Anterior Cruciate Ligament Reconstruction Limb Research Articles

Bilateral Gait 6 and 12 Months Post-Anterior Cruciate Ligament Reconstruction Compared with Controls.

To compare gait biomechanics throughout stance phase 6 and 12 months after unilateral anterior cruciate ligament reconstruction (ACLR) between ACLR and contralateral limbs and compared with controls. Vertical ground reaction force (vGRF), knee flexion angle (KFA), and internal knee extension moment (KEM) were collected bilaterally 6 and 12 months post-ACLR in 30 individuals (50% female, 22 ± 3 yr, body mass index = 23.8 ± 2.2 kg·m) and at a single time point in 30 matched uninjured controls (50% female, 22 ± 4 yr, body mass index = 23.6 ± 2.1 kg·m). Functional analyses of variance were used to evaluate the effects of limb (ACLR, contralateral, and control) and time (6 and 12 months) on biomechanical outcomes throughout stance. Compared with the uninjured controls, the ACLR group demonstrated bilaterally lesser vGRF (ACLR, 9% body weight [BW]; contralateral, 4%BW) during early stance and greater vGRF during midstance (ACLR, 5%BW; contralateral, 4%BW) 6 months post-ACLR. Compared to the uninjured controls, the ACLR group demonstrated bilaterally lesser vGRF (ACLR, 10%BW; contralateral, 8%BW) during early stance and greater vGRF during midstance (ACLR, 5%BW; contralateral, 5%BW) 12 months post-ACLR. Compared with controls, the ACLR limb demonstrated lesser KFA during early stance at 6 (2.3°) and 12 months post-ACLR (2.0°), and the contralateral limb demonstrated lesser KFA during early stance at 12 months post-ACLR (2.8°). Compared with controls, the ACLR limb demonstrated lesser KEM during early stance at both 6 months (0.011BW × height) and 12 months (0.007BW × height) post-ACLR, and the contralateral limb demonstrated lesser KEM during early stance only at 12 months (0.006BW × height). Walking biomechanics are altered bilaterally after ACLR. During the first 12 months post-ACLR, both the ACLR and contralateral limbs demonstrate biomechanical differences compared with control limbs. Differences between the contralateral and control limbs increase from 6 to 12 months post-ACLR.

Effect of Graft Type on Thigh Circumference, Knee Range of Motion, and Lower-Extremity Strength in Pediatric and Adolescent Males Following Anterior Cruciate Ligament Reconstruction.

To treat anterior cruciate ligament (ACL) injury, ACL reconstruction (ACLR) surgery is currently a standard of the care. However, effect of graft type including bone-patellar tendon-bone (BTB), hamstring tendon, or iliotibial band (ITB) on thigh size, knee range of motion (ROM), and muscle strength are understudied. To compare postoperative thigh circumference, knee ROM, and hip and thigh muscle strength in adolescent males who underwent ACLR, based on the 3 different autograft types: BTB, hamstring (HS), and ITB. Biomechanical laboratory. Male ACLR patients who are younger than 22 years of age (total N = 164). At 6- to 9-month postoperative visits, thigh circumference, knee ROM, and hip and thigh muscle strength were measured. Deficits of each variable between the uninvolved and ACLR limb were compared for pediatric and adolescent ACLR males in the BTB, HS, and ITB cohorts. Baseline characteristics, including physical demographics and meniscus tear status, were compared, and differences identified were treated as covariates and incorporated in analysis of covariance. Data were from 164 adolescent male ACLR patients [mean age 15.7 (1.2) years]. There were no statistical differences in thigh circumference, knee ROM, hip abductor, and hip-extensor strength among the 3 autografts. However, patients with BTB demonstrated 12.2% deficits in quadriceps strength compared with 0.5% surplus in HS patients (P = .002) and 1.2% deficits in ITB patients (P = .03). Patients with HS showed 31.7% deficits in hamstring strength compared with 5.4% deficits in BTB (P = .001) and 7.7% deficits in ITB (P = .001) groups at 6- to 9-month postoperative visits. Adolescent male ACLR patients with BTB and HS autografts demonstrated significant deficits in quadriceps and hamstring strength, respectively, at 6 to 9 months postoperatively. Minimal lower-extremity strength deficits were demonstrated in pediatric male ACLR patients undergoing ITB harvest.

ACL Size and Notch Width Between ACLR and Healthy Individuals: A Pilot Study.

Given the relatively high risk of contralateral anterior cruciate ligament (ACL) injury in patients with ACL reconstruction (ACLR), there is a need to understand intrinsic risk factors that may contribute to contralateral injury. The ACLR group would have smaller ACL volume and a narrower femoral notch width than healthy individuals after accounting for relevant anthropometrics. Cross-sectional study. Level 3. Magnetic resonance imaging data of the left knee were obtained from uninjured (N = 11) and unilateral ACL-reconstructed (N = 10) active, female, collegiate-level recreational athletes. ACL volume was obtained from T2-weighted images. Femoral notch width and notch width index were measured from T1-weighted images. Independent-samples t tests examined differences in all measures between healthy and ACLR participants. The ACLR group had a smaller notch width index (0.22 ± 0.02 vs 0.25 ± 0.01; P = 0.004; effect size, 1.41) and ACL volume (25.6 ± 4.0 vs 32.6 ± 8.2 mm3/(kg·m)-1; P = 0.025; effect size, 1.08) after normalizing by body size. Only after normalizing for relevant anthropometrics, the contralateral ACLR limb had smaller ACL size and narrower relative femoral notch size than healthy individuals. These findings suggest that risk factor studies of ACL size and femoral notch size should account for relevant body size when determining their association with contralateral ACL injury. The present study shows that the method of the identified intrinsic risk factors for contralateral ACL injury could be used in future clinical screening settings.

