Greater Knee Flexion Angles Research Articles

Strategies for knee stabilising and pivot-shift avoidance in a step-down and cross-over task observed sub-acutely after anterior cruciate ligament reconstruction

BackgroundIndividuals with a recent anterior cruciate ligament reconstruction may demonstrate an altered movement strategy for protecting the knee and maintaining stability. Altered knee movement might lead to abnormal intra-articular load, potentially contributing to early knee osteoarthritis onset. A protective strategy may be particularly evident during active tasks that induce a pivot-shift manoeuvre, such as a step-down and cross-over task. In this study, we investigated whether knee joint mechanics and muscle activity differed between participants early (∼3 months) following reconstruction (n = 35) to uninjured controls (n = 35) during a step-down and cross-over task with a 45° change-of-direction. MethodsWe used motion capture, force plates and surface electromyography to compare time-normalised curves of sagittal and transverse-plane knee mechanics and muscle activity during the cross-over phase between groups using functional t-tests. We also compared knee mechanics between sides within the injured group and compared discrete outcomes describing the cross-over phase between groups. FindingsCompared to controls, the injured participants had greater knee flexion angle and moment, lower internal rotation moment, more preparatory foot rotation of the pivoting leg, a smaller cross-over angle, and a longer cross-over phase for both the injured and uninjured sides. The injured leg also had greater biceps femoris and vastus medialis muscle activity compared to controls and different knee mechanics than the uninjured leg. InterpretationIndividuals with anterior cruciate ligament reconstruction showed a knee-stabilising and pivot-shift avoidance strategy for both legs early in rehabilitation. These results may reflect an altered motor representation and motivate considerations early in rehabilitation.

Eighteen-Month Changes in Physical Activity, Body Weight, Quadriceps Strength, and Gait Biomechanics during the COVID-19 Pandemic.

This study assessed the effects of the COVID-19 pandemic restrictions/lockdowns on physical activity levels, body mass, quadriceps strength, and gait biomechanics over 18 months. Ten healthy men were assessed at baseline (~14 wk before first lockdown) and 17.9 ± 0.3 months later (<1 wk after second lockdown). At both times, physical activity levels, body mass, and quadriceps strength were acquired using the International Physical Activity Questionnaire, a force plate, and a dynamometer, respectively. Gait data were also acquired using a motion capture system and force plates during self-paced walking, from which spatiotemporal parameters, knee angles, and external moments were computed. Baseline and follow-up measurements were compared using two-tailed paired t -tests ( α = 0.05). At follow-up, participants spent less time doing vigorous physical activity (∆ = -76 ± 157 min·wk -1 , P = 0.048), exhibited a tendency toward increased sedentary time (∆ = +120 ± 162 min·d -1 , P = 0.056), weighed more (∆ = +2.5 ± 2.8 kg, P = 0.021), and showed a trend toward reduced quadriceps strength (∆ = -0.29 ± 0.45 (N·m)·kg -1 , P = 0.071) compared with baseline. At follow-up, participants walked slower (∆ = -0.09 ± 0.07 m·s -1 , P = 0.005), had greater knee flexion angles at heel strike (∆ = +2.2° ± 1.8°, P = 0.004) and during late stance (∆ = +2.2° ± 1.8°, P = 0.004), had reduced knee extension moments (∆ = -0.09 ± 0.09 (N·m)·kg -1 , P = 0.012) and knee internal rotation moments (∆ = -0.02 ± 0.02 (N·m)·kg -1 , P = 0.012) during late stance. Healthy men exhibited reduced physical activity levels, increased body weight, a tendency toward reduced quadriceps strength, and altered gait biomechanics over the initial 18 months of the COVID-19 pandemic-alterations that could have far-reaching health consequences.

Beyond peak torque: Longitudinal analysis of angle-specific isokinetic knee torques in collegiate athletes post-ACLR

