In vivo kinematics of anterior cruciate ligament deficient knees during pivot and squat activities

Background

Knee kinematics during pivoting activities are not well studied, but might provide insight critical to understanding the pathology of the anterior cruciate ligament deficient knee. The purpose of this study was to compare in vivo kinematics during weight bearing pivot and squat activities in patients with unilateral anterior cruciate ligament deficient knees, and to contrast those kinematics with the uninjured contralateral knees.

Methods

Eight unilateral anterior cruciate ligament deficient patients with a mean age of 41 (SD 7) years were enrolled. Anterior cruciate injury was confirmed by positive Lachman test and MRI. Lateral fluoroscopic images of pivot and squat activities were recorded for both anterior cruciate ligament deficient and contralateral knees. Three-dimensional tibiofemoral kinematics and centers of rotation for each knee were determined using 3D–2D model registration techniques.

Findings

During pivoting, the tibia of the anterior cruciate ligament deficient knee was significantly more anterior than the contralateral knee during tibial neutral to internal rotation. The pivot activity showed lateral centers of rotation in both anterior cruciate ligament deficient and contralateral knees while squatting showed medial centers of rotation.

Interpretation

This dynamic method might be useful to objectively characterize restoration of dynamic function in knees with various types of anterior cruciate ligament reconstructions. These results also indicate kinematics during squatting type activities cannot be extrapolated to predict knee kinematics during pivoting types of activities.     

Tibial rotation in anterior cruciate ligament reconstructed knees during single limb hop and drop landings

Background

Alterations in knee joint kinematics have been suggested as a potential mechanism that influences the development of osteoarthritis of the knee after anterior cruciate ligament reconstruction. Whilst previous work has shown changes in internal–external tibial rotation during level walking, many patients aim to return to high impact activities following surgery. This study examined tibial rotation during single limb hop and drop landings in anterior cruciate ligament reconstructed knees compared to a control group, and also evaluated the influence of graft type (hamstring or patellar tendon).

Methods

In 48 participants (17 patellar tendon graft, 18 hamstring graft and 13 controls) internal–external rotation was measured during single limb hop and drop landings in a gait laboratory at mean of 10 months after surgery.

Findings

There was no difference between the two graft types and both patient groups had less internal rotation when compared to the control group. For 60% of patients, internal rotation values were at least 5°  less than the control group mean.

Interpretation

Anterior cruciate ligament reconstructed knees with both hamstring tendon and patellar tendon grafts show altered rotational kinematic patterns during high impact dynamic load activities.     

Double-bundle ACL surgery demonstrates superior rotational kinematics to single-bundle technique during dynamic task

Background

While traditional surgical repair of the anterior cruciate ligament is able to restore anterior–posterior knee stability, laxity in the transverse plane remains. Double-bundle reconstruction has demonstrated greater rotational restraint than the single-bundle technique under passive loading conditions; however, no comparison has been made under physiological weight-bearing conditions. The purpose of this study was to determine differences in rotational knee kinematics during a dynamic task in patients who had received either a single- or double-bundle reconstruction.

Methods

Twenty-two patients exhibiting isolated anterior cruciate ligament rupture were randomly allocated either a single or double-bundle reconstruction. Three-dimensional knee kinematics were measured during a dynamic cutting activity prior to and following surgery. Functional range of rotation was compared between groups pre- and post-operatively and kinematics were assessed against uninjured control subjects.

Findings

No difference in overall range of rotation was found under physiological loading conditions. However, a significant interaction of the midpoint of the range of movement was observed; a greater external rotational shift in the single-bundle group followed reconstruction, while the kinematics of the double-bundle patient group shifted closer to those of the control group.

Interpretation

The double-bundle reconstruction demonstrated superior outcome in rotational kinematics to the single-bundle technique.     

Alterations in joint kinematics during walking following hamstring and patellar tendon anterior cruciate ligament reconstruction surgery

Background

Previous research has shown that patients with anterior cruciate ligament reconstruction have altered movement patterns in the reconstructed knee during walking. In the sagittal plane, graft specific changes in knee joint motion have been reported between hamstring and patellar tendon anterior cruciate ligament reconstruction grafts. This study examined the secondary planes of movement during walking in anterior cruciate ligament reconstructed knees to evaluate the influences of graft type (hamstring or patellar tendon) and control condition (control group or contralateral knee).