Less femoral cartilage deformation following walking associates with clinically relevant symptoms in individuals with anterior cruciate ligament reconstruction

Purpose: Approximately one-third of individuals with an anterior cruciate ligament reconstruction (ACLR) develop post-traumatic knee osteoarthritis (PTOA) within the first decade following ACLR. Currently there is a need to develop methods of early detection of PTOA, as articular cartilage damage is irreversible. Diagnostic brightness-mode (B-mode) ultrasound has been used to evaluate femoral cartilage deformation, evidenced by a decrease in cross-sectional area (CSA), following 30 minutes of treadmill walking in healthy uninjured individuals. Additionally, femoral cartilage CSA is greater in the ACLR limb compared to the uninjured limb in a resting state, which is similar to results from magnetic resonance imaging studies hypothesized to demonstrate cartilage swelling following joint injury. It remains unknown if the magnitude of femoral cartilage deformation following a standardized walking protocol is related to clinically relevant symptoms (CRS) in those with an ACLR. Persistent CRS, measured with the Knee Osteoarthritis and Injury Outcome Score (KOOS), have been reported in 39% of individuals six years following ACLR. The purpose of the current study was to determine the magnitude of femoral cartilage deformation following a standardized walking protocol which best-identified individuals with CRS. We hypothesized that individuals with this magnitude of femoral cartilage deformation would also be more likely to demonstrate CRS. Methods: Thirty-two individuals (56% female, 22±4 years old, 23.8±2.8 kg/m2body mass index, 50±37 months since ACLR) with a history of primary unilateral ACLR were recruited for a cross-sectional descriptive laboratory experiment. Femoral cartilage CSA was measured with B-mode ultrasound immediately prior to and following 3,000 steps of walking on a treadmill at a self-selected comfortable speed. Prior to the pre-walking ultrasound images, individuals rested in the long-sit position for 45 minutes to allow the cartilage rebound for a baseline CSA assessment. Individuals moved their knee into 140° of flexion to capture the anterior portion of the femur on the ultrasound during imaging. Femoral cartilage was segmented using ImageJ software, and cartilage deformation on the involved limb was calculated as a percent change (%Δ)from baseline, with negative %Δ indicating deformation following walking. All individuals were classified as symptomatic or asymptomatic based on previously defined cutoff values for the KOOS. A symptomatic individual was defined as scoring ≤ 87.5 on the quality of life portion of the KOOS as well as scoring below the cutoff of at least two other subscales of the KOOS questionnaire (KOOS Symptoms ≤ 85.7; KOOS Pain ≤ 86.1; KOOS ADL ≤ 86.8, KOOS Sports ≤ 85.0). Fourteen of the 32 individuals were classified as symptomatic. Area under the curve (AUC) values were calculated using receiver operator characteristic curve analysis to determine the capacity of femoral cartilage deformation to identify symptomatic individuals. If a significant AUC was determined (i.e. AUC 95% confidence intervals [CI] did not cross 0.5), we identified the cutoff value maximizing sensitivity and specificity. Lastly, an odds ratio was calculated to demonstrate the association between the cartilage deformation cutoff score and symptoms. Results: Femoral cartilage deformation -0.15±4.47%Δ, range: -8.18 - 13.87%Δ) displayed fair accuracy (AUC = 0.70; 95% CI, 0.51 - 0.89) for identifying symptomatic individuals. A femoral cartilage deformation cutoff of -0.29% was found to maximize sensitivity (0.79) and specificity (0.67). Individuals whose femoral cartilage did not deform by at least -0.29%Δ (meaning cartilage CSA stayed the same or increased during walking) displayed 7.33 (1.47 - 36.66) times higher odds of being symptomatic. Conclusions: Contrary to our hypothesis, individuals who did not demonstrate deformation of at least -0.29%Δ in the involved limb during 3,000 steps were more likely to report CRS. Sixteen individuals (50%) did not demonstrate deformation and experienced an increase in CSA during walking. Overall, while the mean is small and the standard deviation is large, this reflects half of participants increased CSA while the other half decreased CSA during walking. Individuals who demonstrated an increase in femoral cartilage CSA following walking were more likely to be symptomatic. Preliminary data demonstrates femoral cartilage in uninjured controls deforms (-1.33±1.65%) following 3,000 steps, which may indicate that femoral cartilage deformation is a healthy response to walking. The mechanism leading to an increase in CSA following 3,000 steps in these ACLR individuals remains unknown. It is possible increased CSA following walking is due to altered cartilage composition or aberrant biomechanics, which may promote cartilage swelling or altered fluid shifts within the tissue during movement.

