Recruitment of knee joint ligaments

On the basis of earlier reported data on the in vitro kinematics of passive knee-joint motions of four knee specimens, the length changes of ligament fiber bundles were determined by using the points of insertion on the tibia and femur. The kinematic data and the insertions of the ligaments were obtained by using Roentgenstereophotogrammetry. Different fiber bundles of the anterior and posterior cruciate ligaments and the medial and lateral collateral ligaments were identified. On the basis of an assumption for the maximal strain of each ligament fiber bundle during the experiments, the minimal recruitment length and the probability of recruitment were defined and determined. The motions covered the range from extension to 95 degrees flexion and the loading conditions included internal or external moments of 3 Nm and anterior or posterior forces of 30 N. The ligament length and recruitment patterns were found to be consistent for some ligament bundles and less consistent for other ligament bundles. The most posterior bundle of each ligament was recruited in extension and the lower flexion angles, whereas the anterior bundle was recruited for the higher flexion angles. External rotation generally recruited the collateral ligaments, while internal rotation recruited the cruciate ligaments. However, the anterior bundle of the posterior cruciate ligament was recruited with external rotation at the higher flexion angles. At the lower flexion angles, the anterior cruciate and the lateral collateral ligaments were recruited with an anterior force. The recruitment of the posterior cruciate ligament with a posterior force showed that neither its most anterior nor its most posterior bundle was recruited at the lower flexion angles. Hence, the posterior restraint must have been provided by the intermediate fiber bundles, which were not considered in the experiment. At the higher flexion angles, the anterior bundles of the anterior cruciate ligament and the posterior cruciate ligament were found to be recruited with anterior and posterior forces, respectively. The minimal recruitment length and the recruitment probability of ligament fiber bundles are useful parameters for the evaluation of ligament length changes in those experiments where no other method can be used to determine the zero strain lengths, ligament strains and tensions.     

Intrinsic innervation of the rat knee joint articular capsule and ligaments

In spite of the practical importance of having a detailed knowledge of knee joint innervation to understand the pathophysiologic aspects, little information is now available concerning the density and pattern of the nerve fibres which are distributed to it. The present study has been designed to investigate the density and distribution of nerve fibres and receptor corpuscles in the knee joint articular capsule, cruciate and collateral ligaments in the rat, using the acetylcholinesterase (AChE) histochemical in toto staining technique. The investigation was performed on male Wistar rats of 3 months of age, some of which had been treated with capsaicin to deplete their afferent 'C' fibres of their content of neuropeptides. AChE-positive nerve fibres and different types of receptor corpuscle endings were found within articular capsule and ligaments. The highest density of AChE-positive nerve fibres was noticeable in the fibular collateral ligament followed by the tibial collateral ligament, the posterior cruciate ligament, the anterior cruciate ligament and the articular capsule. In the articular capsule the number of type I endings was higher than in the ligaments. The opposite is true for the other type of receptor corpuscles found as well as for nerve endings. Capsaicin treatment significantly reduced the density of AChE-positive nerve fibres in knee joint ligaments but did not affect nerve fibres in the articular capsule. Moreover, it caused the disappearance of some kind of receptor corpuscles within the collateral and cruciate ligaments. The above data collectively suggest that the AChE in toto staining technique may represent a good method for investigating joint innervation and that a significant percentage of nerve fibres supplying knee joint ligaments is represented by C fibre afferents.     

Three-dimensional knee model: constrained by isometric ligament bundles and experimentally obtained tibio-femoral contacts

The purpose of this study is to investigate the effect of anterior portion of anterior cruciate ligament, posterior cruciate ligament, anterior and deep portions of medial collateral ligament and the tibio-femoral articular contacts on passive knee motion. A well-accepted reference model for a normal tibio-femoral joint is reconstructed from the literature. The proposed three-dimensional dynamic tibio-femoral model includes the isometric fascicles, ligament bundles and irregularly shaped medial-lateral contact surfaces. With the approach we aim to analyze bone shape and ligament related abnormalities of knee kinematics. The rotations, translations and the contact forces during passive knee flexion were compared against a reference model and the results were found in close accordance. This study demonstrated that isometric ligament bundles play an important role in understanding the femur shape from contact points on tibia. Femoral condyles are not necessarily spherical. The surgical treatments should consider both ligament bundle lengths and contact surface geometries to achieve a problem free knee kinematics after a knee surgery.     