Methods

In 54 participants (18 patellar tendon graft, 18 hamstring graft and 18 controls) varus–valgus and internal–external rotation was measured during level walking in a gait laboratory at mean of 10 months after surgery. All patients had undergone primary unilateral anterior cruciate ligament reconstruction within 12 months of injury.

Findings

For internal–external rotation there was no difference between the graft types and both patient groups had reduced internal rotation (an external rotation offset) and reduced internal rotation range when compared to the control group and contralateral knee. For 31 of 36 patients, internal rotation values were less than the control group mean. The hamstring group had reduced varus rotation compared to both the patellar tendon and control groups, but not when compared to the contralateral knee.

Interpretation

The results show that there are differences in tibial rotation during walking in anterior cruciate ligament reconstructed knees compared to both the contralateral knee and uninjured control group. These kinematic alterations may relate to the high incidence of knee osteoarthritis observed in this population over time. Reduced varus in the hamstring group may relate to the graft harvest.     

An implant-free double-bundle reconstruction of the anterior cruciate ligament: operative technique and influence on tibiofemoral kinematics

Background

Reconstruction of the anterior cruciate ligament is a standard surgical procedure in sports traumatology. The widespread replacement method using hamstring tendons has an important shortcoming namely delayed or missing bony healing in contrast to patellar tendon grafts where implant-free fixation is established by using the adjacent bone blocks. The purpose of this study was to describe a new implant-free surgical procedure using hamstring tendon grafts and to analyse the influence on tibiofemoral kinematics in vitro.

Methods

Nine human knee specimens with arthroscopically transected anterior cruciate ligaments were mounted on a dynamic knee simulator and weight-bearing muscle-loaded knee flexions were simulated while a robotic universal force sensor system was used to provide external tibial loads. Three different loading conditions were simulated including partial body weight only, an additional 50 N anterior tibial force or an additional Five Nm of internal rotational torque. After reconstruction of the anterior cruciate ligament using a tibial bone block hybrid technique these three trials were repeated. The kinematics was measured with an ultrasonic measuring system and different loading and ligament conditions were examined. Graft tunnel placement was verified by computed tomography.

Findings

Our fixation method achieved stability to anterior tibial drawer force whereas internal tibial rotation did not change before and after the reconstruction. Computed tomography confirmed anatomical graft and tunnel placement.

Interpretation

The presented operative procedure is technically feasible and leads to reproducible results concerning knee joint kinematics and graft placement.     

Timing sequence of multi-planar knee kinematics revealed by physiologic cadaveric simulation of landing: Implications for ACL injury mechanism

Background

Challenges in accurate, in vivo quantification of multi-planar knee kinematics and relevant timing sequence during high-risk injurious tasks pose challenges in understanding the relative contributions of joint loads in non-contact injury mechanisms. Biomechanical testing on human cadaveric tissue, if properly designed, offers a practical means to evaluate joint biomechanics and injury mechanisms. This study seeks to investigate the detailed interactions between tibiofemoral joint multi-planar kinematics and anterior cruciate ligament strain in a cadaveric model of landing using a validated physiologic drop-stand apparatus.

Methods

Sixteen instrumented cadaveric legs, mean 45(SD 7) years (8 female and 8 male) were tested. Event timing sequence, change in tibiofemoral kinematics (position, angular velocity and linear acceleration) and change in anterior cruciate ligament strain were quantified.

Findings

The proposed cadaveric model demonstrated similar tibiofemoral kinematics/kinetics as reported measurements obtained from in vivo studies. While knee flexion, anterior tibial translation, knee abduction and increased anterior cruciate ligament strain initiated and reached maximum values almost simultaneously, internal tibial rotation initiated and peaked significantly later (P < 0.015 for all comparisons). Further, internal tibial rotation reached mean 1.8(SD 2.5)°, almost 63% of its maximum value, at the time that peak anterior cruciate ligament strain occurred, while both anterior tibial translation and knee abduction had already reached their peaks.

