Search

Following anterior cruciate ligament reconstruction (ACLR), patients exhibit abnormal walking mechanics and quadriceps dysfunction. Quadriceps dysfunction has been largely attributed to muscle atrophy and weakness. While important, these factors do not capture intrinsic properties of muscle that govern its ability to generate force and withstand load. While fascicle abnormalities after ACLR have been documented in early stages of recovery (<12 mo), long-term effects of ACLR on fascicle mechanics remain unexplored. We evaluated quadriceps fascicle mechanics during walking 3 years post-ACLR and examined the relationship with knee mechanics. Participants included 24 individuals with ACLR and 24 Controls. Linear mixed models compared the ACLR, Contralateral, and Controls limbs for (1) quadriceps strength, (2) fascicle architecture and mechanics, and (3) knee mechanics. No difference in strength or overall fascicle length excursions was found between limbs. The ACLR limb exhibited longer fascicles at heel strike and peak knee extension moment (P <.001–.004), and smaller fascicle angles at heel strike, peak knee extension moment, and overall suppressed fascicle angle excursions (P <.001–.049) relative to the Contralateral and/or Control limb. This indicates an abnormality in fascicle architecture and mechanics following ACLR and suggests abnormalities in contractile function that cannot be explained by muscle weakness and may contribute to long-term gait irregularities. [ABSTRACT FROM AUTHOR]

Background: Biomechanical knee asymmetry is commonly present after anterior cruciate ligament (ACL) reconstruction. Factors that could assist in identification of asymmetrical biomechanics after ACL reconstruction could help clinicians in making return-to-play decisions. The purpose of this study is to determine factors that may contribute to knee biomechanical asymmetry present after ACL reconstruction. Hypothesis: We hypothesized that quadriceps strength and activation and patient-reported function would allow for identification of patients with symmetrical knee biomechanics. Study Design: Cross-sectional study. Level of Evidence: Level 3. Methods: Thirty-one subjects (18 women; time since ACL reconstruction = 284.4 ± 53.6 days) who underwent ACL reconstruction and were to return to activity were recruited. Participants completed bilateral assessments of isokinetic quadriceps strength, quadriceps activation using the superimposed burst technique, and biomechanical function testing during a single-leg forward hop. The International Knee Documentation Committee (IKDC) subjective knee form was also completed. Symmetry values were calculated for each variable. Decision trees were utilized to determine which input factors (quadriceps strength symmetry, quadriceps activation symmetry, IKDC score, age, sex, height, mass, graft type) were able to identify participants who had symmetrical knee flexion angles (KFAs) and extension moments. Angles and moments were considered symmetrical if symmetry values were ≥90%. Results: Quadriceps strength and activation symmetry were able to predict whether a patient landed with symmetrical or asymmetrical KFAs, with thresholds of 77.2% strength symmetry and 91.3% activation symmetry being established. Patient-reported function and quadriceps strength were factors that allowed for classification of participants with symmetrical/asymmetrical knee extension moments, with thresholds of 89.1 for the IKDC and 80.0% for quadriceps strength symmetry. Conclusions: Quadriceps strength contributed to both models and appears to be a critical factor for achieving symmetrical knee biomechanics. High patient-reported function and quadriceps activation are also important for restoring knee biomechanical symmetry after ACL reconstruction. Clinical Relevance: Quadriceps strength and activation and patient-reported function may be able to assist clinicians in identifying ACL patients with symmetrical/asymmetrical knee biomechanics. [ABSTRACT FROM AUTHOR]

