Future Anterior Cruciate Ligament Research Articles

Knee Biomechanics During Cutting Maneuvers and Secondary ACL Injury Risk: A Prospective Cohort Study of Knee Biomechanics in 756 Female Elite Handball and Soccer Players.

An athlete who returns to sport after an anterior cruciate ligament (ACL) injury has a substantially high risk of sustaining a new secondary ACL injury. Because ACL injuries most frequently occur during cutting maneuvers, such movements should be at the center of research attention. To investigate whether knee biomechanical parameters during side-step cutting maneuvers differ between female elite athletes with and without a history of ACL injury and to evaluate whether such parameters are associated with future secondary ACL injury. Cohort study; Level of evidence, 2. A total of 756 female elite handball and soccer players, of whom 76 had a history of ACL injury, performed a sport-specific cutting task while 3-dimensional kinematics and kinetics were measured. ACL injuries were registered prospectively over an 8-year follow-up period. Seven knee-specific biomechanical variables were the basis for all analyses. Two-way analyses of variance were applied to assess group differences, whereas logistic regression models served to evaluate associations between the knee-specific variables and future secondary ACL injury. When players with a previous ACL injury performed the cutting maneuver with their ipsilateral leg, they exhibited lower knee abduction angles (mean difference [MD], 1.4°-1.5°; 95% CI, 0.2°-2.9°), lower peak knee flexion moments (MD, 0.33 N·m/kg-1; 95% CI, 0.18-0.48 N·m/kg-1), lower peak knee abduction moments (MD, 0.27 N·m/kg-1; 95% CI, 0.12-0.41 N·m/kg-1), and lower peak knee internal rotation moments (MD, 0.06 N·m/kg-1; 95% CI, 0.01-0.12 N·m/kg-1) compared with injury-free players. When players performed the cut with their contralateral leg, no differences were evident (P < .05). None of the 7 knee-specific biomechanical variables was associated with future secondary ACL injury in players with an ACL injury history (P < .05). Approximately 4 years after ACL injury, female elite team-ball athletes still unloaded their ipsilateral knee during cutting maneuvers, yet contralateral knee loading was similar to that of injury-free players. Knee biomechanical characteristics were not associated with future secondary ACL injury.

Human anterior cruciate ligament-derived mesenchymal stem cells for regenerative medicine applications

Background: The anterior cruciate ligament (ACL) has poor healing capabilities and is the most commonly injured knee ligament. Although ACL repair is being highly studied, the current treatment involves reconstructive surgery utilizing autografts or allografts, which have limitations. The use of Mesenchymal Stem Cells (MSCs) as a possible therapeutic option has grown. ACL-derived MSCs are likely to be the best source because studies have shown that target tissue derived stem cells will better differentiate into the target tissue than the stem cells derived from non-target ones. However, the existing literature discusses only the isolation of a mixed population of MSCs. Here we present the isolation, differentiation and characterization of human ACL-derived MSCs according to the International Society for Cellular Therapy (ISCT) criteria.The ACL tissue was enzymatically digested. Separation of MSCs from the crude mixture of cells was then performed by fluorescence activated cell sorting (FACS) analysis. The isolated population were passaged in specific induction medium to differentiate them into adipocyte, osteocytes and chondrocytes. The cells were then further characterized with respect to their growth curve, population doubling time, colony forming ability, anchorage independent growth, and cell surface markers. The cells were finally examined for their tumorigenic potential by cell cycle analysis.Immunoprofiling via FACSs showed an average isolation rate for cells carrying MSCs markers of 5.5%. Cells exhibited spindle-shaped morphology, and immunocytochemistry confirmed the expression of appropriate cell surface markers. The growth curve showed distinct lag and log phase. Over agar assay demonstrated no anchorage independent growth, but clonogenic potential was observed post-culture on plastic Petri dishes. The cells showed a population doubling time of about 1.5 days. Oil Red O, Alizarin Red S, and Alcian Blue staining confirmed adipogenic, osteogenic and chondrogenic differentiation, respectively. Cell cycle analysis displayed more ACL-derived MSCs in G/G phase compared to BMSCs, showing that the isolates were non-tumorigenic. The presence of MSCs within the human ACL was confirmed via ISCT criteria, paving the way for their potential use for future ACL reconstructions. Although BMSCs have been the choice for regenerative purposes, making use of MSCs derived from ACL ligament will cut down the burden of trauma one has to undergo to obtain the Bone Marrow. Moreover, it is more convenient to harvest MSCs from otherwise discarded ACL. Finally, MSCs derived from the target tissue are believed to better differentiate to the ligament tissue than the bone derived MSCs.