双侧自体腘绳肌腱一期重建前后交叉韧带损伤的临床疗效

目的：探讨关节镜辅助下使用双侧自体腘绳肌腱一期修复膝关节前后交叉韧带损伤的方法和临床疗效。方法：内窥镜微创双侧自体腘绳肌腱修复膝关节内韧带,术后用IKDC分级、影像学IKDC分级、Lysholm功能评分和KT2000TM测量进行关节机能打分。结果：11例患者获得3—5年随访,平均随访3．8年。术前Lysholm功能评分平均（46．8±5．7）分,终末随访时平均（81．3±10．5）分,差异有显著性（P〈0．05）。术后关节稳定性测量,在20磅时、30磅和最大拉力时健膝和患膝分别是：6．1±0．3和6．8±0．8;6．3±0．5和7．7±1。3;7．5±0．6和9．6±2．4,统计学上差异无显著性（P〉0．05）。主观IKDC分级：A级4例,B级6例,C级1例;影像学IKDC分级：A级8例,B级2例,C级1例。结论：关节镜辅助下使用双侧自体腘绳肌腱一期修复膝关节前后交叉韧带损伤是重建膝关节稳定性的良好有效方法。     

A dynamic multibody model of the physiological knee to predict internal loads during movement in gravitational field

Obtaining tibio-femoral (TF) contact forces, ligament deformations and loads during daily life motor tasks would be useful to better understand the aetiopathogenesis of knee joint diseases or the effects of ligament reconstruction and knee arthroplasty. However, methods to obtain this information are either too simplified or too computationally demanding to be used for clinical application. A multibody dynamic model of the lower limb reproducing knee joint contact surfaces and ligaments was developed on the basis of magnetic resonance imaging. Several clinically relevant conditions were simulated, including resistance to hyperextension, varus–valgus stability, anterior–posterior drawer, loaded squat movement. Quadriceps force, ligament deformations and loads, and TF contact forces were computed. During anterior drawer test the anterior cruciate ligament (ACL) was maximally loaded when the knee was extended (392 N) while the posterior cruciate ligament (PCL) was much more stressed during posterior drawer when the knee was flexed (319 N). The simulated loaded squat revealed that the anterior fibres of ACL become inactive after 60° of flexion in conjunction with PCL anterior bundle activation, while most components of the collateral ligaments exhibit limited length changes. Maximum quadriceps and TF forces achieved 3.2 and 4.2 body weight, respectively. The possibility to easily manage model parameters and the low computational cost of each simulation represent key points of the present project. The obtained results are consistent with in vivo measurements, suggesting that the model can be used to simulate complex and clinically relevant exercises.     

A spatial mechanism with higher pairs for modelling the human knee joint

By generalizing a previous model proposed in the literature, a new spatial kinematic model of the knee joint passive motion is presented. The model is based on an equivalent spatial parallel mechanism which relies upon the assumption that fibers within the anterior cruciate ligament (ACL), the medial collateral ligament (MCL) and the posterior cruciate ligament (PCL) can be considered as isometric during the knee flexion in passive motion (virtually unloaded motion). The articular surfaces of femoral and tibial condyles are modelled as 3-D surfaces of general shapes. In particular, the paper presents the closure equations of the new mechanism both for surfaces represented by means of scalar equations that have the Cartesian coordinates of the points of the surface as variables and for surfaces represented in parametric form. An example of simulation is presented in the case both femoral condyles are modelled as ellipsoidal surfaces and tibial condyles as spherical surfaces. The results of the simulation are compared to those of the previous models and to measurements. The comparison confirms the expectation that a better approximation of the tibiofemoral condyle surfaces leads to a more accurate model of the knee passive motion.     