Return to play following anterior cruciate ligament reconstruction: incorporating fatigue into a return to play functional battery. Part A: treadmill running

BackgroundThe risk of reinjury and other sequelae following anterior cruciate ligament reconstruction (ACLR) remains high. Lack of knowledge regarding factors contributing to these risks limits our ability to develop sensitive...

Quadriceps weakness associates with greater T1ρ relaxation time in the medial femoral articular cartilage 6months following anterior cruciate ligament reconstruction.

Quadriceps weakness following anterior cruciate ligament reconstruction (ACLR) is linked to decreased patient-reported function, altered lower extremity biomechanics and tibiofemoral joint space narrowing. It remains unknown if quadriceps weakness is associated with early deleterious changes to femoral cartilage composition that are suggestive of posttraumatic osteoarthritis development. The purpose of the cross-sectional study was to determine if quadriceps strength was associated with T1ρ relaxation times, a marker of proteoglycan density, of the articular cartilage in the medial and lateral femoral condyles 6months following ACLR. It is hypothesized that individuals with weaker quadriceps would demonstrate lesser proteoglycan density. Twenty-seven individuals (15 females, 12 males) with a patellar tendon autograft ACLR underwent isometric quadriceps strength assessments in 90°of knee flexion during a 6-month follow-up exam. Magnetic resonance images (MRI) were collected bilaterally and voxel by voxel T1ρ relaxation times were calculated using a five-image sequence and a monoexponential equation. Following image registration, the articular cartilage for the weight-bearing surfaces of the medial and lateral femoral condyles (MFC and LFC) were manually segmented and further sub-sectioned into posterior, central and anterior regions of interest (ROI) based on the corresponding meniscal anatomy viewed in the sagittal plane. Univariate linear regression models were used to determine the association between quadriceps strength and T1ρ relaxation times in the entire weight-bearing MFC and LFC, as well as the ROI in each respective limb. Lesser quadriceps strength was significantly associated with greater T1ρ relaxation times in the entire weight-bearing MFC (R2 = 0.14, P = 0.05) and the anterior-MFC ROI (R2 = 0.22, P = 0.02) of the ACLR limb. A post hoc analysis found lesser strength and greater T1ρ relaxation times were significantly associated in a subsection of participants (n = 18) without a concomitant medial tibiofemoral compartment meniscal or chondral injury in the entire weight-bearing MFC, as well as anterior-MFC and central-MFC ROI of the ACLR and uninjured limb. The association between weaker quadriceps and greater T1ρ relaxation times in the MFC suggests deficits in lower extremity muscle strength may be related to cartilage composition as early as 6months following ACLR. Maximizing quadriceps strength in the first 6months following ACLR may be critical for promoting cartilage health early following ACLR. Prognostic level 1.

Knee mechanics during a change of direction movement in division I athletes following full return to sport from anterior cruciate ligament reconstruction

ObjectivesThe objective of this study was to determine whether Division I athletes following anterior cruciate ligament reconstruction (ACLR), and who are medically cleared to return to sport, demonstrate faulty knee mechanics during a change of direction maneuver, as evidenced by the presence of genu valgum on VICON® motion analysis system of 5° or greater. Study designCross-sectional study. SettingUniversity. ParticipantsTen Division I athletes performed a 90° change of direction movement on both the ACLR and unaffected limbs. Main outcome measuresKnee mechanics were assessed using the VICON® motion analysis system. Knee position was analyzed in the frontal plane and peak genu valgum position was determined during the functional movement. ResultsEight out of ten athletes (80%) demonstrated genu valgum ≥ 5° on the ACLR limb during a 90° cutting movement. Fourteen out of twenty (70%) of the knees assessed demonstrated genu valgum ≥ 5° during a 90° cutting movement. ConclusionAthletes who have fully returned to sport following an ACLR demonstrate substantial genu valgum during a cutting maneuver, which suggests an increased risk for future injury. These results show an increased need during ACL rehabilitation to focus on existing biomechanical deficits during sport-specific movements.

Comparison of drop jump landing biomechanics and asymmetry among adolescents with hamstring, patellar and quadriceps tendon autografts for anterior cruciate ligament reconstruction

BackgroundAdolescent anterior cruciate ligament reconstruction (ACLR) commonly utilizes hamstring (HT), patellar (PT) or quadriceps (QT) tendon autografts, but consensus is lacking regarding optimal graft choice. This study compared landing biomechanics and asymmetries among ACLR patients with HT, PT and QT grafts and uninjured controls. MethodsThis retrospective study included 61 adolescents with unilateral ACLR (27 HT, 20 PT, 14 QT; four to 12 months post-surgery, mean 6.4; age 15.4, SD 1.4 years) and 27 controls (14.6, SD 0.9 years) who were evaluated during drop jump landings. Lower extremity 3D biomechanics and asymmetries were compared. ResultsCompared to controls, all operative limbs exhibited 1) greater hip flexion and lower dorsiflexion angles; 2) higher hip and lower knee and ankle flexion moments; 3) higher energy absorption at the hip (HT and QT only) and lower at the knee and ankle; and 4) higher knee abduction moments. Asymmetries observed in all ACLR groups included 1) lower knee and ankle flexion angles; 2) lower knee and ankle flexion moments; 3) lower energy absorption at the knee and ankle; and 4) higher hip and knee abduction moments on the operative side. The PT and QT groups demonstrated greater asymmetry in hip and knee flexion moments compared to HT. ConclusionsWhile adolescent ACLR limbs offloaded the knee and ankle, patients with PT or QT grafts demonstrated greater deficiencies during rehabilitation than those reconstructed with HT. Graft choice in ACLR should remain patient-specific and aim to optimize biomechanics with the ultimate goal of minimizing graft re-tear and donor site morbidity.