What it takes to have a high-grade pivot shift-focus on bony morphology.

Variations in femoral and tibial bony morphology have been associated with higher clinical grading and increased quantitative tibial translation, but not tibial acceleration, during the pivot shift test following anterior cruciate ligament (ACL) injury. The purpose of this study was to determine the impact of femoral and tibial bony morphology, including a measurement influenced by both parameters (the Lateral Tibiofemoral Articular Distance (LTAD)), on the degree of quantitative tibial acceleration during the pivot shift test and rates of future ACL injury. All patients who underwent primary ACL reconstruction from 2014 to 2019 by a senior orthopedic surgeon with available quantitative tibial acceleration data were retrospectively reviewed. All patients underwent a pivot shift examination under anesthesia with a triaxial accelerometer. Measurements of femoral and tibial bony morphology were performed by two fellowship-trained orthopedic surgeons using preoperative magnetic resonance imaging and lateral radiographs. Fifty-one patients were included at a mean follow-up of 4.4years. The mean quantitative tibial acceleration during the pivot shift was 13.8m/s2 (range: 4.9-52.0m/s2). A larger Posterior Condylar Offset Ratio (r = 0.30, p = 0.045), smaller medial-to-lateral width of the medial tibial plateau (r = -0.29, p = 0.041), lateral tibial plateau (r = -0.28, p = 0.042), and lateral femoral condyle (r = -0.29, p = 0.037), and a decreased LTAD (r = -0.53, p < 0.001) significantly correlated with increased tibial acceleration during the pivot shift. Linear regression analysis demonstrated an increase in tibial acceleration of 1.24m/s2 for every 1mm decrease in LTAD. Nine patients (17.6%) sustained ipsilateral graft rupture and 10 patients (19.6%) sustained contralateral ACL rupture. No morphologic measurements were associated with rates of future ACL injury. Increased convexity and smaller bony morphology of the lateral femur and tibia were significantly associated with increased tibial acceleration during the pivot shift. Additionally, a measurement, termed the LTAD, was found to have the strongest association with increased tibial acceleration. Based on the results of this study, surgeons can utilize these measurements to preoperatively identify patients at risk of increased rotatory knee instability. Level IV.

Musculoskeletal pain is not clearly associated with the risk of anterior cruciate ligament reconstruction in adolescents

ObjectivesThe purpose of this study was to investigate whether self-reported musculoskeletal pain (MSP) was associated with a future anterior cruciate ligament reconstruction (ACLR).MethodsIn this population-based prospective cohort study, we included...

Prelanding Knee Kinematics and Landing Kinetics During Single-Leg and Double-Leg Landings in Male and Female Recreational Athletes.

Biomechanical behavior prior to landing likely contributes to anterior cruciate ligament (ACL) injuries during jump-landing tasks. This study examined prelanding knee kinematics and landing ground reaction forces (GRFs) during single-leg and double-leg landings in males and females. Participants performed landings with the dominant leg or both legs while kinematic and GRF data were collected. Single-leg landings demonstrated less time between prelanding minimal knee flexion and initial ground contact, decreased prelanding and early-landing knee flexion angles and velocities, and increased peak vertical and posterior GRFs compared with double-leg landings. Increased prelanding knee flexion velocities and knee flexion excursion correlated with decreased peak posterior GRFs during both double-leg and single-leg landings. No significant differences were observed between males and females. Prelanding knee kinematics may contribute to the increased risk of ACL injuries in single-leg landings compared with double-leg landings. Future studies are encouraged to incorporate prelanding knee mechanics to understand ACL injury mechanisms and predict future ACL injury risks. Studies of the feasibility of increasing prelanding knee flexion are needed to understand the potential role of prelanding kinematics in decreasing ACL injury risk.