Balance index score as a predictive factor for lower sports results or anterior cruciate ligament knee injuries in Croatian female athletes--preliminary study

Female athletes participating in high-risk sports suffer anterior cruciate ligament (ACL) knee injury at a 4- to 6-fold greater rate than do male athletes. ACL injuries result either from contact mechanisms or from certain unexplained non-contact mechanisms occurring during daily professional sports activities. The occurrence of non-contact injuries points to the existence of certain factors intrinsic to the knee that can lead to ACL rupture. When knee joint movement overcomes the static and the dynamic constraint systems, non-contact ACL injury may occur. Certain recent results suggest that balance and neuromuscular control play a central role in knee joint stability, protection and prevention of ACL injuries. The purpose of this study is to evaluate balance neuromuscular skills in healthy Croatian female athletes by measuring their balance index score, as well as to estimate a possible correlation between their balance index score and balance effectiveness. This study is conducted in an effort to reduce the risk of future injuries and thus prevent female athletes from withdrawing from sports prematurely. We analysed fifty-two female athletes in the high-risk sports of handball and volleyball, measuring for their static and dynamic balance index scores, using the Sport KAT 2000 testing system. This method may be used to monitor balance and coordination systems and may help to develop simpler measurements of neuromuscular control, which can be used to estimate risk predictors in athletes who withdraw from sports due to lower sports results or ruptured anterior cruciate ligament and to direct female athletes to more effective, targeted preventive interventions. The tested Croatian female athletes with lower sports results and ACL knee injury incurred after the testing were found to have a higher balance index score compared to healthy athletes. We therefore suggest that a higher balance index score can be used as an effective risk predictor for lower sports results and lesser sports motivation, anterior cruciate ligament injury and the ultimate decision to withdraw from active participation in sports. If the balance testing results prove to be effective in predicting the occurrence of ligament injuries during future sports activities, we suggest that prophylactic training programs be introduced during athlete training, since the prevention of an initial injury will be more effective than prevention of injury recurrence.     

Prediction of total knee motion using a three-dimensional computer-graphics model

Twenty-three knees were sectioned, digitized, and standardized to determine the 'average' three-dimensional bony geometry and ligamentous attachments. Data on normal knee motion were obtained from a cadaveric study. An algorithm was written to simulate three-dimensional patella motion. Verification of the knee model was achieved by determining femoro-tibial and patello-femoral contact locations, as well as ligament length patterns, and comparing the results with published data. The criterion for maximum predicted knee motion with a prosthesis in place was the length of the posterior cruciate ligament. Three total knee replacement surfaces were mathematically generated: flat, laxity and conforming. A greater flexion angle was obtained with a flat tibial surface than for the laxity or conforming. Posterior tibial component displacement increased the range of motion, but only slightly. For all tibial surfaces, increased range of motion was achieved with a 10 degrees posterior tilt of the tibial tray. Anterior femoral component displacement increased motion due to reduction in posterior cruciate tension during flexion. The results are applicable to the design and surgical technique of total knee replacement.     

Effect of joint laxity on polyethylene wear in total knee replacement

Experimental simulator studies are frequently performed to evaluate wear behavior in total knee replacement. It is vital that the simulation conditions match the physiological situation as closely as possible. To date, few experimental wear studies have examined the effects of joint laxity on wear and joint kinematics and the absence of the anterior cruciate ligament has not been sufficiently taken into account in simulator wear studies.The aim of this study was to investigate different ligament and soft tissue models with respect to wear and kinematics.A virtual soft tissue control system was used to simulate different motion restraints in a force-controlled knee wear simulator.The application of more realistic and sophisticated ligament models that considered the absence of anterior cruciate ligament lead to a significant increase in polyethylene wear (p=0.02) and joint kinematics (p<0.01). We recommend the use of more complex ligament models to appropriately simulate the function of the human knee joint and to evaluate the wear behavior of total knee replacements. A feasible simulation model is presented.     

