Peak Internal Knee Extension Moment Research Articles

Biomechanical Threshold Values for Identifying Clinically Significant Knee-Related Symptoms Six Months Following Anterior Cruciate Ligament Reconstruction.

Slower habitual walking speed and aberrant gait biomechanics are linked to clinically significant knee-related symptoms and articular cartilage composition changes linked to posttraumatic osteoarthritis (PTOA) following anterior cruciate ligament reconstruction (ACLR). To determine specific gait biomechanical variables that can accurately identify individuals with clinically significant knee-related symptoms post-ACLR, and the corresponding threshold values, sensitivity, specificity, and odds ratios for each biomechanical variable. Cross-sectional analysis. Laboratory. Seventy-one individuals (n=38 female; age=21±4 years; height=1.76±0.11 m; mass=75.38±13.79 kg) who were 6 months post-primary unilateral ACLR (6.2±0.4 months). 3D motion capture of 5 overground walking trials was used to calculate discrete gait biomechanical variables of interest during stance phase (1st and 2nd peak vertical ground reaction force [vGRF]; midstance minimum vGRF; peak internal knee abduction and extension moments; and peak knee flexion angle), along with habitual walking speed. Knee Injury and Osteoarthritis Outcome Scores (KOOS) was used to dichotomize patients as symptomatic (n=51) or asymptomatic (n=20) using the Englund et al. 2003 KOOS guidelines for defining clinically significant knee-related symptoms. Separate receiver operating characteristic (ROC) curves and respective areas under the curve (AUC) were used to evaluate the capability of each biomechanical variable of interest for identifying individuals with clinically significant knee-related symptoms. Habitual walking speed (AUC=0.66), vGRF at midstance (AUC=0.69), and 2nd peak vGRF (AUC=0.76), demonstrated low-to-moderate accuracy for identifying individuals with clinically significant knee-related symptoms. Individuals who exhibited habitual walking speeds ≤1.27 m/s, midstance vGRF ≥0.82 BW, and 2nd peak vGRF ≤1.11 BW, demonstrated 3.13, 6.36, and 9.57 times higher odds of experiencing clinically significant knee-related symptoms, respectively. Critical thresholds for gait variables may be utilized to identify individuals with increased odds of clinically significant knee-related symptoms and potential targets for future interventions.

A Preliminary Investigation into the Neural Correlates of Knee Loading during a Change of Direction Task in Individuals after Anterior Cruciate Ligament Reconstruction.

Central nervous system (CNS) function after ACLR, quantified by the blood oxygen level dependent (BOLD) response, is altered in regions of sensory function during knee movement after ACLR. However, it is unknown how this altered neural response may manifest in knee loading and response to sensory perturbations during sport specific movements. To investigate the relationship among CNS function and lower extremity kinetics, under multiple visual conditions, during 180° change of direction task in individuals with a history of ACLR. Eight participants, 39.3 ± 37.1 months after primary, left ACLR performed repetitive active knee flexion and extension of their involved knee during fMRI scanning. Participants separately performed 3D motion capture analysis of a 180° change of direction task under full vision (FV) and stroboscopic vision (SV) conditions. A neural correlate analysis was performed to associate BOLD signal to knee loading of the left lower extremity. Involved limb peak internal knee extension moment (pKEM) was significantly lower in the SV condition (1.89 ± 0.37 N*m/Kg) compared to the FV condition (2.0 ± 0.34 N*m/Kg) (p = .018). Involved limb pKEM during the SV condition was positively correlated with BOLD signal in the contralateral precuneus and superior parietal lobe (Voxels: 53; p = .017; z-stat max: 6.47; MNI peak: 6, -50, 66). There is a positive association between involved limb pKEM in the SV condition and BOLD response in areas of visual-sensory integration. Activation of contralateral precuneus and superior parietal lobe brain regions may be a strategy to maintain joint loading when vision is perturbed. Level 3.

Association of Jump-Landing Biomechanics With Tibiofemoral Articular Cartilage Composition 12 Months After ACL Reconstruction.