Exploring pre-impact landing kinematics associated with increase and decrease in the anterior cruciate ligament injury risk

This study aimed to explore the single-legged landing kinematics that could lead to increase or decrease in the risk of anterior cruciate ligament (ACL) injury. Immediate pre-impact kinematics at the single-legged landing from 33 healthy young female handball players were evaluated. Thereafter, two-year follow-up for ACL injury incidence was conducted, in which six new ACL injuries in non-dominant leg were registered. The evaluation of pre-impact kinematics across participants was performed first by the principal component analysis to decompose them into the kinematic components (KCs), and then by the linear discrimination analysis (LDA) for a set of KC-scores to obtain important KCs for discriminating injured and non-injured legs. The result of LDA showed that the combination of second major KC (knee flexion/extension angle and angular velocity) and some minor KCs such as torso medial/lateral leaning accurately discriminated the injured and non-injured legs with the error rate of 12.5%. To examine the mechanisms of this discriminative ability, we generated hypothetical pre-impact kinematics in the subspaces spanned by eigenvectors of multiple KCs, and examined relationships between pre-impact kinematics and the corresponding knee valgus torque predicted by the motion-equation-based model. The result showed that the second major KC and the minor KCs representing torso medial/lateral leaning and/or hip adduction/abduction angle, which contributed in LDA to discriminating injured legs, also significantly affected the frontal-plane knee loading patterns. These findings suggested that KC-based postural characterization of the pre-impact landing kinematics and the motion-equation-based knee stress quantification possibly explain the future ACL injury risks of female athletes.

Return-to-Sport Criteria After Anterior Cruciate Ligament Reconstruction Fail to Identify the Risk of Second Anterior Cruciate Ligament Injury.

The incidence of second anterior cruciate ligament (ACL) injury after ACL reconstruction (ACLR) is high in young, active populations. Failure to successfully meet return-to-sport (RTS) criteria may identify adult athletes at risk of future injury; however, these studies have yet to assess skeletally mature adolescent athletes. To determine if failure to meet RTS criteria would identify adolescent and young adult athletes at risk for future ACL injury after ACLR and RTS. The tested hypothesis was that the risk of a second ACL injury after RTS would be lower in participants who met all RTS criteria compared with those who failed to meet all criteria before RTS. Prospective case-cohort (prognosis) study. Laboratory. A total of 159 individuals (age = 17.2 ± 2.6 years, males = 47, females = 112). Participants completed an RTS assessment (quadriceps strength, functional hop tests) and the International Knee Documentation Committee patient survey (0 to 100 scale) after ACLR and were then tracked for occurrence of a second ACL tear. Athletes were classified into groups that passed all 6 RTS tests at a criterion level of 90% (or 90 of 100) limb symmetry and were compared with those who failed to meet all criteria. Crude odds ratios and 95% CIs were calculated to determine if passing all 6 RTS measures resulted in a reduced risk of second ACL injury in the first 24 months after RTS. Thirty-five (22%) of the participants sustained a second ACL injury. At the time of RTS, 26% achieved ≥90 on all tests, and the remaining athletes scored less than 90 on at least 1 of the 6 assessments. The second ACL injury incidence did not differ between those who passed all RTS criteria (28.6%) and those who failed at least 1 criterion (19.7%, P = .23). Subgroup analysis by graft type also indicated no differences between groups (P > .05). Current RTS criteria at a 90% threshold did not identify active skeletally mature adolescent and young adult athletes at high risk for second ACL injury.

Descriptive trunk kinematics in healthy collegiate women's soccer players indicate trunk center of mass is laterally positioned prior to decelerating and cutting

ObjectivesTrunk kinematics can contribute to lower extremity biomechanical risk factors for anterior cruciate ligament (ACL) injury. However, normative trunk kinematics during unilateral athletic tasks in a large population of “healthy” (no history of ACL injury and no known future ACL injury) women's soccer players have not been well-described. This study's purposes were to describe trunk kinematics in a population of 37 healthy collegiate women's soccer players completing a step-down, a deceleration, and a 90° cut, and to provide a reference for normative values. MethodsA cross-sectional cohort of 37 female soccer players were analysed for this study. Trunk forward flexion and lateral flexion were measured relative to the pelvis, and trunk centre of mass position was measured relative to the proximal tibia. Trunk kinematics were characterized by individual values at key events during the tasks and time-series curves normalized to 100% of the time. ResultsParticipants demonstrated increasing trunk forward flexion with increasing knee flexion angle, small amounts of increasing ipsilateral trunk flexion with increasing peak knee abduction moment, and trunk centre of mass position that moved medially during the deceleration and cut tasks. Additionally, participants demonstrated peak trunk lateral flexion angles milliseconds before peak knee flexion angle. ConclusionThis study provides a reference for identifying aberrant trunk mechanics that may increase the risk for non-contact ACL injury. Level of evidenceLevel II.