Effects of knee flexion on the structural properties of the rabbit femur-anterior cruciate ligament-tibia complex (FATC)

Many studies have been conducted to determine the biomechanical properties of the anterior cruciate ligament (ACL). The method of holding the femur-ACL-tibia complex (FATC) test specimen, the strain rate applied, the angle of knee flexion and the direction of the applied loads have an important effect on the outcome. It is felt that the tensile properties and strength of the ligament should be measured by applying the tensile force along the axis of the ligament. A versatile clamp was designed to accomplish this purpose. Fifty-seven rabbit knee specimens were tested at angles of flexion of 0 degrees, 30 degrees or 90 degrees. In addition, a comparative study of 25 pairs of rabbit legs were performed, whereby loading was either along the ligament or along the tibial axis. Cyclic hysteresis, ultimate load, energy absorbed, and stiffness were determined. The ultimate load values for the FATC decreased with increased knee flexion for those loaded along the tibial axis, while no such change was detected for FATC tested along the ligament axis. Other structural properties measured followed similar trends. It is concluded that the structural properties of the rabbit FATC change minimally with knee flexion (from 0 to 90 degrees) when loaded along the ligament axis, but decrease significantly with knee flexion when loaded along the axis of the tibia. Therefore, the data obtained in this field of study can be compared only if the direction of loading with respect to the ACL is similar.     

Description and error evaluation of an in vitro knee joint testing system

An experimental system for the analysis of knee joint biomechanics is presented. The system provides for the simultaneous recording of ligament forces using buckle transducers and three-dimensional joint motion using an instrumented spatial linkage, as in vitro specimens are subjected to a variety of external loads by a pneumatic loading apparatus with associated force transducers. The system components are described, and results of an evaluation of system errors and accuracy are presented. The experimental setup has been successfully used in the analysis of normal knee ligament mechanics, as well as surgical reconstructions of the anterior cruciate ligament. The system can also be adapted to test other human or animal in vitro joints.     

Using force sensing insoles to predict kinetic knee symmetry during a stop jump

Knee kinetic asymmetries are present during jump-landings in athletes returning to sport following anterior cruciate ligament (ACL) reconstruction, and are associated with an increased risk for sustaining a second ACL injury. The loadsol® is a wireless load sensing insole that can be used in non-laboratory settings. The purpose of this study was to determine if the loadsol® could be used to predict knee extension moment and power symmetry during a bilateral stop jump task in healthy recreational athletes. Forty-two uninjured recreational athletes completed seven bilateral stop jumps. During each landing, the loadsol® (100 Hz) measured plantar load while 3D ground reaction forces (1920 Hz) and lower extremity kinematics (240 Hz) were collected simultaneously. Peak impact force, loading rate, and impulse were quantified using the loadsol® and peak knee extension moment, average knee extension moment, and total knee work was quantified using the laboratory instrumentation. Limb symmetry indices were quantified for each outcome measure. Multivariate backwards regressions were used to determine if loadsol® symmetry could predict knee kinetic symmetry. Intraclass correlation coefficients (ICCs) and Bland-Altman plots were used to determine the agreement and error between predicted and actual knee kinetic symmetry. Loadsol® impulse and peak impact force symmetry significantly predicted kinetic knee symmetry and explained 42–61% of its variance. There was good agreement (ICCs = 0.742–0.862) between predicted and actual knee kinetic symmetry, and the error in the predicted outcomes range from ±18 to ±43. These results support using the loadsol® to screen for kinetic symmetries during landing in athletes following ACL reconstruction.     

Increasing quadriceps loads affect the lengths of the ligaments and the kinematics of the knee.