Association between gait mechanics and ultrasonographic measures of femoral cartilage thickness in individuals with ACL reconstruction

BackgroundIndividuals with anterior cruciate ligament reconstruction (ACLR) are at greater risk for knee osteoarthritis, which may be in part due to altered gait biomechanics. Articular cartilage thickness is typically imaged using magnetic resonance imaging, which is costly and lacks portability. Ultrasonography may provide an alternative imaging method for articular cartilage. It is unclear if ultrasonographic measurements of cartilage thickness are associated with gait biomechanics in individuals with ACLR. Research QuestionTo evaluate the association between sagittal and frontal plane knee mechanics during gait and resting femoral cartilage thickness from ultrasonography. MethodsTwenty-five females with ACLR (age = 21.7 ± 2.6 years, time since ACLR = 60.6 ± 24.8 months) completed assessments of walking biomechanics and resting femoral cartilage thickness. Linear regression examined the association between gait biomechanics and cartilage thickness at the medial (MC) and lateral (LC) femoral condyles, and intercondylar notch (IC) after accounting for time since ACLR, meniscal injury, and gait speed. ResultsIn the ACLR limb, larger vertical ground reaction force (ΔR2 = 0.21, pΔ = 0.03), knee flexion angle (ΔR2 = 0.15, pΔ = 0.05), knee flexion excursion (KFE) (ΔR2 = 0.16, pΔ = 0.04), and knee flexion impulse (KFI) (ΔR2 = 0.23, pΔ = 0.02) were associated with thicker MC cartilage. A larger knee adduction angle (ΔR2 = 0.20, pΔ = 0.03) and knee adduction moment (KAM) (ΔR2 = 0.20, pΔ = 0.03) were associated with thinner MC thickness. Larger KFE (ΔR2 = 0.20, pΔ = 0.03) was associated with thicker LC cartilage. Gait biomechanics were not associated with IC cartilage thickness. After accounting for co-variates, the combination of KFI and KAM was predictive of MC thickness (ΔR2 = 0.37, pΔ = 0.01; Total R2 = 0.52, p = 0.02). Meniscal injury, KAM, and KFI were significant predictors in the model. In the contralateral limb, KFE was associated with thicker MC cartilage (ΔR2 = 0.16, pΔ = 0.05). SignificanceSagittal and frontal plane knee mechanics during gait are uniquely associated with ultrasonographic measurements of femoral cartilage thickness in individuals with ACLR. Furthermore, concomitant medial meniscal injury was associated with thinner MC cartilage.

Walking gait asymmetries 6 months following anterior cruciate ligament reconstruction predict 12-month patient-reported outcomes.

The study sought to determine the association between gait biomechanics (vertical ground reaction force [vGRF], vGRF loading rate [vGRF-LR]) collected 6 months following anterior cruciate ligament reconstruction (ACLR) with patient-reported outcomes at 12 months following ACLR. Walking gait biomechanics and all subsections of the Knee Injury and Osteoarthritis Outcomes Score (KOOS) were collected at 6 and 12 months following ACLR, respectively, in 25 individuals with a unilateral ACLR. Peak vGRF and peak instantaneous vGRF-LR were extracted from the first 50% of the stance phase. Limb symmetry indices (LSI) were used to normalize outcomes in the ACLR limb to that of the uninjured limb (ACLR/uninjured). Linear regression analyses were used to determine associations between biomechanical outcomes and KOOS while accounting for walking speed. Receiver operator characteristic curves were used to determine the accuracy of 6-month biomechanical outcomes for identifying individuals with acceptable patient-reported outcomes, using previously defined KOOS cut-off scores, 12 months post-ACLR. Individuals with lower peak vGRF LSI 6 months post-ACLR demonstrated worse patient-reported outcomes (KOOS Pain, Activities of Daily life, Sport and Recreation, Quality of Life) at the 12-month exam. A peak vGRF LSI ≥0.99 6 months following ACLR associated with 13.33× higher odds of reporting acceptable patient-reported outcomes 12 months post-ACLR. Lesser peak vGRF LSI during walking at 6-months post-ACLR may be a critical indicator of worse future patient-reported outcomes. Clinical significance achieving early symmetrical lower extremity loading and minimizing under-loading of the ACLR limb during walking may be a potential therapeutic target for improving patient-reported outcomes post-ACLR. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:2932-2940, 2018.