ObjectivesTo investigate changes in angle-specific knee extensor torque between limbs from 4 to 12 months post-anterior cruciate ligament reconstruction(ACLR) in Division I collegiate athletes at two different isokinetic velocities. DesignCase-series study. SettingLaboratory-based. ParticipantsIsokinetic knee flexion and extension assessments of 17 athletes (11 female) at 4, 8, and 12 months after ACLR with bone-patellar tendon-bone autograft were evaluated. Main outcome measuresAngle-specific curve analyses were performed using statistical parametric mapping for torque data obtained between 14 and 101° at 60°/s and 240°/s velocities. ResultsAt 60°/s, knee extensor torque of the operated limb increased between 4 and 8 months (18–101°,p < 0.001), 4 and 12 months (28–101°,p < 0.001), and 8 and 12 months post-surgery (62–70°,p = 0.002, and 79–90°,p < 0.001). Knee extensor torque was lower in the operated limb compared to the non-operated limb at 4 (47–97°,p < 0.001) and 8 months (65–90°,p < 0.001) for 60°/s, at 4 (21–89°,p < 0.001) and 8 months (50–77°,p < 0.001) for 240°/s, with no between-limb differences at 12 months post-ACLR for both velocities. ConclusionsOperated limb knee extensor torque increased throughout the majority of knee range of motion from 4 to 12 months post-ACLR at both isokinetic velocities, while non-operated limb torque only improved through a reduced arc of motion in greater knee flexion angles.

Depth of single-leg squat influences the two-dimensional analysis of knee, hip, and pelvis frontal plane motion in pain-free women

BackgroundThe single-leg squat (SLS) is often used to measure two-dimensional frontal plane motion; however, there is a variability in the SLS depth across studies. Research questionAre knee abduction (KABD), hip adduction (HADD), pelvic drop (PD), and lateral trunk flexion (LTF) angles different at greater knee flexion angles during a SLS? MethodsTwenty pain-free females (age=22.3 ± 1.1 years, height=1.68 ± 0.06 m, mass=63.1 ± 11.7 kg) participated in this cross-sectional study. Participants performed five SLSs to the lowest depth comfortable, keeping pace with a metronome, while being video recorded in the frontal and sagittal planes. The middle three SLSs were used for analysis. KABD, HADD, PD, and LTF angles were measured at 30º, 45º, 60º, 75º, and 90º of knee flexion using extracted images. Linear mixed model analyses were used to compare across knee flexion angles and clinical significance was determined by comparing angle changes to the standard error of measurement (SEM). ResultsWe observed significant differences for KABD (F=14.69, p < .001), HADD (F=46.29, p < .001), and PD (F=27.27, p < .001) among knee flexion angles. Post-hoc analyses revealed that KABD significantly increased at every increase of knee flexion angle (p ≤ .05, d=0.54–1.95), as did HADD (p ≤ .05, d=0.64–3.85) and PD (p ≤ .05, d=0.61–3.03). Changes in KABD, HADD, and PD often exceeded SEM for all changes in knee flexion angles. SignificanceKnee, hip, and pelvic frontal plane motions are influenced by knee flexion angles during 2D analysis of a SLS task. Our results highlight the importance of standardizing SLS depth during research and clinical practice to ensure appropriate comparisons across measurements.

Differences in Gait Biomechanics Between Adolescents and Young Adults With Anterior Cruciate Ligament Reconstruction.

Adolescents and adults are treated similarly in rehabilitation and research despite differences in clinical recovery after anterior cruciate ligament reconstruction (ACLR). Aberrant gait is a clinical outcome associated with poor long-term health post-ACLR but has not been compared between adolescents and adults. To compare gait biomechanical waveforms throughout stance between adolescents (<18 years old) and young adults (≥18 years old) post-ACLR. Case-control study. Laboratory. Adolescents (n = 13, girls = 77%, age = 16.7 ± 0.6 years, height = 1.7 ± 0.1 m, weight = 22.2 ± 3.7 kg/m2) were identified from a cross-sectional cohort assessing clinical outcomes 6 to 12 months post-ACLR. Young adults (n = 13, women = 77%, age = 22.3 ± 4.0 years, height = 1.7 ± 0.1 m, weight = 22.9 ± 3.3 kg/m2) were matched based on sex, time since surgery (±2 months), and body mass index (±3 kg/m2). Participants performed 5 gait trials at their habitual speed. Three-dimensional gait biomechanics and forces were collected. Vertical ground reaction force normalized to body weight (xBW), knee-flexion angle (°), knee-abduction moment (xBW × height), and knee-extension moment (BW × height) waveforms were calculated during the stance phase of gait (0%-100%). Habitual walking speed was compared using independent t tests. We used functional waveforms to compare gait biomechanics throughout stance with and without controlling for habitual walking speed by calculating mean differences between groups with 95% CIs. Adolescents walked with slower habitual speeds compared with adults (adolescents = 1.1 ± 0.1 m/s, adults = 1.3 ± 0.1 m/s, P < .001). When gait speed was not controlled, adolescents walked with less vertical ground reaction force (9%-15% of stance) and knee-abduction moment (12%-25% of stance) during early stance and less knee-extension moment during late stance (80%-99% of stance). Regardless of their habitual walking speed, adolescents walked with greater knee-flexion angle throughout most stances (0%-21% and 29%-100% of stance). Adolescents and adults demonstrated different gait patterns post-ACLR, suggesting that age may play a role in altered gait biomechanics.