Interpretation

Together, these findings indicate that although internal tibial rotation contributes to increased anterior cruciate ligament strain, it is secondary to knee abduction and anterior tibial translation in its effect on anterior cruciate ligament strain and potential risk of injury.     

Biomechanical evaluation of double bundle augmentation of posterior cruciate ligament using finite element analysis

Background

Posterior cruciate ligament injuries commonly occur during sports activities or motor vehicle accidents. However, there is no previous comparison study of single bundle reconstruction, double bundle reconstruction, and double bundle augmentation with respect to biomechanical characteristics such as stability and ligament stress.

Methods

A three-dimensional finite element model of a lower extremity including femur, tibia, cartilage, meniscus, collagen fibers, and four major ligaments was developed and validated. In addition to the intact, posterior cruciate ligament injured, single bundle reconstruction, double bundle reconstruction, and double bundle augmentation models were developed. Then, the posterior and rotational tibial translations as well as the ligament stresses were predicted for 89 N posterior force and 3 Nm internal torque, respectively, in the normal (no secondary deficiency) and the secondary deficiency cases using finite element analysis.

Findings

The posterior stability and ligament stresses following double bundle augmentation were superior to those of single and double bundle reconstructions, especially after secondary deficiency in the reconstructed grafts, despite little difference in posterior stability between double bundle reconstruction and augmentation in the normal case. Similarly, the double bundle augmentation had the greatest rotational stability while there was little advantage in ligament stress compared to those of the other reconstruction method.

Interpretation

Double bundle augmentation has advantages with regard to posterior and rotational stabilities as well as ligament stress in comparison with other reconstruction methods, especially following secondary deficiencies in the reconstructed grafts.     

Knee mechanics during landing in anterior cruciate ligament patients: A longitudinal study from pre- to 12 months post-reconstruction

Background

Patients with a history of anterior cruciate ligament rupture are at elevated risk of developing knee osteoarthritis. Altered knee kinematics and kinetics during functional activities have been viewed as risk factors for cartilage breakdown and, therefore, one of the primary goals of anterior cruciate ligament reconstruction is to restore knee joint function.

Methods

Patients' (n = 18) knee mechanics while performing a single leg hop for distance were calculated for both legs using a soft-tissue artifact optimized rigid lower-body model at the pre-reconstruction state and six and twelve months after anterior cruciate ligament reconstruction.

Findings

Independent of the analyzed time point the involved leg showed a lower external flexion and adduction moment at the knee, and an increased anterior translation and external rotational offset of the shank with respect to the thigh compared to the uninvolved leg. There were no differences for any of the analyzed knee kinematic and kinetic parameters within the control subject group.

Interpretation

The identified kinematic changes can cause a shift in the normal load-bearing regions of the knee and may support the view that the risk of developing knee osteoarthritis in an anterior cruciate ligament ruptured joint while performing activities involving frequent landing and stopping actions is less likely to be associated with the knee adduction moment and is rather due to kinematic changes. Anterior cruciate ligament reconstruction surgery failed to restore normal knee kinematics during landing, potentially explaining the persistent risk for the development of knee osteoarthritis in patients who have returned to sports following reconstruction surgery.     

Effect of lower limb dominance on knee joint kinematics after anterior cruciate ligament reconstruction

Background

Normal ambulatory kinematics of the knee joint is often not fully restored after anterior cruciate ligament reconstruction, which may increase the risk for cartilage degeneration and premature osteoarthritis in the involved knees. Lower limb dominance may have impacts on knee joint kinematics after anterior cruciate ligament reconstruction, which may lead to a different prevalence of cartilage degeneration. This study aimed to evaluate the knee joint kinematics among patients with reconstruction on the dominant and non-dominant side.

Methods

Forty-one subjects with unilateral anterior cruciate ligament reconstruction (19 dominant, 22 non-dominant) were recruited after being discharged from rehabilitation programs. Twenty healthy subjects were recruited as the control group. Six degrees-of-freedom tibiofemoral motion during level walking was determined using a redundant point cluster-based marker set. Tibiofemoral joint motion and its bilateral differences were compared within each group and between groups.