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.

Lower Limb Biomechanics During Single-Leg Landings Following Anterior Cruciate Ligament Reconstruction: A Systematic Review and Meta-Analysis.

Anterior cruciate ligament reconstruction (ACLR) may not restore lower limb biomechanics during single-limb landings. Our objective was to identify and evaluate differences in lower limb biomechanics during high-demand single-limb landings between the ACLR limb and the contralateral limb and healthy control participants. A systematic review of the literature was conducted using six electronic databases searched until April 2017 for published peer-reviewed studies that investigated lower limb biomechanics on the ACLR limb compared with either the contralateral limb or those of control participants. Meta-analysis with standardized mean differences (SMD) were performed for peak angles and moments (hip, knee and ankle joints) in the sagittal plane during single-limb landing tasks. A total of 35 studies met inclusion criteria. Four different single-leg landing tasks were identified: forward hop (n = 24 studies), landing from a height (n = 9 studies), vertical hop (n = 4 studies), and diagonal leap (n = 1 study). A reduced peak knee flexion angle was found in the ACLR limb compared with the contralateral limb during a forward hop landing task (SMD - 0.39; 95% confidence interval [CI] - 0.59 to - 0.18) and compared with a control group (SMD between - 1.01 and - 0.45) for all three reported single-leg landing tasks: forward hop, landing from a height, and diagonal leap. Similarly, a reduced peak knee internal extensor moment was found in the ACLR limb compared with the contralateral limb for all three reported landing tasks: forward hop, landing from a height, vertical hop (SMD between - 1.43 and - 0.53), and in two of three landing tasks when compared with a control group (SMD between - 1.2 and - 0.52). No significant differences in peak flexion (hip and ankle) angle or peak (hip and ankle) internal extensor moment were found in the ACLR limb compared with both the contralateral limb and a control group. Participants performed single-limb landings on the ACLR limb with reductions in peak sagittal knee kinematics as well as peak joint moments compared with both the contralateral limb and a control group. Stiffer single-leg landings potentially expose the knee joint to higher forces, which may increase risk of injury. Clinical testing after ACLR surgery should explore movement quality as well as performance of functional tasks. Case-control, IV.

Lesser Mechanical Loading During Walking Gait Associates with Worse Proteoglycan Density 6 months Following Anterior Cruciate Ligament Reconstruction

Optimal mechanical loading is necessary to decrease the risk of posttraumatic osteoarthritis (PTOA) following anterior cruciate ligament reconstruction (ACLR) and lesser mechanical loading early following ACLR may increase the risk for PTOA onset. T1ρ magnetic resonance imaging (MRI) has been used to measure cartilage composition at early time points following ACLR. PURPOSE: To determine the association between proteoglycan density of femoral cartilage derived from T1ρ MRI relaxation times and peak vertical ground reaction force (vGRF) and instantaneous vGRF loading rate (vGRF-LR) during walking gait 6 months following ACLR. METHODS: Twenty-nine individuals (52% female, BMI = 24±3 kg/m2) with a unilateral patellar-tendon autograft ACLR participated in this study. Five trials of walking gait at self-selected speed were performed 6 months following ACLR. Peak vGRF and instantaneous vGRF-LR were extracted from the first 50% of the stance phase in both limbs. T1ρ relaxation times were calculated for articular cartilage in the medial and lateral condyles (MFC & LFC) by fitting a monoexponential model. The weight bearing MFC and LFC cartilage was manually segmented into posterior, central, and anterior regions of interest (ROI) based on the location of the meniscus in the sagittal plane. Affine and deformable registration techniques were used to register the ACLR limb to the uninjured limb. Inter-limb mean T1ρ relaxation time ratios (RTR = ACLR limb / uninjured limb) were calculated for each ROI. Separate, stepwise linear regressions were used to determine the unique associations between vGRF outcomes and T1ρ RTR in each ROI after accounting for walking speed and meniscal injury (ΔR2; P≤ 0.05). RESULTS: In the ACLR limb, lesser vGRF during gait was associated with lesser proteoglycan density in the posterior (ΔR2=0.22, P=0.02) and central LFC (ΔR2=0.22, P=0.02), as well as the posterior (ΔR2=0.12, P=0.05) and central MFC (ΔR2=0.21, P=0.01). vGRF-LR in the ACLR limb and all vGRF outcomes in the contralateral limb did not significantly associate with T1ρ RTR for any ROI. CONCLUSIONS: Individuals with lesser vGRF in the ACLR limb presented with T1ρ MRI findings consistent with deteriorating cartilage health. Understanding how loading affects joint health is critical to developing interventions to delay PTOA onset.