Background:Excessively high joint loading during dynamic movements may negatively influence articular cartilage health and contribute to the development of posttraumatic osteoarthritis after anterior cruciate ligament reconstruction (ACLR). Little is known regarding the link between aberrant jump-landing biomechanics and articular cartilage health after ACLR.Purpose/Hypothesis:The purpose of this study was to determine the associations between jump-landing biomechanics and tibiofemoral articular cartilage composition measured using T1ρ magnetic resonance imaging (MRI) relaxation times 12 months postoperatively. We hypothesized that individuals who demonstrate alterations in jump-landing biomechanics, commonly observed after ACLR, would have longer T1ρ MRI relaxation times (longer T1ρ relaxation times associated with less proteoglycan density).Study Design:Cross-sectional study; Level of evidence, 3.Methods:A total of 27 individuals with unilateral ACLR participated in this cross-sectional study. Jump-landing biomechanics (peak vertical ground-reaction force [vGRF], peak internal knee extension moment [KEM], peak internal knee adduction moment [KAM]) and T1ρ MRI were collected 12 months postoperatively. Mean T1ρ relaxation times for the entire weightbearing medial femoral condyle, lateral femoral condyle (global LFC), medial tibial condyle, and lateral tibial condyle (global LTC) were calculated bilaterally. Global regions of interest were further subsectioned into posterior, central, and anterior regions of interest. All T1ρ relaxation times in the ACLR limb were normalized to the uninjured contralateral limb. Linear regressions were used to determine associations between T1ρ relaxation times and biomechanics after accounting for meniscal/chondral injury.Results:Lower ACLR limb KEM was associated with longer T1ρ relaxation times for the global LTC (ΔR 2 = 0.24; P = .02), posterior LTC (ΔR 2 = 0.21; P = .03), and anterior LTC (ΔR 2 = 0.18; P = .04). Greater ACLR limb peak vGRF was associated with longer T1ρ relaxation times for the global LFC (ΔR 2 = 0.20; P = .02) and central LFC (ΔR 2 = 0.15; P = .05). Peak KAM was not associated with T1ρ outcomes.Conclusion:At 12 months postoperatively, lower peak KEM and greater peak vGRF during jump landing were related to longer T1ρ relaxation times, suggesting worse articular cartilage composition.

Passing return-to-sport criteria and landing biomechanics in young athletes following anterior cruciate ligament reconstruction.

We sought to evaluate the sagittal plane knee joint loading patterns during a double-leg landing task among young athletes who passed or failed return-to-sport (RTS) criteria following anterior cruciate ligament reconstruction reconstruction (ACLR), and in uninjured athletes. Participants completed quadriceps strength testing, a hop test battery, and the International Knee Documentation Committee subjective form following medical RTS clearance. ACLR participants "passed" RTS criteria (RTS-PASS) if they met ≥90 limb symmetry (%) or score on all measures and were categorized as "failing" (RTS-FAIL) if not. All participants completed three-dimensional motion analysis testing. Sagittal plane kinematic and kinetic variables were calculated during a double-leg drop vertical jump task. Mean limb values and limb symmetry indices (LSI; %) were calculated and compared using a one-way analysis of variance (ANOVA) (for LSI) and mixed between-within ANOVA (for group × limb differences). A total of 205 participants were included, with 39 in the RTS-PASS group, 109 in the RTS-FAIL group, and 57 control groups (CTRLs). The RTS-FAIL group demonstrated lower symmetry values for peak vertical ground reaction force, peak internal knee extension moment, and peak knee flexion angle. Group × limb interactions were observed for peak vertical ground reaction force and peak internal knee extension moment. Involved limb values were reduced in the RTS-PASS and RTS-FAIL groups compared to CTRLs, while the RTS-PASS groups had lower uninvolved limb values compared to the RTS-FAIL and CTRLs. Clinical Significance: Young athletes who pass RTS criteria after ACLR land symmetrically during a double-leg task, but symmetry was achieved by reducing loading on both limbs.

Greater explosive quadriceps strength is associated with greater knee flexion at initial contact during landing in females

ABSTRACT This study investigated the influences of explosive quadriceps strength and landing task on sagittal plane knee biomechanics. Forty female participants performed isometric knee extensions on a dynamometer and had lower extremity biomechanics assessed during double-leg jump-landings (DLJL) and single-leg jump-cuts (SLJC). Explosive quadriceps strength was quantified by calculating rate of torque development (RTD) between torque onset and 100 ms after onset on a dynamometer. Participants were stratified into high and low RTD groups. Landing biomechanics were compared using 2 (Group) × 2 (Task) mixed-model ANOVAs. The relationships between quadriceps RTD and landing biomechanics were also assessed using simple, bivariate correlations. Across RTD groups, greater knee flexion at initial contact (KFIC), peak vertical ground reaction force, peak anterior tibial shear force, and peak internal knee extension moment, and lesser peak knee flexion was observed during SLJC compared to DLJL. The high RTD group exhibited significantly greater KFIC than the low RTD group across landing tasks. Greater quadriceps RTD was significantly associated with greater KFIC during SLJC, but not during DLJL. As landing with lesser KFIC is a risk factor for ACL injury, greater explosive quadriceps strength capacity might be beneficial for facilitating the use of safer landing mechanics during athletic tasks.