Background: Thigh muscle weakness after anterior cruciate ligament reconstruction (ACLR) can persist after returning to activity. While resistance training can improve muscle function, "nonfunctional" training methods are not optimal for inducing transfer of benefits to activities such as walking. Here, we tested the feasibility of a novel functional resistance training (FRT) approach to restore strength and function in an individual with ACLR. Hypothesis: FRT would improve knee strength and function after ACLR. Study Design: Case report. Level of Evidence: Level 5. Methods: A 15-year-old male patient volunteered for an 8-week intervention where he performed 30 minutes of treadmill walking, 3 times per week, while wearing a custom-designed knee brace that provided resistance to the thigh muscles of his ACLR leg. Thigh strength, gait mechanics, and corticospinal and spinal excitability were assessed before and immediately after the 8-week intervention. Voluntary muscle activation was evaluated immediately after the intervention. Results: Knee extensor and flexor strength increased in the ACLR leg from pre- to posttraining (130 to 225 N·m [+74%] and 44 to 88 N·m [+99%], respectively) and increases in between-limb extensor and flexor strength symmetry (45% to 92% [+74%] and 47% to 72% [+65%], respectively) were also noted. After the intervention, voluntary muscle activation in the ACLR leg was 72%, compared with the non-ACLR leg at 75%. Knee angle and moment during late stance phase decreased (ie, improved) in the ACLR leg and appeared more similar to the non-ACLR leg after FRT training (18° to 14° [−23.4] and 0.07 to −0.02 N·m·kg−1·m−1 [−122.8%], respectively). Corticospinal and spinal excitability in the ACLR leg decreased (3511 to 2511 [−28.5%] and 0.42 to 0.24 [−43.7%], respectively) from pre- to posttraining. Conclusion: A full 8 weeks of FRT that targeted both quadriceps and hamstring muscles lead to improvements in strength and gait, suggesting that FRT may constitute a promising and practical alternative to traditional methods of resistance training. Clinical Relevance: FRT may serve as a viable approach to improve knee strength and function after ACL reconstruction. [ABSTRACT FROM AUTHOR]

The purpose of this study was to examine the combined impact of experience and decision making on frontal plane knee joint biomechanics during a cutting maneuver. Kinematic and kinetic data were collected from 12 recreationally active and 18 NCAA Division I female athletes during execution of anticipated and unanticipated single-leg land-and-cut maneuvers. Knee joint abduction angles and external knee joint abduction torques were calculated and discrete peak stance-phase variables were extracted. Angle and torque time-series data were also submitted to separate functional data analyses. Variables derived from the functional data analyses indicated that decision making influenced knee abduction angle and torque time series in the recreational group only. Specifically, these variables pointed to greater knee abduction at the end of stance as well as a greater, albeit delayed peak in knee abduction torque at the beginning of landing in the recreational athletes during the unanticipated condition. In addition, the recreational athletes displayed greater discrete peak knee abduction angles than the Division I athletes regardless of condition. Discrete peak knee abduction torque did not differ between groups or conditions. [ABSTRACT FROM AUTHOR]

Objective Restoring quadriceps muscle strength following anterior cruciate ligament reconstruction (ACLR) may prevent the posttraumatic osteoarthritis that affects over 50% of knees with ACLR. However, a fundamental gap exists in our understanding of how to maximize muscle strength through rehabilitation. Neurological deficits and muscle atrophy are 2 of the leading mechanisms of muscle weakness after ACLR. High-intensity neuromuscular electrical stimulation (NMES) and eccentric exercise (ECC) have been shown to independently target these mechanisms. If delivered in succession, NMES and then ECC may be able to significantly improve strength recovery. The objectives of this study were to evaluate the ability of NMES combined with ECC to restore quadriceps strength and biomechanical symmetry and maintain cartilage health at 9 and 18 months after ACLR. Methods This study is a randomized, double-blind, placebo-controlled, single-center clinical trial conducted at the University of Michigan. A total of 112 participants between the ages of 14 and 45 years and with an anterior cruciate ligament rupture will be included. Participants will be randomly assigned 1:1 to NMES combined with ECC or NMES placebo combined with ECC placebo. NMES or NMES placebo will be delivered 2 times per week for 8 weeks beginning 10 to 14 days postoperatively and will be directly followed by 8 weeks of ECC or ECC placebo delivered 2 times per week. The co-primary endpoints are change from baseline to 9 months and change from baseline to 18 months after ACLR in isokinetic quadriceps strength symmetry. Secondary outcome measures include isometric quadriceps strength, quadriceps activation, quadriceps muscle morphology (cross-sectional area), knee biomechanics (sagittal plane knee angles and moments), indexes of patient-reported function, and cartilage health (T1ρ and T2 relaxation time mapping on magnetic resonance imaging). Impact The findings from this study might identify an intervention capable of targeting the lingering quadriceps weakness after ACLR and in turn prevent deterioration in cartilage health after ACLR, thereby potentially improving function in this patient population. [ABSTRACT FROM AUTHOR]