Strength and Biomechanical Risk Factors for Noncontact ACL Injury in Elite Female Footballers: A Prospective Study.

This study aimed to determine if a preseason field-based test battery was prospectively associated with noncontact anterior cruciate ligament (ACL) injury in elite female footballers. In total, 322 elite senior and junior female Australian Rules Football and soccer players had their isometric hip adductor and abductor strength, eccentric knee flexor strength, countermovement jump (CMJ) kinetics, and single-leg hop kinematics assessed during the 2019 preseason. Demographic and injury history details were also collected. Footballers were subsequently followed for 18 months for ACL injury. Fifteen noncontact ACL injuries occurred during the follow-up period. Prior ACL injury (odds ratio [OR], 9.68; 95% confidence interval (95% CI), 2.67-31.46), a lower isometric hip adductor to abductor strength ratio (OR, 1.98; 95% CI, 1.09-3.61), greater CMJ peak take-off force (OR, 1.74; 95% CI, 1.09-3.61), and greater single-leg triple vertical hop average dynamic knee valgus (OR, 1.97; 95% CI, 1.06-3.63) and ipsilateral trunk flexion (OR, 1.60; 95% CI, 1.01-2.55) were independently associated with an increased risk of subsequent ACL injury. A multivariable prediction model consisting of CMJ peak take-off force, dynamic knee valgus, and ACL injury history that was internally validated classified ACL injured from uninjured footballers with 78% total accuracy. Between-leg asymmetry in lower limb strength and CMJ kinetics were not associated with subsequent ACL injury risk. Preseason field-based measures of lower limb muscle strength and biomechanics were associated with future noncontact ACL injury in elite female footballers. These risk factors can be used to guide ACL injury screening practices and inform the design of targeted injury prevention training in elite female footballers.

ACL Rehabilitation: How Can We Lessen Injury Rates?

Rehabilitation is commonly used following anterior cruciate ligament (ACL) injury, though specific protocols are widely varied. Regardless of whether the injury is managed operatively or nonoperatively, quadriceps strengthening and return to full range of motion are the main focus points of rehabilitation, both to regain function and prevent future injury. Preoperative ACL rehabilitation has been shown to improve clinical outcomes. Home exercise programs can also provide good clinical outcomes when compared to traditional in-person physical therapy. A multitude of specific modalities (bracing, functional testing, neuromuscular training, electrostimulation, cryotherapy, and blood flow restriction therapy) may also provide benefit in ACL rehabilitation. Analysis of biomechanics during rehabilitation allows for customization of rehabilitation approaches, provides insight on muscular deficiencies, and helps ACL-injured patients re-establish functionality with the goal of preventing future ipsilateral or contralateral injury. Given the lack of consensus on rehabilitation protocols following ACL injury, the purpose of this review was to examine the efficacy of a variety of protocols and specific modalities and discuss their roles in the prevention of future ACL injury.

Asymmetries in Dynamic Valgus Index After Anterior Cruciate Ligament Reconstruction: A Proof-of-Concept Study.

Individuals with anterior cruciate ligament reconstruction (ACLR) are at a higher risk for subsequent anterior cruciate ligament (ACL) tears. Risk factors for ACL injuries likely involve a combination of anatomical, biomechanical, and neuromuscular factors. Dynamic knee valgus has been indicated as a possible biomechanical factor for future ACL injuries. Given that knee valgus is often accompanied by contralateral pelvic drop during single-leg activities, a dynamic valgus index (DVI) that quantifies combined kinematics of the knee and hip in the frontal plane has recently been developed. As the premise of asymmetrical DVI between limbs in the ACLR population has not been examined, this cross-sectional study was conducted with the aim to compare DVI between individuals with ACLR and healthy controls. Videos were taken for 12 participants with ACLR and 20 healthy controls when they performed single-leg hopping. One-way ANOVA revealed a higher DVI in the injured limb of the ACLR group when compared to their non-injured limb and to the healthy limb of the control group. As our data showed increased DVI in the injured limb of the ACLR group, the DVI approach accounting for hip and knee kinematics may be used to identify frontal plane movement deficits during single-leg hopping in individuals with ACLR.