Obese Youth Demonstrate Altered Landing Knee Mechanics Unrelated to Lower-Extremity Peak Torque When Compared With Healthy Weight Youth

Obese (OB) youth demonstrate altered knee mechanics and worse lower-extremity performance compared with healthy weight (HW) youth. Our objectives were to compare sagittal plane knee landing mechanics between OB and HW youth and to examine the associations of knee and hip extension peak torque with landing mechanics in OB youth. Twenty-four OB and 24 age- and sex-matched HW youth participated. Peak torque was measured and normalized to leg lean mass. Peak knee flexion angle and peak internal knee extension moment were measured during a single-leg hop landing. Paired t tests, Pearson correlation coefficients, and Bonferroni corrections were used. OB youth demonstrated worse performance and lower knee extension (OB: 12.76 [1.38], HW: 14.03 [2.08], P = .03) and hip extension (OB: 8.59 [3.13], HW: 11.10 [2.89], P = .005) peak torque. Furthermore, OB youth demonstrated lower peak knee flexion angles (OB: 48.89 [45.41 to 52.37], HW: 56.07 [52.59 to 59.55], P = .02) and knee extension moments (OB: -1.73 [-1.89 to -1.57], HW: -2.21 [-2.37 to -2.05], P = .0001) during landing compared with HW youth. Peak torque measures were not correlated with peak knee flexion angle nor internal knee extension moment during landing in either group (P > .01). OB youth demonstrated altered landing mechanics compared with HW youth. However, no associations among peak torque measurements and knee landing mechanics were present.

Effects of BMI on Walking Speed and Gait Biomechanics after Anterior Cruciate Ligament Reconstruction.

History of an anterior cruciate ligament reconstruction (ACLR) and high body mass index (BMI) are strong independent risk factors for knee osteoarthritis (KOA) onset. The combination of these risk factors may further negatively affect joint loading and KOA risk. We sought to determine the combined influence of BMI and ACLR on walking speed and gait biomechanics that are hypothesized to influence KOA onset. Walking speed and gait biomechanics (peak vertical ground reaction force [vGRF], peak vGRF instantaneous loading rate [vGRF-LR], peak knee flexion angle, knee flexion excursion [KFE], peak internal knee extension moment [KEM], and peak internal knee abduction moment [KAM]) were collected in 196 individuals with unilateral ACLR and 106 uninjured controls. KFE was measured throughout stance phase, whereas all other gait biomechanics were analyzed during the first 50% of stance phase. A 2 × 2 ANOVA was performed to evaluate the interaction between BMI and ACLR and main effects for both BMI and ACLR on walking speed and gait biomechanics between four cohorts (high BMI ACLR, normal BMI ACLR, high BMI controls, and normal BMI controls). History of an ACLR and high BMI influenced slower walking speed (F1,298 = 7.34, P = 0.007), and history of an ACLR and normal BMI influenced greater peak vGRF-LR (F1,298 = 6.56, P = 0.011). When evaluating main effects, individuals with an ACLR demonstrated lesser KFE (F1,298 = 7.85, P = 0.005) and lesser peak KEM (F1,298 = 6.31, P = 0.013), and individuals with high BMI demonstrated lesser peak KAM (F1,297 = 5.83, P = 0.016). BMI and history of ACLR together influence walking speed and peak vGRF-LR. History of an ACLR influences KFE and peak KEM, whereas BMI influences peak KAM. BMI may need to be considered when designing interventions aimed at restoring gait biomechanics post-ACLR.

Vibration improves gait biomechanics linked to posttraumatic knee osteoarthritis following anterior cruciate ligament injury.

