantly, 25% were second injuries. Most injuries occurred in October and March, and an almost 2-fold incidence rate and incidence proportion were noted in those teams ranked in the first 4 positions of the championship league.Clinical Relevance: Knowing the precise epidemiology of ACL injury in one of the most competitive professional football championship leagues could help delineate fields of research aimed to investigate its risk factors. [ABSTRACT FROM AUTHOR]

Background: When anterior cruciate ligament (ACL) reconstruction fails, a revision procedure may be performed to improve knee function, correct instability, and allow return to activities. The results of revision ACL reconstruction have been reported to produce good but inferior patient-reported and objective outcomes compared with primary ACL reconstruction, but the degree to which this is the case varies widely among published studies and may be influenced by heterogeneity of patients, techniques, and endpoints assessed. For those reasons, a systematic review may provide important insights.Questions/purposes: In a systematic review, we asked: (1) What is the proportion of revision ACL reconstruction cumulative failures defined as rerupture or objective failure using prespecified clinical criteria at mean followup of at least 5 years? (2) What are the most common complications of revision ACL reconstruction?Methods: A systematic review was performed by searching PubMed/Medline, EMBASE, and CENTRAL. We included studies that reported the clinical evaluation of revision ACL reconstruction with Lachman test, pivot shift test, side-to-side difference with KT-1000/2000 arthrometer, and with a mean followup of at least 5 years. We excluded studies that incompletely reported these outcomes, that reported only reruptures, or that were not in the English language. Extracted data included the number of graft reruptures and objective clinical failure, defined as a knee that met one of the following endpoints: Lachman test Grade II to III, pivot shift Grade II to III, KT-1000/2000 > 5-mm difference, or International Knee Documentation Committee Grade C or D. For each study, we determined the proportion of patients who had experienced a rupture of the revision ACL graft as well as the proportion of patients who met one or more of our clinical failure endpoints. Those proportions were summed for each study to generate a percentage of patients who met our definition of cumulative failure. Complications and reoperations were recorded but not pooled as a result of inconsistency of reporting and heterogeneity of populations across the included studies. Of the 663 screened studies, 15 articles were included in the systematic review. Because one study reported two separate groups of patients with different treatments, 16 case series were considered in the evaluation.Results: The proportion of reruptures (range, 0%-25%) was > 5% in only four of 16 series and > 10% in only one of them. The objective clinical failures (range, 0%-82%) was > 5% in 15 of 16 series and > 10% in 12 of them. The proportion exceeded 20% in five of 16 series. The cumulative failures (range, 0%-83%) was > 5% in all except one series and > 10% in 12 of 16 series; five series had a cumulative failure proportion > 20%. The most frequent complications were knee stiffness and anterior knee pain, whereas reoperations were primarily débridement and meniscectomies.Conclusions: Considering rerupture alone as a failure endpoint in patients who have undergone revision ACL reconstruction likely underestimates the real failure rate, because the percentage of failures noticeably increases when objective criteria are also considered. Whether patient-reported and subjective scores evaluating knee function, level of activity, satisfaction, and pain might also contribute to the definition of failure may be the focus of future studies.Level Of Evidence: Level IV, therapeutic study. [ABSTRACT FROM AUTHOR]

Purpose of this paper is to provide an overview of the latest research on the anterolateral ligament (ALL) and present the consensus of the ALL Expert Group on the anatomy, radiographic landmarks, biomechanics, clinical and radiographic diagnosis, lesion classification, surgical technique and clinical outcomes. A consensus on controversial subjects surrounding the ALL and anterolateral knee instability has been established based on the opinion of experts, the latest publications on the subject and an exchange of experiences during the ALL Experts Meeting (November 2015, Lyon, France). The ALL is found deep to the iliotibial band. The femoral origin is just posterior and proximal to the lateral epicondyle; the tibial attachment is 21.6 mm posterior to Gerdy's tubercle and 4-10 mm below the tibial joint line. On a lateral radiographic view the femoral origin is located in the postero-inferior quadrant and the tibial attachment is close to the centre of the proximal tibial plateau. Favourable isometry of an ALL reconstruction is seen when the femoral position is proximal and posterior to the lateral epicondyle, with the ALL being tight upon extension and lax upon flexion. The ALL can be visualised on ultrasound, or on T2-weighted coronal MRI scans with proton density fat-suppressed evaluation. The ALL injury is associated with a Segond fracture, and often occurs in conjunction with acute anterior cruciate ligament (ACL) injury. Recognition and repair of the ALL lesions should be considered to improve the control of rotational stability provided by ACL reconstruction. For high-risk patients, a combined ACL and ALL reconstruction improves rotational control and reduces the rate of re-rupture, without increased postoperative complication rates compared to ACL-only reconstruction. In conclusion this paper provides a contemporary consensus on all studied features of the ALL. The findings warrant future research in order to further test these early observations, with the ultimate goal of improving the long-term outcomes of ACL-injured patients. Level of evidence Level V-Expert opinion. [ABSTRACT FROM AUTHOR]