Quadriceps Strength and Landing Symmetry Following ACL Reconstruction

PURPOSE: Quadriceps strength asymmetry is common following anterior cruciate ligament reconstruction (ACLR). However, quadriceps strength symmetry may not reflect symmetry in other tasks such as a landing. The purpose of this study was to 1) examine the relationship between quadriceps strength symmetry and landing symmetry and 2) to compare landing mechanics between limbs of individuals with ACLR. METHODS: Quadriceps strength and landing biomechanics were assessed in 46 individuals with primary unilateral ACL reconstruction (34 females, age=22.0±2.8 years, height=1.70±.09m, mass=71.9±16.1kg, IKDC=86.1±9.3). Participants completed 3 drop jump landings from a 30cm height located at a distance of 50% of their height onto 2 force plates. Quadriceps strength was assessed via isometric (peak and rate of torque development (RTD)) and isokinetic knee extension at 60°, 180°, and 240°/second. Limb symmetry index (LSI) was calculated as the ratio of the involved divided by the uninvolved limb for strength and landing biomechanics (knee flexion angle (KFA) (at ground contact, peak, and excursion), peak external knee flexion moment (KFM), and vertical ground reaction force (GRF)). Pearson correlation was used to assess the relationship between quadriceps LSIs and KFM and GRF LSIs. Spearman rho was used to examine the relationship between quadriceps LSIs and KFA LSIs. Paired samples t-tests were used to compare dependent variables between limbs (α=0.05). RESULTS: Isometric strength LSI (r=0.30, p=0.05) and RTD LSI (r=0.37, p=0.01) were associated with KFM LSI. Isometric strength LSI (rho=0.34, p=0.02) and isokinetic strength LSI at 60° (rho=0.40, p=0.01) and 180° (rho=0.31, p=0.05) were associated with knee flexion excursion LSI. Isokinetic strength at 180° (r=0.39, p=0.01) was associated with GRF LSI. Uninvolved limbs had greater GRF (2.48±0.77 vs. 2.23±0.69 BW, p=0.034) and KFM (0.17±0.04 vs. 0.14±0.04 %BW*height, p<0.001) compared to involved limbs. CONCLUSIONS: ACLR limbs had smaller GRF and KFM compared to uninvolved limbs. This may indicate a compensatory strategy to underload the involved limb during landing. The weak correlations between quadriceps strength LSI and landing LSI may indicate that other factors such as impaired neuromuscular control or fear of re-injury influence landing symmetry.

Quadriceps Function Does Not Differ Between Subjects With ACL Reconstruction With Impulsive Vs. Normal Loading

Individuals with anterior cruciate ligament reconstruction (ACLR) are at a significant greater risk of knee osteoarthritis (OA). The heelstrike transient (HST) during gait is indicative of impulsive/high-rate loading, which has been implicated in cartilage degradation and knee OA development. The quadriceps attenuates loading during gait, and quadriceps dysfunction following ACLR may contribute to impulsive loading and knee OA risk. PURPOSE: To determine the differences in quadriceps function between impulsive loaders and non-impulsive loaders during walking gait. METHODS: Forty-five volunteers with unilateral ACLR participated in this study (32F, 20±3 years old, 71±19 kg, 1.7±0.1 m, 23±15 [range 7-58] months post-ACLR). Quadriceps function in the ACLR limb was quantified during maximal isometric contraction at 90° of knee flexion via the peak torque, rate of torque development (RTD) from 20% to 80% of the interval from onset to peak torque, RTD from onset to 100 ms, and RTD from 100ms to 200ms. All values were normalized to body mass. Gait biomechanics were assessed during overground walking at a self-selected pace. A trial was classified as possessing a HST if the ratio of the vertical ground reaction force peak immediately following heelstrike to the impending local minimum exceeded 1.2. Subjects were classified as “Impulsive” loaders if a HST was identified in at least 3 of 5 of trials. Independent t-tests and correlations were utilized for the analysis. RESULTS: 31% of the subjects were identified as Impulsive loaders. However, there were no significant differences between Impulsive and Normal loaders for RTD20-80% (0.41±0.46 vs. 0.42±0.44, p=0.96), RTD0-100ms (2.9±1.9 vs. 3.5±2.6, p=0.41), RTD100-200ms (2.5±1.4 vs. 2.3±1.5, p=0.62), or peak torque (2.2±0.7vs. 2.3±0.7, p=0.45). There were no significant correlations between the %trials with HST and the quadriceps function indices (r=-0.043-0.172, p=0.258-0.952). CONCLUSION: Roughly 1/3 of our subjects were identified as Impulsive loaders. This statistic mirrors the risk of knee OA development (~30%) in the first decade following ACLR. Our data suggest that this relationship is not associated with quadriceps function. Future research is necessary to determine the role of the HST in knee OA development and the factors that contribute to its presence.