Risk of Anterior Cruciate Ligament Injury in Female Soccer Athletes: A Review

Soccer is becoming an increasingly popular sport amongst women. Common movements during play, such as jumping and cutting, require rapid acceleration and deceleration of multiple lower-limb joints. The anterior cruciate ligament (ACL), which contributes to stabilization of the knee, is often injured during these events. ACL injury typically requires costly surgery, extended time away from sports, and jeopardizes long-term joint health. Due to sex-specific factors such as menstruation and anatomical disadvantages, women are more susceptible to tearing their ACL. Injury often occurs in non-contact scenarios during rapid acceleration or deceleration movements. Research has examined these movements and established several kinematic and kinetic mechanisms as well as muscle activation patterns that frequently occur at the time of injury, however results tend to vary based on population. This article summarizes recent and relevant literature of ACL injury mechanisms and highlights the lack of specific research in the high-risk female soccer athlete population. Due to inconclusive risk factors, injury prevention programs within this population have been inconsistent. ACL injury risk for female soccer athletes should be closer examined so that more specific injury risks can be established, and effective protective measures can be taken. Raised awareness of this need may capture attention in the research and medical communities and potentially stimulate the development of strategies that limit future ACL injury and thus the challenges it brings to the high-risk female soccer athlete.

Risk of Anterior Cruciate Ligament Injury in Female Soccer Athletes: A Review

Soccer is becoming an increasingly popular sport amongst women. Common movements during play, such as jumping and cutting, require rapid acceleration and deceleration of multiple lower-limb joints. The anterior cruciate ligament (ACL), which contributes to stabilization of the knee, is often injured during these events. ACL injury typically requires costly surgery, extended time away from sports, and jeopardizes long-term joint health. Due to sex-specific factors such as menstruation and anatomical disadvantages, women are more susceptible to tearing their ACL. Injury often occurs in non-contact scenarios during rapid acceleration or deceleration movements. Research has examined these movements and established several kinematic and kinetic mechanisms as well as muscle activation patterns that frequently occur at the time of injury, however results tend to vary based on population. This article summarizes recent and relevant literature of ACL injury mechanisms and highlights the lack of specific research in the high-risk female soccer athlete population. Due to inconclusive risk factors, injury prevention programs within this population have been inconsistent. ACL injury risk for female soccer athletes should be closer examined so that more specific injury risks can be established, and effective protective measures can be taken. Raised awareness of this need may capture attention in the research and medical communities and potentially stimulate the development of strategies that limit future ACL injury and thus the challenges it brings to the high-risk female soccer athlete.

Kiss goodbye to the ‘kissing knees’: no association between frontal plane inward knee motion and risk of future non-contact ACL injury in elite female athletes

ABSTRACT The aim of this study was to investigate if frontal plane knee and hip control in single-leg squats or vertical drop jumps with an overhead target were associated with future non-contact anterior cruciate ligament (ACL) injury in elite female athletes. Of the 429 handball and 451 football athletes (age 21.5 ± 4.0 years, height 169.6 ± 6.4 cm, body weight 67.1 ± 8.0 kg), 722 non-injured and 56 non-contact ACL injured participants were eligible for analysis. We calculated lateral pelvic tilt, frontal plane knee projection angle, medial knee position, and side-to-side asymmetry in these from 2D videos recorded at baseline, and recorded any new ACL injuries prospectively. None of the aforementioned variables in either screening task were different or could discriminate between injured and non-injured athletes (all p values >.05 and Cohen’s d values < .27). Two-dimensional video assessment of frontal plane knee and hip control during both a single-leg squat and vertical drop jump was unable to identify individuals at increased risk of non-contact ACL injury, thus should not be used for screening.