Context: Patients who undergo anterior cruciate ligament reconstruction (ACLR) present with strength and biomechanical deficits at return to activity (RTA). Deficits in strength and biomechanical symmetry impair function during activity and may predispose patients to subsequent injury. Objective: To compare strength and biomechanical function in patients with ACLR at RTA and more than 12 months post-ACLR. Design: Descriptive laboratory study. Setting: Research laboratory. Patients or Other Participants: A total of 20 participants (12 females, 8 males; age = 21.40 ± 5.60 years, height = 171.3 ± 10.2 cm, mass = 73.21 ± 19.41 kg) who had undergone ACLR and were cleared to RTA were recruited. Intervention(s): Strength was measured during knee extension and evaluated by the isometric and isokinetic quadriceps index. Biomechanical function was evaluated using symmetry values for sagittal-plane knee-joint rotations, changes in sagittal-plane knee-joint rotation, knee-extension moments, and changes in knee-extension moment that were recorded during a single-legged forward hop. Main Outcome Measure(s): Self-reported function was measured using the International Knee Documentation Committee Subjective Knee Evaluation Form. Participants were assessed at RTA (212.25 ± 28.11 days) and more than 12 months post-ACLR (556.25 ± 230.89 days). Results: At RTA, strength and biomechanical values were less than 80% symmetric. We observed improvements from RTA to more than 12 months post-ACLR for the isometric quadriceps index (F1,18 = 29.22, P < .001), isokinetic quadriceps index (F1,18 = 10.88, P = .004), sagittal-plane knee-joint rotations (F1,19 = 9.58, P = .006), change in sagittal-plane knee-joint rotations (F1,19 = 7.83, P = .01), knee-extension moments (F1,19 = 5.73, P = .03), change in knee-extension moments (F1,19 = 21.10, P < .001), and self-perceived function (F1,19 = 11.50, P = .003). Of the 7 variables that showed improvement at more than 12 months post-ACLR, only 3 met the recommended criteria (≥90%). Conclusions: Patients with ACLR showed asymmetry in strength and biomechanics at RTA. These asymmetries, along with self-perceived function, improved over time. However, despite improvements in strength and biomechanics at RTA, asymmetries of more than 10% were still present more than 12 months post-ACLR. [ABSTRACT FROM AUTHOR]