Findings

The non-dominant reconstructed knees had less extension compared to their contralateral knees at heel strike and during middle stance phase (P = 0.02); whereas, the dominant reconstructed knees exhibited significantly reduced varus rotation (− 2.1° on mean, P = 0.027) and internal tibial rotation (P = 0.034) compared to their contralateral knees during both stance and swing phases.

Interpretation

The results show that different kinematics has been developed between the involved dominant and non-dominant knees after anterior cruciate ligament reconstruction, especially the secondary rotations. The differences are consistent with the unequal prevalence of cartilage degeneration in the knee joint. The findings demonstrated that the lower limb dominance had a significant effect on post-surgery knee kinematics.     

Knee rotational laxity: an investigation of bilateral asymmetry for comparison with the contralateral uninjured knee

Background

Instability associated with anterior cruciate ligament injury is commonly evaluated against the patient's contralateral knee. The objectives of this study were, therefore, to assess symmetry of rotational knee laxity in vivo under passive torsional loading in uninjured subjects, and to compare mean rotation of this control group with the contralateral, intact knees of anterior cruciate ligament deficient patients.

Methods

Axial knee rotation was measured in 29 patients with unilateral anterior cruciate ligament injury and 15 uninjured age and gender-matched control subjects using an imaging-compatible torsional loading device. Side-to-side differences in internal, external, and range of knee rotation were assessed in the control group and mean bilateral knee rotation was compared to the patients' contralateral knee data at both full extension and 30° of flexion.

Findings

Statistically significant differences in symmetry were found in three of the six measures of transverse plane rotation in the uninjured knees; a mean side-to-side difference of 2.2° in range of rotation was detected in the flexed position. No significant differences were observed between the mean values of the healthy control group and the contralateral knees of the anterior cruciate ligament deficient patients.

Interpretation

Bilateral asymmetry of rotational laxity occurs in healthy individuals. Nevertheless, comparability of rotational knee laxity between the contralateral limbs of patients and the uninjured population was evidence that rotational laxity was not inherent or developed in the contralateral knees of the anterior cruciate ligament deficient participants.     

Increasing posterior tibial slope does not raise anterior cruciate ligament strain but decreases tibial rotation ability

Background

It was investigated whether the strain of the anterior cruciate ligament and tibial kinematics are affected by increasing posterior tibial slope.

Methods

9 human cadaveric knee joints were passively moved between full extension and 120° flexion in a motion and loading simulator under various loading conditions and at 0°, 5°, 10° and 15° posterior tibial slope angles. The anterior cruciate ligament strain and the tibial rotation angle were registered. To assess the influence of posterior tibial slope on the anterior cruciate ligament strain at a fixed flexion angle the anterior cruciate ligament strain was recorded at three different flexion angles of 0°, 30° and 90° while continuously increasing the osteotomy angle from 5° to 15°.

Findings

The anterior cruciate ligament strain was either not affected by the posterior tibial slope angle or, in some load cases, was decreased for increasing posterior tibial slope (P < 0.05). There was a significant decrease of tibial rotation when the posterior tibial slope was increased to 15° for many of the load cases tested (P < 0.05). The mean maximum decrease was from 17.4° (SD 5.7°) to 11.2° (SD 4.7°) observed for flexion-extension motion under 30 N axial load in combination with an internal rotation moment.

Interpretation

The hypothesis that increasing posterior tibial slope results in higher anterior cruciate ligament strain was not confirmed. However, knee kinematics were affected in terms of a reduced tibial rotation. From a biomechanical point of view the data do not support the efficacy of sagittal osteotomies as performed to stabilize anterior cruciate ligament deficient knees.     

Effect of muscle loads and torque applied to the tibia on the strain behavior of the anterior cruciate ligament: an in vitro investigation

Background

Very little is known about the effects of applied torque about the long axis of the tibia in combination with muscle loads on anterior cruciate ligament biomechanics. The purpose of this study was to determine the effect of muscle contraction and tibial torques applied about the long axis of the tibia on anterior cruciate ligament strain behavior.