Poor Validity of Functional Performance Tests to Predict Knee Injury in Female Soccer Players With or Without Anterior Cruciate Ligament Reconstruction

Background: Various tests have been developed to evaluate athletes’ functional performance and for use as screening tools for injury prediction. Further validation of their accuracy to predict injury is needed. Purpose: To investigate the validity of predetermined cutoffs used to differentiate between high- and low-risk players in different functional performance tests to predict (1) anterior cruciate ligament (ACL) injury or (2) severe traumatic knee injury in a cohort of female soccer players with a primary unilateral ACL reconstruction and a cohort of knee-healthy players. Study Design: Cohort study; Level of evidence, 2. Methods: A total of 117 active female soccer players (mean age ± SD, 20 ± 2 years) an average of 19 ± 9 months after ACL reconstruction and 119 knee-healthy players (age, 19 ± 3 years) were prospectively followed up for 2 years for new knee injuries. At baseline, all players underwent tests to assess postural control (Star Excursion Balance Test), hop performance (single-leg hop for distance, side hop), and movement asymmetries in the lower limbs and trunk (drop vertical jump [DVJ], tuck jump). The predictive validity of the test cutoffs to identify players who would sustain an ACL injury or a severe traumatic knee injury (absence from soccer play, >28 days) was assessed. The risk ratio (RR), area under the receiver operating characteristic curve (AUC), sensitivity, and specificity were calculated. Results: A total of 46 players (39%) with ACL reconstruction sustained 48 severe knee injuries, including 28 ACL ruptures. Of the knee-healthy players, 13 (11%) sustained 14 severe knee injuries, including 8 ACL ruptures. No association was found between the predetermined functional performance test cutoffs and the risk of a new ACL injury or severe knee injury in players with ACL reconstruction. In knee-healthy players, the only variable associated with future ACL injury was ≥6.5 cm knee valgus in the frontal plane (any knee) in the DVJ (RR, 4.93; 95% CI, 1.04-23.40; P = .045), but with only fair predictive validity (AUC, 0.7; sensitivity, 0.75; specificity, 0.65). Conclusion: In our cohorts of female soccer players, the validity of commonly used functional performance tests to predict new knee injuries was poor. Only knee valgus during the DVJ was associated with new ACL injuries in knee-healthy players, but with only fair predictive validity.

Does delayed onset muscle soreness affect the biomechanical variables of the drop vertical jump that have been associated with increased ACL injury risk? A randomised control trial.

Delayed onset muscle soreness (DOMS) and Anterior Cruciate Ligament (ACL) injuries are both prevalent in sport. It is currently unknown whether DOMS increases ACL injury risk. This study aimed to provide preliminary insight on whether DOMS affects ACL injury risk by investigating whether DOMS affects the biomechanical variables of the DVJ that have been identified as risk factors for future ACL injury. This was a randomised control trial involving 32 active individuals aged 18-35years, with no history of ACL injury. Participants underwent two sessions of force-plate testing and 3D motion analysis of the drop vertical jump (DVJ). The DVJ was chosen as it has been investigated prospectively for association with future ACL injury. Initial testing was followed by randomisation to DOMS or control group. The DOMS group underwent a DOMS-inducing exercise protocol, the control group did not. Both groups were re-tested 48h after initial testing. Five variables of the DVJ that have been associated with future ACL injury were chosen for analysis - peak knee flexion angle, peak vertical ground reaction force, ground contact time, peak knee abduction angle & peak knee abduction moment. Between-group differences were compared using a two-way mixed analysis of variance; alpha level set to 0.05. DOMS was successfully induced in all participants of the DOMS group however no statistically significant group x time interactions were found for any of the five variables analysed. DOMS did not affect the biomechanical variables of the DVJ that have been associated with future ACL injury. By extension, this may suggest that DOMS might not affect ACL injury risk. However, it is also possible that certain attributes of the DVJ meant that any effect of DOMS was simply unable to be quantified, even if an effect existed. All considered, our position is that conclusion cannot be drawn from this study alone on whether DOMS affects ACL injury risk. Further research is required.

Can Biomechanical Testing After Anterior Cruciate Ligament Reconstruction Identify Athletes at Risk for Subsequent ACL Injury to the Contralateral Uninjured Limb?