Context: Lateral subchondral bone bruises (BBs) occur frequently with anterior cruciate ligament (ACL) injuries. These BBs are associated with pain during weight bearing, leading individuals to increase medial tibiofemoral loading to alleviate pain laterally. Increased medial tibiofemoral loading may precipitate the development or progression of posttraumatic osteoarthritis; however, no in vivo biomechanical data exist to confirm that lateral BBs increase medial tibiofemoral loading as measured by the external knee-adduction moment (KAM). Objective: To determine whether lateral BBs after ACL injury increase the external KAM during walking. Design: Descriptive laboratory study. Design: Descriptive laboratory study. Patients or Other Participants: Eleven volunteers with an ACL injury (age = 20.36 ± 4.03 years, height = 177.60 ± 8.59 cm, mass = 79.70 ± 16.33 kg), 12 with an ACL injury and a lateral BB (ACL + BB; age = 19.25 ± 5.58 years, height = 170.71 ± 9.40 cm, mass = 66.79 ± 11.91 kg), and 12 healthy controls (age = 19.67 ± 5.19 years, height = 173.29 ± 11.58 cm, mass = 67.07 ± 11.25 kg) participated. Intervention(s): We recorded peak KAM during 3 walking trials (1.1 ± 0.6 m/s) in which participants walked over a force platform located in the field of view of a motion-capture system. 0.14 ± 0.07 Nmkg-1m-1, ACL + BB = 0.21 ± 0.08 Nmkg-1m-1, control = 0.20 ± 0.08 Nm kg-1m-1; F2,35 = 3.243, P = .052). Knee-pain frequency and severity were greater in the ACL-injury (frequency = 2.55 ± 1.81, severity = 3.36 ± 1.75; both P < .001) and ACL + BB (frequency = 3.58 ± 2.81, severity = 4.08 ± 3.20; both P < .001) groups than in the control group (frequency = 0.00 ± 0.00, severity = 0.00 ± 0.00). Knee function was greater in the control group (100.00 ± 0.00) than in the ACL-injury (59.35 ± 17.31; P < .001) and ACL + BB (46.46 ± 25.85; P < .001) groups. Conclusions: The ACL + BB groups did not walk with a greater external KAM than the ACL-injury or control groups. Thus, lateral tibiofemoral BB did not influence knee frontal-plane loading after ACL injury. [ABSTRACT FROM AUTHOR]

Background: Quadriceps strength deficits are observed clinically after anterior cruciate ligament (ACL) injury and reconstruction and are often not overcome despite rehabilitation. Given that quadriceps strength may be important for achieving symmetrical joint biomechanics and promoting long-term joint health, determining the magnitude of strength deficits that lead to altered mechanics is critical. Purpose: To determine if the magnitude of quadriceps strength asymmetry alters knee and hip biomechanical symmetry as well as functional performance and self-reported function. Study Design: Cross-sectional study; Level of evidence, 3. Methods: A total of 73 patients were tested at the time they were cleared for return to activity after ACL reconstruction. Quadriceps strength and activation, scores on the International Knee Documentation Committee form, the hop for distance test, and sagittal plane lower extremity biomechanics were recorded while patients completed a single-legged hop. Results: Patients with high and moderate quadriceps strength symmetry had larger central activation ratios as well as greater limb symmetry indices on the hop for distance compared with patients with low quadriceps strength symmetry (P < .05). Similarly, knee flexion angle and external moment symmetry were higher in the patients with high and moderate quadriceps symmetry compared with those with low symmetry (P < .05). Quadriceps strength was found to be associated with sagittal plane knee angle and moment symmetry (P < .05). Conclusion: Patients with low quadriceps strength displayed greater movement asymmetries at the knee in the sagittal plane. Quadriceps strength was related to movement asymmetries and functional performance. Rehabilitation after ACL reconstruction needs to focus on maximizing quadriceps strength, which likely will lead to more symmetrical knee biomechanics. [ABSTRACT FROM AUTHOR]

The article reports on research which was conducted to investigate the comparative adaptations of lower limb biomechanics during unilateral and bilateral landings after different neuromuscular-based anterior cruciate ligament injury prevention protocols. Researchers evaluated the lower limb biomechanics of 43 female subjects during unilateral and bilateral landings immediately before and after a six-week neuromuscular training program or no training program. They found that plyometric training led to signifcant biomechanical changes but concluded that the changes may not be evident in all landing types.