Anterolateral Structure Reconstructions With Different Tibial Attachment Sites Similarly Improve Tibiofemoral Kinematics and Result in Different Graft Force in Treating Knee Anterolateral Instability

To compare the biomechanical effects of anterolateral structure reconstructions (ALSRs) with different tibial attachments on tibiofemoral kinematics and anterolateral structure (ALS) graft forces. Eight cadaveric knees were tested in a customized knee testing system, using a novel pulley system to simulate more muscle tensions by loading the iliotibial band at 30 N and quadriceps at 10 N in all testing states. Anterior stability during anterior load and anterolateral rotatory stability during 2 simulated pivot-shift tests (PST1 and PST2) were evaluated in 5 states: intact, ALS-deficient (Def), ALSR-Ta (anterior tibial site), ALSR-Tm (middle tibial site), and ALSR-Tp (posterior tibial site). Tibiofemoral kinematics and resulting ALS graft forces against the applied loads were measured and compared in the corresponding states. In anterior load, 3 ALSRs mitigated the anterior laxities of the ALS Def state at all degrees, which were close to intact state at 0° and 30° but showed significantly overconstraints at 60° and 90°. In both PSTs, all ALSRs significantly reduced the anterolateral rotatory instability of ALS Def, whereas the significant overconstraints were detected in ALSR-Ta and ALSR-Tm at greater knee flexion angles. All ALS grafts carried forces in resisting anterior and pivot-shift loads. Only ALS graft force in ALSR-Ta increased continuously with knee flexion angles. The ALS graft forces carried by ALSR-Ta were significantly larger than those by ALSR-Tp and ALSR-Tm when resisting anterior load and PSTs at greater knee flexion angles. ALSRs with different tibial attachment sites similarly restored knee laxities close to the native tibiofemoral kinematics in an ALS-deficient knee, whereas the ALSR-Tp showed less propensity for overconstraining the knee at greater flexion angles. The ALS graft in ALSR-Ta carried more forces than those in ALSR-Tp and ALSR-Tm against simulated loads. Altering the tibial attachment sites of ALSRs may not significantly affect tibiofemoral kinematics at most degrees whereas the posterior may have less overconstraints at greater flexion angles. However, ALS graft positioning at a more anterior tibial attachment site may carry more forces in resisting anterior and pivot-shift loads.

Sex-Based Differences in the Drop Vertical Jump as Revealed by Video Motion Capture Analysis Using Artificial Intelligence.

Background:Sex-based biomechanical differences during a drop vertical jump (DVJ) may explain the increased risk of anterior cruciate ligament injury in females. Video motion capture using artificial intelligence (VMocap) is a new method for accurate motion analysis.Purpose:To use VMocap to identify sex-based differences in biomechanics during a DVJ in Asian athletes.Study Design:Controlled laboratory study.Methods:A total of 63 female and 61 male Asian soccer players volunteered for this study in 2018. Participants performed a bilateral DVJ using VMocap, and the knee valgus angle (KVA), knee flexion angle (KFA), hip flexion angle (HFA), and lower leg anterior inclination angle (LAIA) were calculated from the motion capture data. These joint angles and inclination angles were evaluated at the time of highest point of the first jump (H1), initial contact (IC), maximum knee flexion (MKF), toe-off (TO), and highest point of the second jump (H2). The unpaired t test was used to compare sex-based differences.Results:At H1, the KVA in females showed more valgus (−2.9° vs −5.4°) and the LAIA in females was greater (29.1° vs 25.7°) versus males (P < .01 for both). At IC, the KVA in females showed more valgus (−1.3° vs −3.0°) and females had a greater KFA (20.8° vs 14.3°) and LAIA (5.1° vs 0.0°) compared with males (P < .01 for all). At MKF, female KVA showed more valgus (6.2° vs −9.5°), and females had greater LAIA (36.6° vs 34.6°), smaller KFA (77.5° vs 87.5°), and smaller HFA (55.8° vs 82.0°) compared with males (P < .01 for all). At TO, female KVA showed more valgus (−0.7° vs −3.1°) and female KFA, HFA, and LAIA were greater (31.7° vs 19.2°; 19.9° vs 16.4°; and 18.2° vs 11.5°, respectively) than males (P < .01 for all). At H2, females had a greater KFA (18.6° vs 14.6°) and LAIA (13.3° vs 9.9°) than males (P < .04 for both).Conclusion:Asian female soccer players showed increased KVA and LAIA, decreased KFA and HFA at MKF, and increased KFA at IC and TO compared with their male counterparts in this analysis of the DVJ.Clinical Relevance:Elucidation of kinematic differences between the sexes can aid in predicting injuries.