Background: Athletes are twice as likely to rupture the anterior cruciate ligament (ACL) on their healthy contralateral knee than the reconstructed graft after ACL reconstruction (ACLR). Although physical testing is commonly used after ACLR to assess injury risk to the operated knee, strength, jump, and change-of-direction performance and biomechanical measures have not been examined in those who go on to experience a contralateral ACL injury, to identify factors that may be associated with injury risk. Purpose: To prospectively examine differences in biomechanical and clinical performance measures in male athletes 9 months after ACLR between those who ruptured their previously uninjured contralateral ACL and those who did not at 2-year follow-up and to examine the ability of these differences to predict contralateral ACL injury. Study Design: Case-control study; Level of evidence, 3. Methods: A cohort of male athletes returning to level 1 sports after ACLR (N = 1045) underwent isokinetic strength testing and 3-dimensional biomechanical analysis of jump and change-of-direction tests 9 months after surgery. Participants were followed up at 2 years regarding return to play or at second ACL injury. Between-group differences were analyzed in patient-reported outcomes, performance measures, and 3-dimensional biomechanics for the contralateral limb and asymmetry. Logistic regression was applied to determine the ability of identified differences to predict contralateral ACL injury. Results: Of the cohort, 993 had follow-up at 2 years (95%), with 67 experiencing a contralateral ACL injury and 38 an ipsilateral injury. Male athletes who had a contralateral ACL injury had lower quadriceps strength and biomechanical differences on the contralateral limb during double- and single-leg drop jump tests as compared with those who did not experience an injury. Differences were related primarily to deficits in sagittal plane mechanics and plyometric ability on the contralateral side. These variables could explain group membership with fair to good ability (area under the curve, 0.74-0.80). Patient-reported outcomes, limb symmetry of clinical performance measures, and biomechanical measures in change-of-direction tasks did not differentiate those at risk for contralateral injury. Conclusion: This study highlights the importance of sagittal plane control during drop jump tasks and the limited utility of limb symmetry in performance and biomechanical measures when assessing future contralateral ACL injury risk in male athletes. Targeting the identified differences in quadriceps strength and plyometric ability during late-stage rehabilitation and testing may reduce ACL injury risk in healthy limbs in male athletes playing level 1 sports. Clinical Relevance: This study highlights the importance of assessing the contralateral limb after ACLR and identifies biomechanical differences, particularly in the sagittal plane in drop jump tasks, that may be associated with injury to this limb. These factors could be targeted during assessment and rehabilitation with additional quadriceps strengthening and plyometric exercises after ACLR to potentially reduce the high risk of injury to the previously healthy knee. Registration: NCT02771548 (ClinicalTrials.gov identifier).

Reduced 2-D Frontal Plane Motion During Single-Limb Landing Is Associated With Risk of Future Anterior Cruciate Ligament Graft Rupture After Anterior Cruciate Ligament Reconstruction and Return to Sport: A Pilot Study.

To evaluate the association between 2-D frontal plane movement and second anterior cruciate ligament (ACL) injury risk in young athletes at return to sport (RTS) after ACL reconstruction. Prospective cohort. Forty-nine participants who had ACL reconstruction (mean ± SD age, 16.5 ± 3.0 years) performed a single-leg drop landing from a 31-cm box at the time of their RTS. Frontal plane trunk, pelvis, and knee angles were measured using 2-D video analysis at the point of maximum depth during landing. Summated frontal plane angles were calculated by adding trunk, pelvis, and knee angles. Participants were grouped based on whether or not they sustained an ACL graft rupture over the 24 months after RTS. Seven participants (14%) sustained an ipsilateral graft rupture within 24 months after RTS. Participants who suffered a second ACL injury had a significant reduction in the summated frontal plane angle of the trunk, pelvis, and knee (P = .018) and of the trunk and knee (P = .02) compared to those who did not suffer a second injury. For every 5° increase in the summated trunk, pelvis, and knee angle (odds ratio [OR] = 0.54; 95% confidence interval [CI]: 0.31, 0.94) and the summated trunk and knee angle (OR = 0.48; 95% CI: 0.25, 0.94), the athletes were 46% to 52% less likely to sustain a graft rupture. Athletes who suffered an ACL graft rupture within 24 months of RTS had a more rigid posture when landing compared to their uninjured peers. The results of this pilot study should be replicated in a larger sample to determine whether this method has merit as a screening tool to identify athletes at high risk for second ACL injury. J Orthop Sports Phys Ther 2021;51(2):82-87. Epub 25 Dec 2020. doi:10.2519/jospt.2021.9302.