Abstract: Background : Biomechanical variability during movement may influence joint stability in individuals with chronic ankle instability (CAI). The purpose of this study was to compare the kinematic and the kinetic inter-trial variability between healthy and CAI individuals. Methods : Eleven individuals with CAI and 11 matched controls performed five repetitions of a single-leg landing task. Biomechanical data were collected from 100ms before to 200ms after touchdown, and were used to calculate touchdown angles, peak angles and moments at the ankle joint in the frontal and sagittal planes. In addition, principal component analyses were used to quantify kinematic and kinetic patterns in the same planes across the 300ms time window. Five trial averages and inter-trial variability were calculated for all variables for each subject. Independent t-tests were used to compare variables between groups. Findings : The CAI group displayed greater inter-trial variability for principal component scores in the sagittal and frontal planes. The sagittal plane principal component captured a phase shift in plantar–flexion motion before touchdown, while the frontal plane principal component captured the general magnitude of motion during the entire movement. The CAI group therefore exhibited greater inter-trial variability in the sagittal plane before touchdown and in the frontal plane during the entire movement. Interpretation : While average motions did not differ between groups, the CAI group displayed greater kinematic inter-trial variability when analyzed with the principal component analysis. More variable joint motions may indicate less dynamic stability in the CAI group, which may originate from greater ligamentous laxity or diminished neuromotor control. [Copyright &y& Elsevier]

Context: Sex differences in neuromuscular control of the lower extremity have been identified as a potential cause for the greater incidence of anterior cruciate ligament (ACL) injuries in female athletes compared with male athletes. Women tend to land in greater knee valgus with higher abduction loads than men, Because knee abduction loads increase ACL strain, the inability to minimize these loads may lead to ACL failure. Objective: To investigate the activation patterns of the quadriceps and hamstrings muscles with respect to the peak knee abduction moment. Design: Cross-sectional study. Setting: Neuromuscular research laboratory. Patients or Other Participants: Twenty-one recreationally active adults (11 women, 10 men). Main Outcome Measure(s): Volunteers performed 3 trials of a 100-cm forward hop. During the hop task, we recorded surface electromyographic data from the medial and lateral hamstrings and quadriceps and recorded lower extremity kinematics and kinetics. Lateral and medial quadriceps-to-hamstrings (Q:H) cocontraction indices, the ratio of medial-to-lateral Q:H cocontraction, normalized root mean square electromyographic data for medial and lateral quadriceps and hamstrings, and peak knee abduction moment were calculated and used in data analyses. Results: Overall cocontraction was lower in women than in men, whereas activation was lower in the medial than in the lateral musculature in both sexes (P < .05). The medial Q:H cocontraction index (R2 - 0.792) accounted for a significant portion of the variance in the peak knee abduction moment in women (P = .001). Women demonstrated less activation in the vastus medialis than in the vastus lateralis (P = .49) and less activation in the medial hamstrings than in the lateral hamstrings (P = .01). Conclusions: Medial-to-lateral Q:H cocontraction appears to be unbalanced in women, which may limit their ability to resist abduction loads. Because higher abduction loads increase strain on the ACL, restoring medial-to-lateral Q:H cocontraction balance in women may help reduce ACL injury risk. [ABSTRACT FROM AUTHOR]

Purpose: This study aimed to comprehensively examine the extent to which knee flexion angle at initial contact, peak knee flexion angle, and vertical ground reaction force (vGRF) contribute to knee extension moments during gait in individuals with anterior cruciate ligament (ACL) reconstruction. Methods: Overground gait biomechanics were evaluated in 26 participants with ACL reconstruction at three time points (about 2, 4, and 6 months after the surgery). Knee flexion angle at initial contact, peak knee flexion angle, peak vGRF, and peak knee extension moment were calculated for each limb during the early stance phase of gait for all three time points. A change score from baseline (time point 2 − time point 1 and time point 3 − time point 1) along with limb symmetry values (ACL − non-ACL limb values) was also calculated for these variables. Multiple linear regressions utilizing classical and Bayesian interference methods were used to determine the contribution of knee flexion angle and vGRF to knee extension moment during gait. Results: Peak knee flexion angle and peak vGRF positively contributed to knee extension moment during gait in both the reconstructed (R 2 = 0.767, P < 0.001) and nonreconstructed limbs (R 2 = 0.815, P < 0.001). Similar results were observed for the symmetry values (R 2 = 0.673, P < 0.001) and change scores (R 2 = 0.731–0.883; all P < 0.001), except that the changes in knee flexion angle at initial contact also contributed to the model using the change scores in the nonreconstructed limb (time point 2 − time point 1: R 2 = 0.844, P < 0.001; time point 3 − time point 1: R 2 = 0.883, P < 0.001). Bayesian regression evaluating the likelihood of these prediction models showed that there was decisive evidence favoring the alternative model over the null model (all Bayes factors >1000). Standardized β coefficients indicated that changes in knee flexion angle had a greater impact (>2×) on knee extension moments than vGRF at both time points in both limbs (β vGRF = 0.204–0.309; β kneeflexion = 0.703–0.831). Conclusions: The findings indicate that both knee flexion angle and peak vGRF positively contribute to altered knee extension moments during gait, but the contribution of knee flexion angle is much greater than vGRF. Therefore, treatment strategies targeting these variables may improve knee loading after ACL reconstruction. [ABSTRACT FROM AUTHOR]