Anterior cruciate ligament reconstruction (ACLR) incurs a high risk of posttraumatic knee osteoarthritis (PTOA). Aberrant gait biomechanics contribute to PTOA and are attributable in part to quadriceps dysfunction. Vibration improves quadriceps function following ACLR, but its effects on gait biomechanics are unknown. The purpose of this study was to evaluate the effects of whole-body vibration (WBV) and local muscle vibration (LMV) on gait biomechanics in individuals with ACLR. Seventy-five volunteers (time since ACLR 27 ± 16 months) were randomized to WBV, LMV, or Control interventions. Walking biomechanics were assessed prior to and following a single exposure to the interventions. Outcomes included pre-post change scores in the ACLR limb for the peak vertical ground reaction force (vGRF) and its loading rate, peak internal knee extension (KEM) and abduction moments, and peak knee flexion and varus angles. LMV produced a significant decrease in the vGRF loading rate (-3.6 BW/s) that was greater than the changes in the WBV (-0.3 BW/s) and Control (0.5 BW/s) groups. Additionally, WBV produced an increase in the peak KEM (0.27% BW × Ht) that was greater than the change in the Control group (-0.17% BW × Ht) but not the LMV group (0.01% BW × Ht). Lower KEM and greater loading rates have been linked to declines in joint health following ACLR. WBV acutely increased the peak KEM and LMV decreased loading rates. These data suggest that vibration has the potential to mitigate aberrant gait biomechanics, and may represent an effective approach for reducing PTOA risk following ACLR.

Changes In Gait Biomechanics Between Level And Downhill Walking Do Not Differ Between Those With Anterior Cruciate Ligament Reconstruction And Controls

Conflicting evidence exists regarding the presence of aberrant gait biomechanics after the first year post-anterior cruciate ligament reconstruction. Overground walking may not elucidate differences in those further removed from surgery due to the unexacting nature of the task. Deleterious gait biomechanics following ACLR are partly attributable to quadriceps dysfunction. Downhill walking may exacerbate aberrant gait biomechanics, as this task places greater demands on the quadriceps compared to level walking. PURPOSE: To compare gait biomechanics between individuals with ACLR and healthy controls during level and downhill walking conditions. METHODS: 24 individuals more than 1 year removed from primary ACLR (83% female, age= 21 ± 3 yr, time since ACLR 44 ± 26 mo, BMI= 23 ± 3 kg/m2) and 24 healthy controls (79% female, age= 21 ± 1 yr, BMI= 24 ± 3 kg/m2) completed both level and downhill (10°grade) gait biomechanics assessments on an instrumented split-belt treadmill at their preferred walking speed. Peak variables were evaluated over the first 50% of stance including the vertical ground reaction force (vGRF), internal knee abduction moment, internal knee extension moment, knee flexion angle, and knee abduction angle. Moments were normalized to %body weight∗height (%BW∗Ht) and vGRF was normalized to %body weight. Dependent variables were compared across groups and conditions via two-way repeated measures ANCOVA controlling for gait speed. RESULTS: There were no significant condition∗group interaction effects nor group main effects for any outcomes. However, there were significant condition main effects for peak internal knee extension moment (p = 0.020, level to downhill mean increase of 0.042 %BW∗Ht) and peak knee flexion angle (p = 0.018, level to downhill mean increase of 13.2°). CONCLUSIONS: Downhill walking necessitates a larger internal extension moment and knee flexion angle compared to level gait. Our results suggest that changes in gait biomechanics between level and downhill conditions do not differ between individuals with ACLR > 1 year post reconstruction and controls. These results suggest that aberrant gait biomechanics may be mitigated over time in those with ACLR.

Gait Biomechanics Linked To Post-traumatic Osteoarthritis Following Anterior Cruciate Ligament Reconstruction Are Improved With Vibration