Application of Principal Component Analysis to Forward Reactive Stepping: Whole-body Movement Strategy Differs as a Function of Age and Sex.

Differences in reactive stepping strategy to recover balance have been investigated as a function of age and sex, but to date have been measured using discrete step or joint specific measures. It is unknown how whole-body strategy or underlying motor control objectives differ between age and sex groups in forward reactive stepping. Does whole-body movement and/or motor control strategy differ as a function of age or sex in a forward reactive step to maintain balance? Forty young and older adults (45 females, 35 males) participated in this study. All participants performed five reactive stepping trials in response to a forward balance perturbation while whole-body kinematics and ground reaction forces were collected. Features of whole-body movement strategy were determined using a principal component analysis model. Average principal component (PC) scores were compared between groups as a measure of whole-body movement strategy and within participant relative standard deviation of PC scores were compared to determine if motor control objectives differed across groups. Significant differences in reactive stepping strategy were observed both as a function of age and sex. Older adults had a greater step length and width, greater anterior trunk and pelvis translation, greater knee flexion angles and anterior translation of the hip joint on the stepping leg compared to young participants. Males had lesser step length and width, as well as greater trunk flexion compared to females. No differences in relative standard deviation of PC scores were observed between age or sex-based groups suggesting that motor control objectives were similar between groups. This study demonstrates how whole-body movement strategy differs as a function of age and sex, which explains why previously reported discrete outcomes occur. Additionally, it does not seem that motor control strategy objectives differ between age or sex groups in forward reactive stepping.

Preoperative and Postoperative Walking Gait in Women With Acetabular Labral Tears and Femoroacetabular Impingement Syndrome.

Symptomatic femoroacetabular impingement syndrome (FAIS) is a painful condition that leads to decreased function. How walking gait changes over time within the first year after surgery for FAIS and how these changes present in women are currently unknown. To determine biomechanical gait differences between women with FAIS or labral tears and control individuals preoperatively and at 3 and 6 months postoperatively. Case-control study. Laboratory. A total of 18 female participants comprising 9 women in the FAIS group (age = 31.44 ± 7.47 years, height = 1.73 ± 0.08 m, mass = 73.61 ± 14.44 kg) and 9 women in the control group (age = 31.44 ± 6.65 years, height = 1.69 ± 0.06 m, mass = 60.93 ± 5.58 kg). Between-groups comparisons of the Hip Outcome Score Activities of Daily Living subscale (HOSADL) and gait biomechanics were conducted preoperatively and at the 3- and 6-month postoperative sessions. Statistical parametric mapping was performed on normalized time-series data. Preoperatively, the FAIS group had poor HOSADL scores (FAIS group = 64.1 ± 15.4 versus control group = 100.0 ± 0, P < .001), walked 15% slower, and exhibited several gait differences compared with the control group. Three months postoperatively, the FAIS group displayed greater vertical ground reaction force (P = .01), ankle-dorsiflexion angle (P = .02), and external dorsiflexion moment (P = .01) in midstance, as well as a greater knee-flexion angle through the second half of stance (P < .001). The FAIS group also demonstrated less hip-extension angle (P = .02) and hip-abduction angle (P = .01) through the second half of stance, which transitioned into less hip extension (P = .040) and hip abduction (P = .03) during the subsequent swing phase. The FAIS group improved their HOSADL to 87.6 ± 7.6 by 6 months postoperatively and had a greater dorsiflexion moment (P = .003) and ankle external rotation during stance (P = .03). In addition, the FAIS group showed a greater external hip external-rotation moment in late stance (P < .001). The biomechanical differences between groups were most evident at 3 months postoperatively, suggesting that women with FAIS had more postoperative gait compensations in the short term after surgery. By 6 months postoperatively, patient-reported outcomes had markedly improved, and the FAIS group displayed few gait differences compared with the control group.