Methods

Six cadaver knee specimens were used to measure the strain behavior of the anterior cruciate ligament. Internal and external axial torques were applied to the tibia when the knee was between 30° and 120° of flexion in combination with the conditions of no muscle load, isolated quadriceps load, and simultaneous quadriceps and hamstring loading.

Findings

The highest anterior cruciate ligament strain values were measured when the muscles were not loaded, when the knee was at 120° of flexion, and when internal tibial torques were applied to the knee. During muscle loading the highest anterior cruciate ligament strain values were measured at 30° of flexion and then the strain values gradually decreased with increase in knee flexion. During co-contraction of the quadriceps and hamstring muscles the anterior cruciate ligament was unstrained or minimally strained at 60°, 90° and 120° of knee flexion.

Interpretation

This study suggests that quadriceps and hamstring muscle co-contraction has a potential role in reducing the anterior cruciate ligament strain values when the knee is in deep flexion. These results can be used to gain insight into anterior cruciate ligament injury mechanisms and to design rehabilitation regimens.     

In vivo deep-flexion kinematics in patients with posterior-cruciate retaining and anterior-cruciate substituting total knee arthroplasty

Background

Posterior-cruciate ligament retaining total knee arthroplasty designs have long been used with excellent clinical success, but often have shown kinematics and flexion performance that are significantly different from the natural knee. The purpose of this study was to compare deep-flexion knee kinematics in patients with two types of posterior-cruciate ligament retaining total knee arthroplasty.

Methods

One group received a traditional curved symmetric articular configuration, and one group received a design incorporating a lateral compartment which constrains the lateral condyle to the antero-posterior center of the tibial plateau in extension, but allows translation in flexion – roughly approximating the role of the anterior cruciate ligament. In vivo kinematics were analyzed using three-dimensional model registration and plain radiographs of kneeling and squatting activities in 20 knees in 18 patients.

Findings

Knees with the anterior cruciate ligament substituting design exhibited greater flexion, femoral antero-posterior translation and tibial internal rotation.

Interpretation

Geometric features intended to improve knee flexion, including greater antero-posterior stability, a more posterior tibial sulcus, and reshaped femoral condyles, do provide measurable and significant differences in deep-flexion knee kinematics.     

Alterations in patellofemoral kinematics following vastus medialis transection in the anterior cruciate ligament deficient rabbit knee

Background

Anterior cruciate ligament deficiency and quadriceps muscle weakness are considered to be important risk factors for aberrant patellar tracking and subsequent patellofemoral osteoarthritis. However, data from in vivo experiments looking at dynamic patellar joint kinematics and muscle force are scarce. Therefore, the purpose of this study was to evaluate the effects of anterior cruciate ligament transection and loss of vastus medialis force on patellar tracking in the rabbit knee in vivo.

Methods

Eight skeletally mature New Zealand White Rabbits, weighing 6.0 kg (0.6 kg standard deviation) were used. The experimental trials consisted of active, concentric and eccentric movements of the knee joint. Measurements were performed with the intact, the anterior cruciate ligament deficient, and the vastus medialis transected knee. Patellofemoral kinematics (shift, rotation) were quantified from high speed video.

Findings

Following anterior cruciate ligament transection, patellar tracking occurred more laterally, and caused a significant lateral rotation of the patella. The addition of vastus medialis transection did not alter patellar tracking or rotation significantly for any of the force-matched experimental conditions.

Interpretation

The loss of the anterior cruciate ligament results in lateral patellar shift and rotation while the loss of vastus medialis muscle force does not affect patellar tracking or rotation in the anterior cruciate ligament deficient knee. We suggest that the current results should be considered carefully in future interpretations of knee extensor imbalance. More research is needed to describe the contribution of vastus medialis muscle strength to medial patellofemoral stability and confirm these results in the human knee.     

Kinematic evaluation of the step-up exercise in anterior cruciate ligament deficiency

Background

Step-up exercise is one of the most commonly utilized exercises during rehabilitation of patients after both anterior cruciate ligament (ACL) injury and reconstruction. Currently, insurance providers increasingly required a trial of intensified rehabilitation before surgical reconstruction is attempted. The purpose of this study was to investigate whether this “safe” rehabilitation exercise in the setting of ACL deficiency can cause altered knee kinematics.