Return to Play Following Isolated and Combined Anterior Cruciate Ligament Reconstruction: 25+ Years of Experience Treating National Football League Athletes.

Background:The first case series to report on return to play (RTP) in National Football League (NFL) players after primary anterior cruciate ligament (ACL) reconstruction (ACLR) published an RTP rate of 63%. Other studies that have attempted to estimate RTP after ACLR in these elite athletes have been largely based on secondary sources. This study is the second to report the authors’ own results in treating ACL injuries in NFL players spanning a study period of 25+ years.Purpose:To report the senior authors’ experience treating ACL injuries in NFL players as well as revisit the concept of RTP as it is currently used to measure successful surgical outcomes in professional athletes.Study Design:Case series; Level of evidence, 4.Methods:A total of 47 NFL players were treated at our institution for knee injuries that included a complete tear of the ACL; of these, 41 were primary ACLR and 6 were revision ACLR. Of the primary ACLRs, 6 were classified as ACL plus additional ligament and 3 were classified as multiligament. Return to game play (RTGP) was defined as returning to play in a regular-season game. Successful return to previous participation (RTPP) was defined as return to a level of participation equal to the level the player had reached before injury. Multivariate analysis was used to assess predictors of successful RTPP.Results:Using the RTGP criteria proposed by prior authors, the RTGP after primary ACLR was 73%. Using our proposed RTPP criteria, 87.8% of players successfully returned to the same level of participation after primary ACLR. RTGP percentage for all NFL players after ACLR (including multiligament injuries) was 67.6%, and the overall RTPP for those patients was 87.8%. In multivariate analysis, age ≤25 years was predictive of successful RTPP. High draft picks and offensive players played more seasons after primary ACLR. ACL graft rupture occurred in 4.3% of this cohort. Contralateral ACL tear occurred in 8.5%.Conclusion:Regardless of which definition is used to measure a successful outcome after ACLR surgery, the findings of this study suggest that successful return after primary ACLR in NFL athletes is higher than previously reported. While concomitant reconstruction of a single collateral ligament did not affect RTPP, revision ACLR or bicruciate plus collateral ligament reconstruction was associated with a lower RTPP rate. Age ≤25 years predicted successful RTPP. The risk of a future ACL tear of either knee after index reconstruction was approximately 13%.

Do knee abduction kinematics and kinetics predict future anterior cruciate ligament injury risk? A systematic review and meta-analysis of prospective studies

BackgroundTo systematically review the association between knee abduction kinematics and kinetics during weight-bearing activities at baseline and the risk of future anterior cruciate ligament (ACL) injury.MethodsSystematic review and meta-analysis according to PRISMA guidelines. A search in the databases MEDLINE (PubMed), CINAHL, EMBASE and Scopus was performed. Inclusion criteria were prospective studies including people of any age, assessing baseline knee abduction kinematics and/or kinetics during any weight-bearing activity for the lower extremity in individuals sustaining a future ACL injury and in those who did not.ResultsNine articles were included in this review. Neither 3D knee abduction angle at initial contact (Mean diff: -1.68, 95%CI: − 4.49 to 1.14, ACL injury n = 66, controls n = 1369), peak 3D knee abduction angle (Mean diff: -2.17, 95%CI: − 7.22 to 2.89, ACL injury n = 25, controls n = 563), 2D peak knee abduction angle (Mean diff: -3.25, 95%CI: − 9.86 to 3.36, ACL injury n = 8, controls n = 302), 2D medial knee displacement (cm; Mean diff:: -0.19, 95%CI: − 0,96 to 0.38, ACL injury n = 72, controls n = 967) or peak knee abduction moment (Mean diff:-10.61, 95%CI: - 26.73 to 5.50, ACL injury n = 54, controls n = 1330) predicted future ACL injury.ConclusionContrary to clinical opinion, our findings indicate that knee abduction kinematics and kinetics during weight-bearing activities may not be risk factors for future ACL injury. Knee abduction of greater magnitude than that observed in the included studies as well as factors other than knee abduction angle or moment, as possible screening measures for knee injury risk should be evaluated in future studies.