Purpose: High body mass index (BMI) is a strong predictor of posttraumatic osteoarthritis (OA) after anterior cruciate ligament reconstruction (ACLR). Altered gait mechanics are independently affected by BMI and ACLR, and influence OA risk. Yet, evidence directly assessing the impact of high BMI on gait or cartilage characteristics after ACLR are limited. Here, we evaluated if high BMI moderates associations between gait and trochlear cartilage structure in individuals with ACLR. Methods: Treadmill walking biomechanics were evaluated in 40 normal BMI and 24 high BMI participants with ACLR at self-selected speeds. Normalized and absolute peak and cumulative loads (i.e., impulse) were extracted for peak knee flexion and adduction moments (KFM, KAM) and vertical ground reaction force (GRF).Medial and lateral femoral cartilage thickness and medial/lateral thickness ratios were assessed via ultrasound. Results: Those with ACLR and high BMI walked with reduced normalized peak vertical GRFs, and greater absolute peak and cumulative loads compared with normal BMI individuals with ACLR. Those with ACLR and high BMI also exhibited thinner cartilage and greater medial/lateral ratios in ACLR limbs compared with contralateral limbs whereas norma lBMI individuals with ACLR exhibited thicker ACLR limb cartilage. Lastly, greater peak KAM and KAM cumulative load were associated with thicker lateral cartilage and lesser medial/lateral thickness ratios, but only in the high BMI group. Conclusions: We observed those with high BMI after ACLR exhibited trochlear cartilage structural alterations not observed in normal BMI patients, whereas differential associations between loading outcomes and cartilage thickness in ACLR knees were observed between groups. Those with high BMI after ACLR may require different therapeutic strategies to optimize joint health in this subset of patients. [ABSTRACT FROM AUTHOR]

Purpose: Individuals with anterior cruciate ligament reconstruction (ACLR) generally exhibit limb underloading behaviors during walking, but most research focuses on per-step comparisons. Cumulative loading metrics offer unique insight into joint loading as magnitude, duration, and total steps are considered, but few studies have evaluated if cumulative loads are altered post-ACLR. Here, we evaluated if underloading behaviors are apparent in ACLR limbs when using cumulative load metrics and how load metrics change in response to walking speed modifications. Methods: Treadmill walking biomechanics were evaluated in 21 participants with ACLR at three speeds (self-selected (SS); 120% SS and 80% SS). Cumulative loads per step and per kilometer were calculated using knee flexion and adduction moment (KFM and KAM) and vertical ground reaction force (GRF) impulses. Traditional magnitude metrics for KFM, KAM, and GRF were also calculated. Results: The ACLR limb displayed smaller KFM and GRF in early and late stances, but larger KFM and GRF during midstance compared with the contralateral limb (P <0.01). Only GRF cumulative loads (per step and per kilometer) were reduced in the ACLR limb (P <0.01). In response to speed modifications, load magnitudes generally increased with speed. Conversely, cumulative load metrics (per step and per kilometer) decreased at faster speeds and increased at slow speeds (P < 0.01). Conclusions: Patients with ACLR underload their knee in the sagittal plane per step, but cumulatively over the course of many steps/distance, this underloading phenomenon was not apparent. Furthermore, cumulative load increased at slower speeds, opposite to what is identified with traditional single-step metrics. Assessing cumulative load metrics may offer additional insight into how load outcomes may be impacted in injured populations or in response to gait modifications. [ABSTRACT FROM AUTHOR]