Methods

Thirty patients with unilateral ACL rupture were recruited for this study. The mean time from injury was 3.3 months. Tibiofemoral kinematics were determined during a step-up exercise using a combination of magnetic resonance imaging (MRI), dual fluoroscopy and advanced computer modeling.

Findings

The ACL-injured knee displayed an average 5° greater external tibial rotation than the uninjured knee (P < 0.05), during the last 30% of step-up. The ACL-injured knee also demonstrated on average 2.5 mm greater anterior tibial shift during the last 40% of stance phase (P < 0.01). In addition, during the last 30% of stance the tibia of the ACL-deficient knee tended to shift more medially (~ 1 mm) as the knee approached full extension (P < 0.01).

Interpretation

The data confirmed the initial hypothesis as it was found that ACL deficient knees demonstrated significantly increased anterior tibial translation, medial tibial translation and external tibial rotation toward the end of the step-up as the knee approached full extension. Intensive rehabilitation utilizing the step-up exercise in the setting of ACL deficiency can potentially introduce repetitive microtrauma by way of altered kinematics.     

Effect of an anterior-sloped brace joint on anterior tibial translation and axial tibial rotation: A motion analysis study

Background

Anterior tibial translation and axial tibial rotation are major biomechanical factors involved in anterior cruciate ligament injuries. This study sought to evaluate a brace prototype designed with an anterior-sloped joint, in terms of its efficacy in attenuating anterior tibial translation and axial tibial rotation during landing, using a motion analysis approach.

Methods

Ten healthy male subjects performed single-leg landing tasks from a 0.6-m height with and without the brace prototype. Ground reaction force and kinematics data were obtained using a motion-capture system and force-plates. Anterior tibial translation and axial tibial rotation were determined based on tibial and femoral marker reference frames. Vertical and anterior–posterior ground reaction forces, hip, knee and ankle joint range-of-motions and angular velocities, anterior tibial translation and axial tibial rotation were compared between unbraced and braced conditions using Wilcoxon signed-rank test.

Findings

We found no significant difference in peak vertical and anterior–posterior ground reaction forces (p = 0.770 and p = 0.332 respectively) between unbraced and braced conditions. Knee joint range-of-motion and angular velocity were lower (p = 0.037 and p = 0.038 respectively) for braced condition than unbraced condition. Anterior tibial translation and axial tibial rotation were reduced (p = 0.027 and p = 0.006 respectively) in braced condition, compared to unbraced condition.

Interpretation

The anterior-sloped brace joint helps to attenuate anterior tibial translation and axial tibial rotation present in the knee joint during landing. It is necessary to test the brace prototype in a sporting population with realistic sports landing situations in order to assess its effectiveness in lowering anterior cruciate ligament injury risk.     

Anterolaterale Rotationsinstabilität

Background

Anterolateral rotatory instability (ALRI) of the knee consists of a translational and rotational component. It is widely accepted that anterior cruciate ligament (ACL) deficiency causes anterior tibial translation, but controversy exists regarding the peripheral structures restraining tibial internal rotation. These structures may be reconstructed using lateral extra-articular soft-tissue reconstruction. The principal behind these types of reconstruction is to tether the graft posterior to the transverse center of rotation, therefore, limiting internal tibial rotation and ultimately restraining the rotational component of the pivot shift test.

Aim

The aim of the following paper is to provide a critical literature review regarding anatomy, biomechanics, and related types of reconstruction of the anterolateral side of the knee.

Materials and methods

The article provides a critical review of the ALRI literature and takes into account the authors’ own anatomical and biomechanical observations.

Results

Based on this literature review, the anterolateral structures of the knee may be more important in restraining internal tibial rotation than previously thought.

Conclusion

A combined intra-articular ACL and lateral extra-articular soft-tissue reconstruction may be desirable in revision ACL surgery and in patients presenting excessive ALRI following ACL rupture.     