PURPOSE: Anterior cruciate ligament reconstruction (ACLR) incurs a high risk of post-traumatic knee osteoarthritis (PTOA). Aberrant gait biomechanics contribute to PTOA and are attributable in part to quadriceps dysfunction. Vibration improves quadriceps function following ACLR, but its effects on gait biomechanics are unknown. The purpose of this study was to evaluate the effects of whole body vibration (WBV) and local muscle vibration (LMV) on gait biomechanics in individuals with ACLR. METHODS: 75 volunteers with primary unilateral ACLR (72% females; age 21 ± 3 yr; time since ACLR 27 ± 16 mo) were randomized to WBV, LMV, or Control interventions. WBV and LMV were applied 6 x 1 minute (30Hz, 2g). Walking biomechanics were assessed prior to and following the interventions. Outcomes included the peak vertical ground reaction force (vGRF) and its loading rate, peak internal knee extension and valgus moments, and peak knee flexion and varus angles during the first 50% of stance. vGRF magnitude and rate were normalized to body weight (BW) and moments were normalized as % body weight∗height (%BW∗Ht). ACLR limb change scores (post-pre) for each outcome were compared across groups via one-way ANCOVA controlling for gait speed, time since ACLR, and baseline values. RESULTS: Change scores did not differ across groups for peak knee flexion (p = 0.374) or varus (p = 0.801) angles, vGRF (p = 0.656), or internal valgus moment (p = 0.866). However, changes in vGRF loading rate differed across groups (p = 0.024), with a significant decrease in the LMV group (-3.6 BW/s) that was greater than the changes in the WBV (-0.3 BW/s; p = 0.035) and Control (0.5 BW/s; p = 0.010) groups. Additionally, the change in peak internal extension moment differed across groups (p = 0.016), with a significant increase in the WBV group (0.27 %BW∗Ht) that was greater than the change in the Control group (-0.17 %BW∗Ht; p = 0.005) but not the LMV group (0.01 %BW∗Ht; p = 0.101). CONCLUSIONS: Lower knee extension moments and greater loading rates during gait have been linked to declines in joint health following ACLR. WBV acutely increased the peak knee extension moment and LMV decreased loading rates. These data suggest that vibration has the potential to mitigate aberrant gait biomechanics, and may represent an effective approach for mitigating PTOA risk following ACLR.

Sex-based differences in landing mechanics vary between the drop vertical jump and stop jump

The purpose of the present study was to compare landing mechanics between the stop jump (SJ) and drop vertical jump (DVJ) and to compare sex-based differences in landing mechanics between tasks. 50 healthy recreational athletes were recruited and each participant completed seven SJs and seven DVJs. Peak knee flexion and abduction angle, knee flexion and ab/adduction range of motion (ROM), peak vertical and posterior ground reaction force (GRF), peak internal knee extension and knee adduction moment were computed for the dominant limb during the first landing of both tasks. A two-way ANOVA was used to determine the effects of and interactions between sex (men vs women) and task (SJ vs DVJ) for each outcome. There was an interaction for peak vertical GRF (p = 0.024), knee flexion ROM (p = 0.027), knee ab/adduction ROM (p = 0.047), and peak knee flexion (p = 0.034) and adduction (p = 0.012) moment. The SJ resulted in smaller vertical GRFs, larger posterior GRFs, and larger peak internal knee adduction moments relative to the DVJ (all p < 0.002). Women landed with larger peak knee abduction angles, larger internal knee adduction moments, and smaller knee extension moments relative to men (p = 0.001–0.026). Overall, as the SJ resulted in larger posterior GRFs and internal knee adduction moments, this task produced movements which resemble most anterior cruciate ligament (ACL) injuries and are risk factors for ACL injuries. As the SJ produced more sex-based differences, it may be better suited than the DVJ for ACL injury risk screening. This study therefore stressed the importance of selecting an appropriate landing task for ACL injury prevention research and clinical return to sport assessment.

Somatosensory Function Influences Aberrant Gait Biomechanics Following Anterior Cruciate Ligament Reconstruction.

Osteoarthritis is common following anterior cruciate ligament reconstruction (ALCR), and aberrant gait biomechanics are considered a primary contributor. Somatosensory dysfunction potentially alters gait biomechanics, but this association is unclear. Therefore, the purposes of this investigation were to compare somatosensory function between limbs and evaluate associations between somatosensory function and gait biomechanics linked to osteoarthritis development in individuals with ALCR. Seventy-three volunteers with ALCR participated. Gait biomechanics (peak vertical ground reaction force magnitude and loading rate, peak internal knee extension and valgus moments, peak knee flexion and varus angles, and quadriceps/hamstrings co-activation) were assessed as subjects walked at their preferred speed. The somatosensory function was assessed via joint position sense error (knee flexion) and vibratory perception threshold (femoral epicondyles, malleoli, and first metatarsal). Though somatosensory function did not differ between the ACLR and contralateral limbs, poorer joint position sense in the ACLR limb was associated with lower loading rates and internal knee extension moments, and greater co-activation. Poorer vibratory perception at the medial and lateral malleoli and first metatarsal head in the ACLR limb was associated with lower loading rates, greater internal knee valgus moments and varus angles, and greater co-activation. Poorer vibratory perception at the medial malleolus and first metatarsal head in the contralateral limb was associated with greater peak knee varus angles and internal knee valgus moments. These results suggest that future research evaluating rehabilitation approaches for improving somatosensory function is warranted as a potential approach for restoring normal gait biomechanics and reducing osteoarthritis risk. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 38:620-628, 2020.