The relationships between the lengths of the ligaments and kinematics of the knee and quadriceps load, for low to physiologic levels of quadriceps loads, have not previously been studied. We investigated the effects of increasing levels of quadriceps force, necessary to balance increasing levels of externally applied flexion moments, on the kinematics of the tibiofemoral joint and on the separation distances between insertions of selected fibers of the major ligaments of the knee in twelve cadavera. Static measurements were made using a six-degree-of-freedom digitizer for flexion angles ranging from 0 to 120 deg in 15 deg increments. Quadriceps generated extension of the knee was performed by applying loads to the quadriceps tendon to equilibrate each of four magnitudes of external flexion moments equivalent to 8.33, 16.67, 25.00, and 33.33 percent of values previously reported for maximum isometric extension moments. The magnitude of quadriceps force increased linearly (p < 0.0001) as external flexion moment increased throughout the entire range of flexion. Anterior translation, internal rotation, and abduction of the tibia increased linearly (p < 0.0001, p < 0.001, p < 0.001) as external flexion moment and, hence, quadriceps load increased. For the fibers studied, the anterior cruciate ligament (p < 0.0076), posterior cruciate ligament (p < 0.0001), and medial collateral ligament (p < 0.0383) lengthened linearly while the lateral collateral ligament (p < 0.0124) shortened linearly as quadriceps load increased. Based on these results for low to physiologic levels of quadriceps loads, it is reasonable to assume that the ligament lengths or knee kinematics expected with higher quadriceps loads can be extrapolated.     

Comparison of material properties in fascicle-bone units from human patellar tendon and knee ligaments

The fascicle material properties in bone-fascicle-bone units were determined for the anterior and posterior cruciate ligaments (ACL, PCL), the lateral collateral ligament (LCL) and the patellar tendon (PT) from three young human donor knees. Groups of fascicles from each tissue were isolated with intact bone ends and failed at a high strain rate in a saline bath at 37 degrees C. In each knee tested the load related material properties (linear modulus, maximum stress and energy density to maximum stress) for the patellar tendon were significantly larger than corresponding values for the cruciate and collateral ligaments. Bundles from different ligaments in the same knee were similar to each other in their mechanical behavior. In addition, no significant differences were present in the maximum strains recorded for any of the four tissue types examined. The results presented have implications in studies of ligament injury. They are also important in the design and use of synthetic and biological ligament replacements and in tissue and whole knee modeling.     

Pure passive hyperextension of the human cadaver knee generates simultaneous bicruciate ligament rupture

Knee hyperextension has been described as a mechanism of isolated anterior cruciate ligament (ACL) tears, but clinical and experimental studies have produced contradictory results for the ligament injuries and the injury sequence caused by the hyperextension loading mechanism. The hypothesis of this study was that bicruciate ligament injuries would occur as a result of knee hyperextension by producing high tibio-femoral (TF) compressive forces that would cause anterior translation of the tibia to rupture the ACL, while joint extension would simultaneously induce rupture of the posterior cruciate ligament (PCL). Six human knees were loaded in hyperextension until gross injury, while bending moments and motions were recorded. Pressure sensitive film documented the magnitude and location of TF compressive forces. The peak bending moment at failure was 108?N?m±46?N?m at a total extension angle of 33.6?deg±11?deg. All joints failed by simultaneous ACL and PCL damages at the time of a sudden drop in the bending moment. High compressive forces were measured in the anterior compartments of the knee and likely produced the anterior tibial subluxation, which contributed to excessive tension in the ACL. The injury to the PCL at the same time may have been due to excessive extension of the joint. These data, and the comparisons with previous experimental studies, may help explain the mechanisms of knee ligament injury during hyperextension. Knowledge of forces and constraints that occur clinically could then help diagnose primary and secondary joint injuries following hyperextension of the human knee.     