Relationship of knee shear force and extensor moment on knee translations in females performing drop landings: a biplane fluoroscopy study

Background

Research has linked knee extensor moment and knee shear force to the non-contact anterior cruciate ligament injury during the landing motion. However, how these biomechanical performance factors relate to knee translations in vivo is not known as knee translations cannot be obtained with traditional motion capture techniques. The purpose of this study was to combine traditional motion capture with high-speed, biplane fluoroscopy imaging to determine relationships between knee extensor moment and knee shear force profiles with anterior and lateral tibial translations occurring during drop landing in female athletes.

Methods

15 females performed drop landings from a height of 40 cm while being recorded using a high speed, biplane fluoroscopy system and simultaneously being recorded using surface marker motion capture techniques to estimate knee joint angle, reaction force and moment profiles.

Findings

No significant statistical relationships were observed between peak anterior or posterior knee shear force and peak anterior and lateral tibial translations; or, between peak knee extensor moment and peak anterior and lateral tibial translations. Although differences were noted in peak shear force (P = 0.02) and peak knee extensor moment (P < 0.001) after stratification into low and high shear force and moment cohorts, no differences were noted in anterior and lateral tibial translations (all P ≥ 0.18).

Interpretation

Females exhibiting high knee extensor moment and knee shear force during drop landings do not yield correspondingly high anterior and lateral tibial translations.     

Reduced hamstring strength increases anterior cruciate ligament loading during anticipated sidestep cutting

Background

Dynamic knee stability is considered a critical factor in reducing anterior cruciate ligament loads. While the relationships between hamstring force production and anterior cruciate ligament loading are well known in vitro, the influence of hamstring strength to anterior cruciate ligament loading during athletic maneuvers remains unknown. Therefore, the purpose of this study was to determine the influence of hamstring strength on anterior cruciate ligament loading during anticipated sidestep cut.

Methods

Seventeen recreationally active females were recruited to perform sidestep cutting maneuvers pre/post an acute hamstring strength reduction protocol. Kinematics and kinetics were calculated during the cut and a musculoskeletal model was used to estimate muscle, joint, and anterior cruciate ligament loads. Dependent t-tests were conducted to investigate differences between the two cutting conditions.

Findings

Anterior cruciate ligament loading increased by 36% due to reduced hamstring strength. This was mostly due to a 44% increase in sagittal plane loading and a 24% increase in frontal plane loading. Post strength reduction sidestep cuts were also performed with decreased anterior tibiofemoral shear force, an outcome that would theoretically reduce anterior cruciate ligament loading. However, the overall decrease in hamstring force production coupled with a more axial hamstring line of action yielded a net increase in anterior cruciate ligament loading.

Interpretation

These results suggest that decreased hamstring strength significantly increases anterior cruciate ligament loading during anticipated sidestep cutting. Additionally, these results support the premise that preseason screening programs should monitor hamstring strength to identify female athletes with potential deficits and increased injury risk.     

Peak knee adduction moment during gait in anterior cruciate ligament reconstructed females

Background

Recent work has shown that anterior cruciate ligament reconstructed patients exhibit an increased peak knee adduction moment during walking gait compared to healthy controls. An increased peak knee adduction moment has been suggested to be a potential mechanism of degeneration for knee osteoarthritis. The few studies in this area have not considered an exclusively female anterior cruciate ligament reconstructed group. This study tested the hypothesis that female anterior cruciate ligament-reconstructed patients would have higher peak knee adduction moments than controls.

Methods

Peak knee adduction moment during walking was compared between a group of anterior cruciate ligament reconstructed females and a group of female activity matched controls over ten 15 m walking trials in a laboratory at a self-selected pace.

Findings

Peak knee adduction moment was lower for the anterior cruciate ligament reconstructed group (N = 17, M = 0.31 Nm/kg·m, SD = 0.08) than for the control group (N = 17, M = 0.41 Nm/kg·m, SD = 0.12; t(32) = 2.483, p = 0.010, one-tailed, eta squared effect size = 0.16).

Interpretation

A group of female anterior cruciate ligament reconstructed subjects did not exhibit a gait characteristic which has been suggested to be associated with knee osteoarthritis development and has been shown to be present in male and mixed sex anterior cruciate ligament reconstructed populations previously.