Change in Drop-Landing Mechanics Over 2 Years in Young Athletes After Anterior Cruciate Ligament Reconstruction

Background: While between-limb landing asymmetries after anterior cruciate ligament reconstruction (ACLR) are linked with poor function and risk of additional injury, it is not currently understood how landing symmetry changes over time after ACLR. Purpose/Hypothesis: The purpose was to investigate how double-legged drop vertical jump (DVJ) landing and single-legged drop-landing symmetry changed from the time of return-to-sport (RTS) clearance to 2 years later in a prospective cohort of young athletes after ACLR. It was hypothesized that double-legged DVJ landing and single-legged drop-landing symmetry would improve from the time of RTS to 2 years later. Study Design: Descriptive laboratory study. Methods: The authors followed 64 young athletes with primary, unilateral ACLR for 2 years after RTS clearance. At the time of RTS and 2 years later, between-limb symmetry values for biomechanical variables of interest (VOIs) were calculated with 3-dimensional motion analysis during double-legged DVJ and single-legged drop-landing tasks. VOIs included knee flexion excursion, peak internal knee extension moment, peak vertical ground-reaction force, and peak trunk flexion (for single-legged task only). Symmetry values and proportions of participants meeting 90% symmetry cutoffs were compared between time points. Results: For double-legged DVJ landing, symmetry values for all VOIs and the proportions meeting 90% cutoffs for peak internal knee extension moment and peak vertical ground-reaction force were higher at 2 years after RTS as compared with RTS. For single-legged drop-landing, symmetry values were higher for knee flexion excursion and lower for peak trunk flexion at 2 years after RTS as compared with RTS, but the proportions meeting 90% cutoffs for all VOIs did not differ between time points. Conclusion: Double-legged DVJ landing symmetry improved across VOIs over the 2 years after RTS following ACLR, while single-legged drop-landing did not improve as consistently. The implications of longitudinal landing asymmetry after ACLR should be further studied.

No shortage of disagreement between biomechanical and clinical hop symmetry after anterior cruciate ligament reconstruction

BackgroundEvaluating average performance on functional hop tasks can potentially overestimate physical function, as it masks variability present within individual trials and may lead to clinician oversight regarding the overall movement quality. The purpose was to evaluate the trial-by-trial agreement between hop-distance symmetry and knee biomechanics (knee flexion angle, knee extension moment) to reveal the full extent of agreement between these measures. MethodsSixteen individuals with primary, unilateral anterior cruciate ligament reconstruction participated (age: 22(2) y; height: 1.71(0.11) m; mass: 68.94(13.06) kg; gender: 8 males, 8 females; years' post-surgery:4(3) y) in a cross-sectional study. Knee kinematics and kinetics were measured using 3D motion analysis and hop distance was collected during the triple hop for distance. Individual limb difference values for individual hop trials were calculated and values for each trial were dichotomized as pass/fail based on achieving a limb difference of <10%. Cohen's Kappa and confirmatory McNemar's test were performed to determine the level of agreement between measures of physical and biomechanical function between trials. FindingsNo agreement between triple hop and peak knee flexion angle symmetry (κ = 0.033, p = 0.387) and peak internal knee extension moment (κ = 0.022, p = 0.475) were found. McNemar tests confirmed no agreement between hop-distance %LD and knee flexion angle/knee extension moment %LD (p = 0.000). InterpretationThese findings suggest that while individuals after ACLR may on average achieve symmetrical hop-distance, they may not necessarily pass subsequent functional tasks. Further, individual trial-by-trial analyses may provide insight into an individual's true physical capability compared to simply evaluating the average, which may overestimate physical function or mask altered movement strategies.