Influence of hamstring activity on knee moments during loading response of gait in individuals following ACL reconstruction

Purpose: Clinically, restoration of gait mechanics following anterior cruciate ligament reconstruction (ACLr) is expected by 3 months post-surgery. However, biomechanical studies at this time consistently report the presence of reduced knee extensor moments in the surgical limb during loading response (LR). This reduction in knee loading is quantified by net joint moments (NJM) estimated using inverse dynamics and represents the minimum moment required for the given kinematics. As a result, the NJM does not consider the contribution from individual muscle groups including quadriceps and hamstrings. Thus, alterations in quadriceps or hamstrings activity could confound our interpretation of the NJM and characterization of knee loading in the surgical limb. In the presence of increased knee flexor activity, the true contribution from the knee extensors may not be reduced at all. Moreover, increased hamstring and consequential quadriceps activity could result in increased tibiofemoral compressive forces and lead to the progression of knee osteoarthritis. Thus, the purpose of this study is to compare the influence of hamstring activity on knee moments during LR between limbs in individuals post-ACLr. Methods: 17 individuals (11F, 24 ± 11 yrs) 114 ±1 7 days post-ACLr walked at 1.4 m/s. 3D kinematics (250 Hz), ground reaction forces (GRF; 1000 Hz) and anthropometrics were used to quantify sagittal plane joint kinematics and kinetics (inverse dynamics). Medial and lateral hamstring surface electromyography (EMG; 1000 Hz) was collected. Maximum voluntary isometric contractions (MVIC) were performed bilaterally. Raw EMG signals were band-pass filtered (10–500 Hz) and rectified. A 6 Hz low-pass filter was used to create a linear envelope. All data were normalized to 101 points of stance. A standard musculoskeletal SIMM (Software for Interactive Musculoskeletal Modeling) model was used to estimate knee flexor moments. Sagittal plane hip, knee, and ankle kinematics and hamstring EMG (biceps femoris long head, BFLH, and short head, BFSH, semimembranosus, SM, and semitendinosus, ST) normalized to MVIC were used as inputs. SM and BFSH activation were assumed to be the same as ST and BFLH, respectively. To account for differences in hamstring strength, the knee flexor moment from SIMM was scaled using a ratio of the subject’s maximum knee flexor torque during MVIC divided by the maximum knee flexor torque of the SIMM model in the testing position. The sum of the scaled estimated knee flexor moment and net knee moment (Visual3D) were used to estimate knee extensor torque. Moment impulses were calculated as the area under the curve from initial contact to peak knee flexion. Four successful trials were collected for the surgical (ACLr) and non-surgical (NS) limbs. Paired sample t-tests were used to compare net knee and estimated flexor and extensor moment impulses between limbs (mean ± SE); α = 0.05. Results: Net knee (P = 0.02; ACLr: −0.028 ± 0.003; NS: −0.041 ± 0.004 Nm*s/kg) and estimated extensor (P = 0.02; ACLr: −0.035 ± 0.004; NS: −0.048 ± 0.005 Nm*s/kg) moment impulses during LR were reduced in ACLr compared to NS limb. However, estimated knee flexor moment impulse (P = 0.99; ACLr:0.008 ± 0.001; NS:0.008 ± 0.001 Nm*s/kg) was not different. Conclusions: These data are consistent with the literature reporting reduced net knee loading in the surgical limb post-ACLr. When accounting for the torque-producing capabilities of the knee flexors, the estimated knee extensor moment was greater than the net moment in both limbs. The estimated knee extensor moment remained reduced in the ACLr limb compared to the NS limb in the absence of between limbs differences in SIMM estimated knee flexor moment. These data indicate that individuals do not disproportionately increase hamstring contribution to the net knee moment in the surgical knee during gait and the reduced net knee moment reflects a pattern in which the contribution of knee extensors is reduced during LR of gait.

Marked asymmetry in vertical force (but not contact times) during running in ACL reconstructed athletes

ObjectivesCompare maximum plantar force (Fmax) during running in soccer players following anterior cruciate ligament reconstruction (ACLR) as they pass return to sport (RTS) criteria. DesignCase control study. MethodsSoccer players after ACLR (n=16) and matched healthy controls (n=16) ran on a treadmill at 12, 14 and 16km/h while plantar loading data was measured using an in-shoe pressure system (Pedar-X, Novel). Fmax and contact time of the injured and uninjured limbs in athletes <9months post-ACLR and those ≥9months ACLR were compared to healthy players (no ACLR). ResultsSignificant differences with large effect sizes in Fmax asymmetry were seen at all running speeds for the athletes <9months ACLR compared to those ≥9months, and the healthy subjects. Fmax difference peaked at 16km/h; 32±11%BW in <9months ACLR group compared to 6±5%BW in ≥9months group; ES=1.67, p<0.01. There was a non-significant trend for increasing asymmetry with increasing speed for subjects who were <9months after ACLR while the reverse was true for those ≥9 months and the healthy subjects. ConclusionsRelatively large unloading of the ACLR limb (but not differences in contact times) are seen during running for athletes <9months post-ACLR despite having completed functional criteria required to permit RTS training. These asymmetries appear to slightly increase with increasing speed, and the reverse is true for healthy controls and those ≥9months after ACLR surgery.

Effect of Graft Type on Balance and Hop Tests in Adolescent Males Following Anterior Cruciate Ligament Reconstruction.