Synovial fluid concentrations of matrix Metalloproteinase-3 and Interluekin-6 following anterior cruciate ligament injury associate with gait biomechanics 6 months following reconstruction

To compare gait biomechanics 6 months following anterior cruciate ligament (ACL) reconstruction (ACLR) between patients with the highest and lowest concentrations of synovial fluid (SF) interleukin-6 (IL-6) and matrix metalloproteinase-3 (MMP-3), as well as compared to uninjured controls. SF concentrations of IL-6 and MMP-3 were collected 7±4 days post injury in 38 ACL injured patients (55% female, 21±4yrs, 25.3±5.2BMI). ACL injured individuals were stratified into the lowest and highest quartiles based on IL-6 (IL-6Lowest and IL-6Highest) and MMP-3 (MMP-3Lowest and MMP-3Highest) concentrations. Gait biomechanics were collected on the injured limb 6 months post-ACLR and in 38 uninjured controls (50% female, 21±3yrs, 23.8±2.8BMI). Functional analyses of variance were used to compare vertical ground reaction force (vGRF), knee flexion angle (KFA), and internal knee extension moment (KEM) waveforms throughout stance phase of gait to determine the proportions of stance differing between limbs and groups. Compared to uninjured controls, IL-6High and MMP-3High ACL subgroups demonstrated lesser vGRF (largest differences: IL-6, 7.88%BW; MMP-3, 11.05%BW) during early-stance and greater vGRF (largest differences: IL-6, 6.21%BW; MMP-3, 5.85%BW) in mid-stance, lesser KFA (largest differences: IL-6, 3.11°; MMP-3, 3.72°) and lesser KEM (largest differences: IL-6, 0.96%BW•m; MMP-3, 1.07%BW•m) in early-stance, as well as greater KFA in mid-stance (largest differences: IL-6, 1.5°; MMP-3, 2.95°). High SF concentrations of a proinflammatory cytokine and a degradative enzyme early post-ACL injury are associated with aberrant gait biomechanics in the injured limb at 6 months post-ACLR (i.e., lesser vGRF, KFA and KEM) linked to posttraumatic osteoarthritis development.

Stronger Subjects Select a Movement Pattern That May Reduce Anterior Cruciate Ligament Loading During Cutting.

Davies, WT, Ryu, JH, Graham-Smith, P, Goodwin, JE, and Cleather, DJ. Stronger subjects select a movement pattern that may reduce anterior cruciate ligament loading during cutting. J Strength Cond Res 36(7): 1853-1859, 2022-Increased strength has been suggested to reduce the incidence of anterior cruciate ligament (ACL) injury as part of wider neuromuscular training programs; however, the mechanism of this is not clear. Cutting is a high-risk maneuver for ACL injury, but limited research exists as to how strength affects sagittal plane biomechanics during this movement. Sixteen subjects were split into a stronger and weaker group based on their relative peak isometric strength in a unilateral squat (stronger: 29.0 ± 3.4 N·kg-1 and weaker: 18.3 ± 4.1 N·kg-1). Subjects performed 45° cuts with maximal intent 3 times, at 3 different approach velocities (2, 4, and 6 m·s-1). Kinematics and ground reaction forces were collected using optical motion capture and a force platform. The stronger group had lower knee extensor moments, larger hip extensor moments, and a greater peak knee flexion angle than the weaker group (p < 0.05). There was a trend for greater knee flexion at initial contact in the stronger group. There were no differences in resultant ground reaction forces between groups. The stronger group relied more on the hip than the knee during cutting and reached greater knee flexion angles. This could decrease ACL loading by reducing the extensor moment required at the knee during weight acceptance. Similarly, the greater knee flexion angle during weight acceptance is likely to be protective of the ACL.

Patient-Reported Outcomes and Knee Mechanics Correlate With Patellofemoral Deep Cartilage UTE-T2* 2 Years After Anterior Cruciate Ligament Reconstruction