Co-activation during gait following anterior cruciate ligament reconstruction

BackgroundHeightened co-activation of the quadriceps and hamstrings has been reported following anterior cruciate ligament reconstruction during various tasks, and may contribute to post-traumatic osteoarthritis risk. However, it is unclear if this phenomenon occurs during walking or how co-activation influences gait biomechanics linked to changes in joint health. MethodsCo-activation and gait biomechanics were assessed in 50 individuals with ACLR and 25 healthy controls. Biomechanical outcomes included knee flexion displacement, peak vertical ground reaction force magnitude and rate, peak internal knee extension and valgus moments and rates, sagittal knee stiffness, and the heelstrike transient. Co-activation was calculated for the flexors and extensors collectively (i.e. composite), the medial musculature, and the lateral musculature. FindingsComposite co-activation was greater in the ACLR limb compared to the contralateral limb and the control cohort during the preparatory and heelstrike phases of gait, and co-activation of the medial musculature was greater in the ACLR limb compared to the control cohort during the heelstrike phase. Greater co-activation in multiple gait phases was associated with less knee flexion displacement (r = −0.293 to −0.377), smaller peak vertical ground reaction force magnitude (r = −0.291), smaller peak internal knee extension moment (r = −0.291 to −0.328), and greater peak internal knee valgus moment (r = 0.317). InterpretationIndividuals with ACLR displayed heightened co-activation during walking which was associated with biomechanical outcomes that have been linked to negative changes in joint health following ACLR. These data suggest that excessive co-activation may contribute to the mechanical pathogenesis of post-traumatic osteoarthritis.ClinicalTrials.gov Identifier: NCT02605876.

The effects of mid-flight whole-body and trunk rotation on landing mechanics: implications for anterior cruciate ligament injuries

ABSTRACT The purpose was to quantify the effects of mid-flight whole-body and trunk rotation on knee mechanics in a double-leg landing. Eighteen male and 20 female participants completed a jump-landing-jump task in five conditions: no rotation, testing leg ipsilateral or contralateral (WBRC) to the whole-body rotation direction, and testing leg ipsilateral (TRI) or contralateral to the trunk rotation direction. The WBRC and TRI conditions demonstrated decreased knee flexion and increased knee abduction angles at initial contact (2.6 > Cohen’s dz > 0.3) and increased peak vertical ground reaction forces and knee adduction moments during the 100 ms after landing (1.7 > Cohen’s dz > 0.3). The TRI condition also showed the greatest knee internal rotation angles at initial contact and peak knee abduction and internal rotation angles and peak knee extension moments during the 100 ms after landing (2.0 > Cohen’s dz > 0.5). Whole-body rotation increased contralateral knee loading because of its primary role in decelerating medial-lateral velocities. Trunk rotation resulted in the greatest knee loading for the ipsilateral knee due to weight shifting and mechanical coupling between the trunk and lower extremities. These findings may help understand altered trunk motion in anterior cruciate ligament injuries.

Evaluation of an accelerometer to assess knee mechanics during a drop landing

Non-contact anterior cruciate ligament (ACL) injuries account for 70% of all ACL injuries, and can lead to missed time from activity for athletes and a predisposition for knee osteoarthritis. Prior research has shown that athletes who land in a stiff manner, with larger internal knee adduction and extension moments, are at greater risk for an ACL injury. A three-dimensional accelerometer placed at the tibial tuberosity may prove to be a low-cost means of assessing these risk factors. The primary purpose of this study was to compare tibial accelerations during drop landings with kinematic and kinetic risk factors for ACL injury measured with three-dimensional motion capture. The secondary purpose of this study was to compare these measures between soft and stiff landings. Participants were instructed to land bilaterally in preferred, soft, and stiff manners. Peak knee flexion decreased significantly from soft to stiff landings. Peak internal knee extension moment, peak anterior/posterior knee acceleration, and peak medial knee acceleration all increased significantly from soft to stiff landings. No associations were found between landing condition and either frontal plane knee angle at maximum vertical ground reaction force or peak internal knee adduction moment. Significant positive associations between kinetics and accelerations were found only in the sagittal plane. As such, while a three-dimensional accelerometer could discern between soft and stiff landings in both planes, it may be better suited to predict kinetic risk factors in the sagittal plane.

Gait biomechanics in individuals with patellar tendon and hamstring tendon anterior cruciate ligament reconstruction grafts