Context: Recent epidemiology studies indicated a steady increase of anterior cruciate ligament (ACL) injury in young athletes. ACL reconstruction (ACLR) is currently a standard of care, but the effect of ACLR graft including bone patellar tendon bone (BTB), hamstring tendon (HT), or iliotibial band (ITB) on balance and hop performance is understudied. Objective: To compare balance and hop deficits between uninvolved and reconstructed limbs in each autograft type (aim 1) and among the 3 autograft groups (aim 2). Setting: Biomechanical laboratory. Participants: Male ACLR patients who are younger than 22 years (total N = 160; BTB: N = 19, HT: N = 108, ITB: N = 33). Intervention: Approximately 6 to 9 months following ACLR, Y-balance and 4 types of hop tests were measured bilaterally. Main Outcome Measures: Limb symmetry index of balance and hop tests within each graft type and between the 3 graft types. Results: In the BTB group, significant anterior reach, single hop, triple hops, and cross-over hops deficits were observed on the ACLR limb compared with the uninvolved limb. The HT group showed significant deficits in single hop, triple hops, and cross-over hops on the ACLR limb relative to the uninvolved limb. Compared with the uninvolved limb, significantly decreased triple hops and 6-m timed hop deficits in the ACLR limb were recorded in the ITB group. When controlling for confounders and comparing among the 3 autograft types, the only significant difference was anterior reach, in which the BTB group showed significant deficits. Conclusion: Compared with the uninvolved limb, significant hop deficits in ACLR limb were prevalent among adolescent ACLR at ∼6 to 9 months postoperatively. After controlling covariates, significantly reduced anterior reach balance was found in the BTB group compared with the HT and ITB groups.

Knee Extensor Strength is Associated with Femoral Cartilage Thickness in Individuals with ACL Reconstruction

PURPOSE: To (1) determine the relationship between quadriceps function and femoral cartilage morphology in individuals with anterior cruciate ligament reconstruction (ACLR), and (2) compare quadriceps function and femoral cartilage morphology between injured and uninjured limbs. METHODS: Quadriceps function and femoral cartilage was assessed with unilateral ACLR in 20 subjects (women=15, age= 22.3±3.3years, time since ACLR=44.9±32.8 months). Quadriceps function was assessed using peak isometric knee extension torque (PT) and rate of torque development (RTD) at 45 degrees of knee flexion, and peak isokinetic knee extensor torque at 60, 180 and 240°/sec. Femoral cartilage morphology (area and thickness) were obtained via ultrasound imaging at 140° of knee flexion. Partial correlations were used to evaluate the associations between indices of quadriceps function, and cartilage area and thickness accounting for time since reconstruction. Paired samples t-test were used to evaluate interlimb differences. RESULTS: The ACLR limb produced smaller isometric peak torque (2.56±0.42 vs. 2.75±0.30 Nm/kg, p=0.04), slower isometric rate of torque development (38.12±13.27 vs. 47.81±17.99 Nm/sec/kg, p=0.03), and isokinetic peak knee extensor torque at 60°/sec (2.38±0.54 vs. 2.80±0.63 Nm/kg, p≤0.01) compared to the uninjured limb. No differences were found in isokinetic peak torque at 180 or 240°/sec (p=0.06 and 0.60, respectively). After accounting for time since ACLR, a positive association was found between isometric peak torque and medial femoral cartilage thickness (r=0.41, p=0.04). CONCLUSIONS: The ACLR limb demonstrated deficits in quadriceps function. We found a moderate association between isometric peak torque and medial femoral cartilage thickness. Our results suggest that restoring quadriceps strength may delay femoral cartilage thinning following ACLR.

Quadriceps Function is Associated with Running Kinetics Post Anterior Cruciate Ligament Reconstruction

PURPOSE: Individuals with anterior cruciate ligament reconstruction (ACLR) are at greater risk for knee osteoarthritis (KOA), partially due to chronic quadriceps dysfunction. Impaired quadriceps function contributes to higher loading rates during gait, and may exacerbate cartilage breakdown. The purpose of this study was to examine the association between indices of quadriceps function and ground reaction forces (GRF) characteristics linked to KOA development during running in individuals with ACLR. METHODS: Quadriceps function and running biomechanics were assessed in 20 individuals (5 M, 15 F) with unilateral ACLR (age=22.3±3.3 years, height=1.73±0.09m; mass=71.8±15.3kg). Indices of quadriceps function included isometric peak torque (PT) and rate of torque development (RTD), and isokinetic peak torque measured at 180°/s and 240°/s. Kinetic data included peak vertical impact force (PIF), average vertical loading rate (ALR), and instantaneous vertical loading rate (ILR) acquired from the ACLR limb while running at a self-selected pace. Partial correlations were used to assess the relationship between quadriceps function and running kinetics after accounting for self-selected running speed. RESULTS: Quadriceps RTD was negatively correlated with PIF (r=-0.40, p=0.04) and ALR (r=-0.48, p=0.03). A trend was observed between quadriceps RTD and ILR (r=-0.36, p=0.07). Neither isometric PT nor isokinetic PT at 180°/second or 240°/second were associated with any running biomechanics variable. CONCLUSIONS: Slower quadriceps RTD were associated with larger PIF and ALR during running. The ability of the quadriceps to generate rapid force prior to heel contact is necessary for GRF attenuation during gait. Since larger PIF and ALR have been linked to cartilage degradation in individuals with knee pathologies, the current results emphasize the role of quadriceps dysfunction in KOA development following ACLR. Improving quadriceps RTD may reduce loading characteristics that negatively influence cartilage health.