Background: Patellofemoral joint degeneration and dysfunction after anterior cruciate ligament reconstruction (ACLR) are increasingly recognized as contributors to poor clinical outcomes. Purpose: To determine if greater deep cartilage matrix disruption at 2 years after ACLR, as assessed by elevated patellofemoral magnetic resonance imaging (MRI) ultrashort echo time–enhanced T2* (UTE-T2*), is correlated with (1) worse patient-reported knee function and pain and (2) gait metrics related to patellofemoral tracking and loading, such as greater external rotation of the tibia at heel strike, reduced knee flexion moment (as a surrogate of quadriceps function), and greater knee flexion angle at heel strike. Study Design: Cross-sectional study; Level of evidence, 3. Methods: MRI UTE-T2* relaxation times in patellar and trochlear deep cartilage were compared with patient-reported outcomes and ambulatory gait metrics in 60 patients with ACLR at 2 years after reconstruction. ACLR gait metrics were compared with those of 60 uninjured reference patients matched by age, body mass index, and sex. ACLR UTE-T2* values were compared with those of 20 uninjured reference patients. Results: Higher trochlear UTE-T2* values were associated with worse Knee injury and Osteoarthritis Outcome Scores (KOOS) Sport/Recreation subscale scores (rho = −0.32; P = .015), and showed a trend for association with worse KOOS Pain subscale scores (rho = −0.26; P = .045). At 2 years after ACLR, greater external rotation of the tibia at heel strike was associated with higher patellar UTE-T2* values (R = 0.40; P = .002); greater knee flexion angle at heel strike was associated with higher trochlear UTE-T2* values (rho = 0.39; P = .002); and greater knee flexion moment showed a trend for association with higher trochlear UTE-T2* values (rho = 0.30; P = .019). Patellar cartilage UTE-T2* values, knee flexion angle at heel strike, and external rotation of the tibia at heel strike were all elevated in ACLR knees as compared with reference knees (P = .029, .001, and .044, respectively). Conclusion: Patellofemoral deep cartilage matrix disruption, as assessed by MRI UTE-T2*, was associated with reduced sports and recreational function and with gait metrics reflective of altered patellofemoral loading. As such, the findings provide new mechanistic information important to improving clinical outcomes related to patellofemoral dysfunction after ACLR.

Knee flexion angle and muscle activations control the stability of an anterior cruciate ligament deficient joint in gait

Anterior cruciate ligament (ACL) is a primary structure and a commonly injured ligament of the knee joint. Some patients with ACL deficiency (ACLD) experience joint instability and require a reconstructive surgery to return to daily routines, some can adapt by limiting their activities while others, called copers, can return to high-level activities with no instability. We investigated the effects of alterations in the knee flexion angle (KFA) and muscle force activations on the stability and biomechanics of ACLD joints at 25, 50, and 75% periods of gait stance. ACLD joint stability is controlled by variations in both KFA and knee muscle forces. For the latter, a parameter called activity index is defined as the ratio of forces in ACL antagonists (quadriceps and gastrocnemii) to those in ACL agonists (hamstrings). Under a greater KFA (2–6° beyond the mean of reported values in healthy subjects), an ACLD joint regains its pre-injury stability levels. The ACLD joint stability also markedly improves at smaller quadriceps and larger hamstrings forces (activity indices of 2.0–3.6 at 25%) at the first half of stance and smaller gastrocnemii and larger hamstrings forces (activity indices of 0.1–1.1 at 50% and 0.1–1.2 at 75%) at the second half of stance. Activity index and KFA are both crucial when assessing the dynamic stability of an ACLD joint. These results are helpful in our understanding of the biomechanics and stability of ACLD joints towards improved prevention and treatment strategies.

Biomechanical effects of manipulating peak vertical ground reaction force throughout gait in individuals 6–12 months after anterior cruciate ligament reconstruction

BackgroundWe aimed to determine the effect of cueing an increase or decrease in the vertical ground reaction force impact peak (peak in the first 50% of stance) on vertical ground reaction force, knee flexion angle, internal knee extension moment, and internal knee abduction moment waveforms throughout stance in individuals 6–12 months after an anterior cruciate ligament reconstruction. MethodsTwelve individuals completed 3 conditions (High, Low, and Control) where High and Low Conditions cue a 5% body weight increase or decrease, respectively, in the vertical ground reaction force impact peak compared to usual walking. Biomechanics during High and Low Conditions were compared to the Control Condition throughout stance. FindingsThe High Condition resulted in: (a) increased vertical ground reaction forces at each peak and decreased during mid-stance, (b) greater knee excursion (i.e., greater knee flexion angle in early stance and a more extended knee in late stance), (c) greater internal extension moment for the majority of stance, and (d) lesser second internal knee abduction moment peak. The Low Condition resulted in: (a) vertical ground reaction forces decreased during early stance and increased during mid-stance, (b) decreased knee excursion, (c) increased internal extension moment throughout stance, and (d) decreased internal knee abduction moment peaks. InterpretationCueing a 5% body weight increase in vertical ground reaction force impact peak resulted in a more dynamic vertical ground reaction force loading pattern, increased knee excursion, and a greater internal extension moment during stance which may be useful in restoring gait patterns following anterior cruciate ligament reconstruction.