Anterior cruciate ligament reconstruction (ACLR) restores joint stability following ACL injury but does not attenuate the heightened risk of developing knee osteoarthritis. Additionally, patellar tendon (PT) grafts incur a greater risk of osteoarthritis compared to hamstring grafts (HT). Aberrant gait biomechanics, including greater loading rates (i.e. impulsive loading), are linked to the development of knee osteoarthritis. However, the role of graft selection on walking gait biomechanics linked to osteoarthritis is poorly understood, thus the purpose of this study was to compare walking gait biomechanics between individuals with HT and PT grafts. Ninety-eight (74 PT; 24 HT) subjects with a history of ACLR performed walking gait at a self-selected speed from which the peak vertical ground reaction force (vGRF) during the first 50% of the stance phase and its instantaneous loading rate, peak internal knee extension and valgus moments, and peak knee flexion and varus angles were obtained. When controlling for time since ACLR and quadriceps strength, there were no differences in any kinetic or kinematic variables between graft types. While not significant, 44% of the PT cohort were identified as impulsive loaders (displaying a heelstrike transient in the majority of walking trials) compared to only 25% of the HT cohort (odds ratio = 2.3). This more frequent observation of impulsive loading may contribute to the greater risk of osteoarthritis with PT grafts. Future research is necessary to determine if impulsive loading and small magnitude differences between graft types contribute to osteoarthritis risk when extrapolated over thousands of steps per day.

Association between kinesiophobia and walking gait characteristics in physically active individuals with anterior cruciate ligament reconstruction

BackgroundIndividuals with anterior cruciate ligament reconstruction (ACLR) demonstrate persistent alterations in walking gait characteristics that contribute to poor long-term outcomes. Higher kinesiophobia, or fear of movement/re-injury, may result in the avoidance of movements that increase loading on the ACLR limb. Research QuestionDetermine the association between kinesiophobia and walking gait characteristics in physically active individuals with ACLR. MethodsWe enrolled thirty participants with a history of unilateral ACLR (49.35 ± 27.29 months following ACLR) into this cross-sectional study. We used the Tampa Scale for Kinesiophobia (TSK-11) to measure kinesiophobia. We collected walking gait characteristics during a 60-s walking trial, which included gait speed, peak vertical ground reaction force (vGRF), instantaneous vGRF loading rate, peak internal knee extension moment (KEM), and knee flexion excursion. We calculated lower extremity kinetic and kinematic measures on the ACLR limb, and limb symmetry indices between ACLR and contralateral limbs (LSI= [ACLR/contralateral]*100). We used linear regression models to determine the association between TSK-11 score and each walking gait characteristic. We determined the change in R2 (ΔR2) when adding TSK-11 scores into the linear regression model after accounting for demographic covariates (sex, Tegner activity score, graft type, time since reconstruction, history of concomitant meniscal procedure). ResultsWe did not find a significant association between kinesiophobia and self-selected gait speed (ΔR2 0.038, P = 0.319). Kinesiophobia demonstrated weak, non-significant associations with kinetic and kinematic outcomes on the ACLR limb and all LSI outcomes (ΔR2 range = 0.001–0.098). SignificanceThese data do not support that kinesiophobia is a critical factor contributing to walking gait characteristics in physically active individuals with ACLR.

Real-time biofeedback can increase and decrease vertical ground reaction force, knee flexion excursion, and knee extension moment during walking in individuals with anterior cruciate ligament reconstruction

Individuals with anterior cruciate ligament reconstruction (ACLR) often exhibit a “stiffened knee strategy” or an excessively extended knee during gait, characterized by lesser knee flexion excursion and peak internal knee extension moment (KEM). The purpose of this study was to determine the effect of real-time biofeedback (RTBF) cuing an acute change in peak vertical ground reaction force (vGRF) during the first 50% of the stance phase of walking gait on: (1) root mean square error (RMSE) between actual vGRF and RTBF target vGRF; (2) perceived difficulty; and (3) knee biomechanics. Acquisition and short-term recall of these outcomes were evaluated. Thirty individuals with unilateral ACLR completed 4 separate walking sessions on a force-measuring treadmill that consisted of a control (no RTBF) and 3 experimental loading conditions using RTBF including: (1) 5% vGRF increase (high-loading), (2) 5% vGRF decrease (low-loading) and (3) symmetric vGRF between limbs. Bilateral biomechanical outcomes were analyzed during the first 50% of the stance phase, and included KEM, knee flexion excursion, peak vGRF, and instantaneous vGRF loading rate (vGRF-LR) for each loading condition. Peak vGRF significantly increased and decreased during high-loading and low-loading, respectively compared to control loading. Instantaneous vGRF-LR, peak KEM and knee flexion excursion significantly increased during the high-loading condition compared to low-loading. Perceived difficultly and RMSE were lower during the symmetrical loading condition compared to the low-loading condition. Cuing an increase in peak vGRF may be beneficial for increasing KEM, knee flexion excursion, peak vGRF, and vGRF-LR in individuals with ACLR. Clinical Trials Number: NCT03035994.