Purpose: Despite the overall success of the surgical anterior cruciate ligament (ACL) reconstruction, some patients still present with instability symptoms even after the surgery, mainly due to the presence of associated lesions. At present, the pivot shift test has been reported to be the benchmark to assess rotatory knee laxity. The purpose of this study was to quantitatively evaluate rotatory knee laxity at time-zero in order to determine whether detected post-reconstruction laxity was predictable by its value measured before the reconstruction, which was hypothized to be influenced by the presence of associated lesions. Methods: Rotatory knee laxity was retrospectively analysed in 42 patients, including two different ACL reconstructions. The maximal anterior displacement and the absolute value of the posterior acceleration reached during the reduction of the tibial lateral compartment were intra-operatively acquired by using a navigation system and identified as discriminating parameters. For each parameter, statistical linear regression analysis (line slope and intercept) was performed between pre- and post-reconstruction values. Results: No statistically significant influence of the initial posterior acceleration on the post-reconstruction outcome was found (line slope, p > 0.05), although a statistically significant line intercept was indeed identified ( p < 0.001). A statistically significant influence on the surgery outcome was instead found for the initial value of the anterior tibial displacement (line slope = 0.39, p = 0.004), meaning that, on average, about 40 % of the post-reconstruction lateral compartment displacement could be explained by the corresponding pre-reconstruction value. Both of these findings highlighted the importance of intra-operative quantification of rotatory knee laxity to identify correct indications for the surgery. Conclusions: This study provided important implications for the future possibility of defining a quantifying tool able to assess rotatory knee laxity during ACL reconstruction. This could allow detection of additional injuries to secondary restraints by easily performing rotatory knee laxity tests, which in turn could reduce post-surgical recurrence of knee instability. [ABSTRACT FROM AUTHOR]

Background: Anterior cruciate ligament (ACL) tear represents a common orthopedic traumatic issue that often leads to an early development of osteoarthritis. To improve the diagnostic and prognostic techniques involved in the assessment of the joint after the trauma and during the healing process, the present work proposes a multi-parametric approach that aims to investigate the relationship between joint function and soft tissue status before and after ACL reconstruction. Methods: Thirteen consecutive patients who underwent ACL reconstruction were preliminarily enrolled in this study. Joint laxity assessment as well as magnetic resonance imaging with T2 mapping were performed in the pre-operative stage, at four and 18 months after surgery to acquire objective information to correlate knee function and soft tissue condition. Results: Correlations were found between graft and cartilage T2 signal, suggesting an interplay between these tissues within the knee joint. Moreover, graft maturation resulted in being connected to joint laxity, as underlined by the correlation between the graft T2 signal and the temporal evolution of knee function. Conclusions: This preliminary study represents a step forward in assessing the effects of ACL graft maturation on knee biomechanics, and vice versa. The presented integrated framework underlines the possibility to quantitatively assess the impact of ACL reconstruction on trauma recovery and cartilage homeostasis. Moreover, the reported findings—despite the preliminary nature of the clinical impacts—evidence the possibility of monitoring the surgery outcomes using a multi-parametric prognostic investigation tool. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate clinical ad radiological outcomes of anterior cruciate ligament (ACL) reconstruction with an immunochemically modified porcine patellar tendon xenograft controlled against human Achilles tendon allograft at 24-month minimum follow-up. Methods: 66 patients undergoing arthroscopic ACL reconstruction were randomized into 2 groups: 34 allografts and 32 xenografts treated to attenuate the host immune response. Follow-up was 24-month minimum. Anterior knee stability was measured as KT − 1000 side-to-side laxity difference (respect to the contralateral healthy knee). Functional performance was assessed by one-legged hop test. Objective manual pivot-shift test and subjective (IKDC, Tegner and SF-36) outcomes were collected. MRI and standard X-Ray were performed. Results: 61 subjects (32 allograft, 29 xenograft) were evaluated at 12 and 24 months. Six of the subjects in xenograft group (20.6%) got an infection attributed to a water-based pathogen graft contamination in processing. Intention-to-treat analysis (using the last observation carried forward imputation method) revealed higher KT − 1000 laxity in xenograft group at 24-month follow-up (P =.042). Also pivot-shift was higher in xenograft group at 12-month (P =.015) and 24-month follow-up (P =.038). Per-protocol analysis (missing/contaminated subjects excluded) did not revealed clinical differences between groups. Tibial tunnel widening in the allograft group was low, whereas xenograft tunnel widening was within the expected range of 20–35% as reported in the literature. No immunological reactivity was associated to xenograft group. Conclusions: High infection rate (20.6%) was reported in xenograft group. Both groups of patients achieved comparable clinical outcomes if missing/contaminated subjects are excluded. Improved harvesting/processing treatments in future studies using xenografts for ACL reconstruction are needed to reduce infection rate, otherwise xenograft should not be used in ACL reconstruction. Level of evidence: Multicenter and double-blinded Randomized Controlled Clinical Trial, Level I. [ABSTRACT FROM AUTHOR]