Background We have previously reported that an eccentrically-based rehabilitation protocol post-ACLr induced greater quadriceps activation and strength than a neuromuscular electrical stimulation (NMES) intervention and was just as effective as a combined NMES and eccentric intervention. However, the effect an eccentrically-based intervention has on restoring normal knee mechanics during a single-legged landing task remains unknown. Methods Thirty-six individuals post-injury were placed into four treatment groups: NMES and eccentrics, eccentrics-only, NMES-only, standard of care, and healthy controls participated. NMES and eccentrics received a combined NMES and eccentric protocol post-reconstruction (each treatment 2 × per week for 6 weeks), whereas groups NMES-only and eccentric-only received only the NMES or eccentric therapy, respectively. To evaluate knee mechanics limb symmetry, the area under the curve for knee flexion angle and extension moment was derived and then normalized to the contralateral limb. Quadriceps strength was evaluated using the quadriceps index. Findings Compared to healthy, reduced sagittal plane knee limb symmetry was found for groups NMES-only, ECC-only and standard of care for knee extension moment ( P < 0.05). No difference was detected between healthy and NMES and eccentrics ( P > 0.06). No difference between groups was detected for knee flexion angle limb symmetry ( P > 0.05). Greater knee flexion angles and moments over stance were related to quadriceps strength. Interpretation The NMES and eccentrics group was found to restore biomechanical limb symmetry that was most closely related to healthy individuals following ACL reconstruction. Greater knee flexion angles and moments over stance were related to quadriceps strength. [ABSTRACT FROM AUTHOR]

Walking biomechanics are commonly affected after anterior cruciate ligament reconstruction and differ compared to uninjured controls. Manipulating task difficulty has been shown to affect the magnitude of walking impairments in those early after knee surgery but it is unclear if patients in later phases post-op are similarly affected by differing task demands. Here, we evaluated the effects of manipulating walking speed on between-limb differences in ground reaction force and knee biomechanics in those with and without anterior cruciate ligament reconstruction. We recruited 28 individuals with anterior cruciate ligament reconstruction and 20 uninjured control participants to undergo walking assessments at three speeds (self-selected, 120%, and 80% self-selected speed). Main outcomes included sagittal plane knee moments, angles, excursions, and ground reaction forces (vertical and anterior-posterior). We observed walking speed differentially impacted force and knee-outcomes in those with anterior cruciate ligament reconstruction. Between-limb differences increased at fast and decreased at slow speeds in those with anterior cruciate ligament reconstruction while uninjured participants maintained between-limb differences regardless of speed (partial η2 = 0.13–0.33, p < 0.05). Anterior cruciate ligament reconstruction patients underloaded the surgical limb relative to both the contralateral, and uninjured controls in GRFs and sagittal plane knee moments (partial η2 range = 0.13–0.25, p < 0.05). Overall, our findings highlight the persistence of walking impairments in those with anterior cruciate ligament reconstruction despite completing formal rehabilitation. Further research should consider determining if those displaying larger changes in gait asymmetries in response to fast walking also exhibit poorer strength and/or joint health outcomes. • Those with ACLR show larger ground reaction force and knee between-limb differences when walking fast. • Healthy individuals maintain gait symmetry regardless of walk speed. • After ACLR, testing a range of speeds may help detect poor walk patterns after ACLR. [ABSTRACT FROM AUTHOR]