Effect of High-Heeled Shoes on Balance and Lower-Extremity Biomechanics During Walking in Experienced and Novice High-Heeled Shoe Wearers.

Wearing high-heeled shoes and carrying asymmetrical loads are common in ladies. However, knowledge of the effects of wearing high-heeled shoes on balance and lower-extremity biomechanics in experienced and novice high-heeled shoe wearers is lacking. The study aims to examine the effects of high-heeled shoes and asymmetrical load carrying on joint kinematics and kinetics of the lower extremity during walking as well as balance in experienced and novice high-heeled shoe wearers. Fifteen experienced and 15 novice high-heeled shoes wearers participated in this study. Using a motion analysis system, kinematic and kinetic data were collected while participants walked at their preferred speed in six conditions created from two types of shoes (9-cm high-heeled shoes and flat-heeled shoes) and three weights of symmetrical load (0%, 5%, and 10% of body weight). Stride time and length, step length, double support time, peak joint angles, and joint moments in a sagittal plane were analyzed. Single-leg and tandem-leg stance tests were performed in each condition. Compared with experienced high-heeled shoe wearers, novice high-heeled shoe wearers had longer double support time and shorter stride length during 10% of body weight asymmetrical load walking; walked with greater knee flexion angle, smaller knee range of motion, and smaller ankle dorsiflexor moment; and scored lower in the single-leg and tandem-leg stance tests. Novice high-heeled shoe wearers need to alter their lower-limb joint angles and moments to adjust to high-heeled shoes to achieve balance during gait while carrying an asymmetrical load.

Surface properties affect the interplay between fascicles and tendinous tissues during landing.

Muscle-tendon units are forcefully stretched during rapid deceleration events such as landing. Consequently, tendons act as shock absorbers by buffering the negative work produced by muscle fascicles likely to prevent muscle damage. Landing surface properties can also modulate the amount of energy dissipated by the body, potentially effecting injury risk. This study aimed to evaluate the influence of three different surfaces on the muscle-tendon interactions of gastrocnemius medialis (GM), and vastus lateralis (VL) during single- and double-leg landings from 50cm. Ultrasound images, muscle activity and joint kinematics were collected for 12 participants. Surface testing was also performed, revealing large differences in mechanical behavior. During single-leg landing, stiffer surfaces increased VL fascicle lengthening and velocity, and muscle activity independent of joint kinematics while GM length changes showed no difference between surfaces. Double-leg landing resulted in similar fascicle and tendon behavior despite greater knee flexion angles on stiffer surfaces. This demonstrates that VL fascicle lengthening is greater when the surface stiffness increases, when performing single-leg landing. This is due to the combination of limited knee joint flexion and lower surface absorption ability which resulted in greater mechanical demand mainly withstood by fascicles. GM muscle-tendon interactions remain similar between landing surfaces and types. Together, this suggests that surface damping properties primarily affect the VL muscle-tendon unit with a potentially higher risk of injury as a result of increased surface stiffness when performing single-leg landing tasks.

Knee Biomechanical Deficits During a Single-Leg Landing Task Are Addressed With Neuromuscular Training in Anterior Cruciate Ligament-Reconstructed Athletes.

Faulty neuromuscular and biomechanical deficits of the knee are nearly ubiquitous in athletes after anterior cruciate ligament (ACL) reconstruction (ACLR). Knee biomechanical deficits are directly associated with an increased risk of second ACL injury, which typically occurs during a sports-related movement on a single limb. To date, the biomechanical effects of a neuromuscular training (NMT) program on knee biomechanics during a single-leg landing task have not been investigated. Prospective Cohort Study. Controlled laboratory setting. Eighteen ACLR and 10 control athletes. Neuromuscular training. Knee kinematics and kinetics. There were no significant interactions of session and limb (P > 0.05) for the athletes with ACLR after training. However, there were several significant main effects of session (P < 0.05) for knee kinematics and kinetics during the single-leg landing task. After training, the athletes with ACLR landed with greater knee flexion angles, decreased knee abduction angles, increased knee flexion range of motion, and decreased knee excursion. Also, the ACLR athletes landed with lower knee flexion moments, greater knee adduction moments, and lower peak vertical ground reaction force. Post-training comparison of the ACLR and control cohorts found no significant interactions of group and limb (P > 0.05) and only a significant main effect of group (P < 0.05) for frontal plane knee angle at initial contact. The athletes with ACLR landed with greater knee adduction angles than the control group. Deficits in knee biomechanics that are associated with an increased risk of ACL injury are attenuated after completion of this NMT program.

The Effect of Foot Landing Type on Lower-extremity Kinematics, Kinetics, and Energy Absorption during Single-leg Landing

Objective: The aim of this study was to examine the effect of foot landing type (forefoot vs. rearfoot landing) on kinematics, kinetics, and energy absorption of hip, knee, and ankle joints. Method: Twenty-five healthy men performed single-leg landings with two different foot landing types: forefoot and rearfoot landing. A motion-capture system equipped with eight infrared cameras and a synchronized force plate embedded in the floor was used. Three-dimensional kinematic and kinetic parameters were compared using paired two-tailed Student's t-tests at a significance level of .05. Results: On initial contact, a greater knee flexion angle was shown during rearfoot landing (p < .001), but the lower knee flexion angle was found at peak vertical ground reaction force (GRF) (p < .001). On initial contact, ankles showed plantarflexion, inversion, and external rotation during forefoot landing, while dorsiflexion, eversion, and internal rotation were shown during rearfoot landing (p < .001, all). At peak vertical GRF, the knee extension moment and ankle plantarflexion moment were lower in rearfoot landing than in forefoot landing (p = .003 and p < .001, respectively). From initial contact to peak vertical GRF, the negative work of the hip, knee, and ankle joint was significantly reduced during rearfoot landing (p < .001, all). The contribution to the total work of the ankle joint was the greatest during forefoot landing, whereas the contribution to the total work of the hip joint was the greatest during rearfoot landing. Conclusion: These results suggest that the energy absorption strategy was changed during rearfoot landing compared with forefoot landing according to lower-extremity joint kinematics and kinetics.

Influence of increasing knee flexion angle on knee-ankle varus stress during single-leg jump landing.

ObjectivesThe primary aim of this study was to identify the relationship between the peak knee flexion angle and knee-ankle varus stress in the landing phase of the single-leg jump during running.MethodsFifteen male handball players from the first Saudi Arabian handball team were incorporated in this study. Each player performed a single-leg jump-land after running a fixed distance of 450 cm. The data were measured using a 3D motion analysis system. The maximum knee flexion angle, knee varus angle, centre of pressure pathway in the medio-lateral direction, and ankle varus moment were measured.ResultsThe Pearson Product Moment Correlation showed that a greater knee flexion angle was related to a greater lateral displacement of the centre of pressure (r = 0.794, P = 0.000), a greater ankle varus moment (r = 0.707, P = 0.003), and a greater knee varus angle (r = 0.753, P = 0.001). In addition, the greater ankle varus moment was related to the greater lateral displacement of the centre of pressure (r = 0.734, P = 0.002).ConclusionsThese findings may help physical therapists and conditioning professionals to understand the impact of increasing knee flexion angle on the lower limb joints. Such findings may help to develop training protocols for enhancing the lateral body reaction during the landing phase of the single-leg jump, which may protect the knee and ankle joints from excessive varus stresses.

Effect of shoe insole density on impact characteristics and performance during a jump-landing task

The purpose of this study was to examine the effect of shoe insole densities on impact shock attenuation, lower extremity biomechanics and performance during a jump-landing activity. Fifteen healthy male college athletes performed three trials of jump-landings during three test conditions (soft, hard and medium insoles). Ground reaction forces (GRFs) and sagittal plane lower extremity kinematic data were sampled simultaneously. A repeated measure analysis of variance was performed on kinematic and GRF variables. The use of soft cushioned insoles during jump-landing significantly increased the mean jump height after first landing phase followed by take-off compared with medium insoles (p = 0.04). The mean vertical GRF loading rate was significantly lower with the hard cushioned insoles (p = 0.027). However, there was significantly greater knee flexion angle at initial contact in hard cushioned insoles compared with soft and medium insoles (p = 0.04). Softer shoe inserts may facilitate jump height, but, adversely increase vertical GRF loading rate. Vertical GRF loading rate decreased significantly with the use of hard cushioned insoles. These findings indicate that hard insole may provide greater cushioning during first landing followed by take-off and jumping. Results of this study support the use of hard cushioned insoles to reduce loading rates during first landing phase of a jump-landing task. Their ability to reduce landing-related injuries, however, remains in question.