Effect of changes in cruciate ligaments pretensions on knee joint laxity and ligament forces

The knee joint cruciate ligaments are reconstructed with the rationale to avoid joint instability, recurrent injury, damage to soft tissues and osteoarthritis. Wide range of procedures with different stiffness, pretension, orientation and insertion locations have been proposed with the primary goal to restore the joint laxity. Apart from the general lack of success in preservation of force in the reconstructed ligament itself, the concern, not yet addressed, arises as to the effect of such perturbation on the other intact cruciate ligament. The interaction between cruciate ligament forces is hypothesized in this work. Using a 3-D nonlinear finite element model of the tibiofemoral joint, we examined this hypothesis by quantifying the extent of coupling between cruciate ligaments while varying the prestrain in each ligament under flexion with and without anterior-posterior (A-P) loads. A remarkable coupling was predicted between cruciate ligament forces in flexion thus confirming the hypothesis; forces in both cruciate ligaments increased as initial strain or pretension in one of them increased whereas they both diminished as one of them became slack. Moreover, changes in laxity and in ligament forces as a cruciate ligament prestrained or pretensioned varied with flexion angle and external loads. These findings have important consequences in joint functional biomechanics following a ligament injury or replacement surgery and in selection of laxity matched or ligament force matched pretensioning protocols.     

Anatomy of the cruciate ligaments and their function in extension and flexion of the human knee joint

The areas of the femoral origin of the cruciate ligaments have approximately the shape of sectors of ellipses, the one for the anterior ligament on the lateral condyle posteroproximally and the one for the posterior ligament on the medial condyle distally. By means of a new technique of dissection, combined with the use of X-rays, the change in distance between the origin and insertion and so the change of tension of single bundles of the ligaments could be analyzed. Only a rather thin bundle in each cruciate ligament is in constant tension: "guiding bundles." The maximal diminution of distance between the origin and insertion for some bundles is 65%. In the anterior cruciate ligament the majority of fibres are taut in extreme extension: "limiting bundles." The same is true in the posterior cruciate ligament in extreme flexion. There are also some fibres, especially in the posterior cruciate ligament, that are taut only in an intermediate position. The geometric analysis of the function of different groups of fibers was performed by a modification of Menschik's concept of a four-bar link.     

A three-dimensional study of the kinematics of the human knee

This paper represents a three-dimensional study of the human knee-joint and studies kinematic effects of the cruciate ligaments. Two methods were used for our studies, one method was preferred. This method used a time lapse photograph and strobe light to give us a plot of reference points to carry out our analysis using the method of Rouleaux applied to three dimensions. Five cadaver joints were used, each of which was used for three series of experiments, including the joint with capsule intact, with one of the ligaments cut and with the remaining ligament cut. Both lateral and medial studies were conducted to provide data for a three-dimensional study.

It was found that the cruciate ligaments had little effect on the kinematics of the knee, and that the knee motion remained unchanged after cutting one or both of the cruciate ligaments. It was concluded that the motion of the knee was due to the geometry of the bones and perhaps the collateral ligaments, and that the joint could be replaced with a prosthesis having a three dimensional axis of rotation with a fixed center.     

The influence of ligament modelling strategies on the predictive capability of finite element models of the human knee joint

In finite element (FE) models knee ligaments can represented either by a group of one-dimensional springs, or by three-dimensional continuum elements based on segmentations. Continuum models closer approximate the anatomy, and facilitate ligament wrapping, while spring models are computationally less expensive. The mechanical properties of ligaments can be based on literature, or adjusted specifically for the subject. In the current study we investigated the effect of ligament modelling strategy on the predictive capability of FE models of the human knee joint. The effect of literature-based versus specimen-specific optimized material parameters was evaluated. Experiments were performed on three human cadaver knees, which were modelled in FE models with ligaments represented either using springs, or using continuum representations. In spring representation collateral ligaments were each modelled with three and cruciate ligaments with two single-element bundles. Stiffness parameters and pre-strains were optimized based on laxity tests for both approaches. Validation experiments were conducted to evaluate the outcomes of the FE models.Models (both spring and continuum) with subject-specific properties improved the predicted kinematics and contact outcome parameters. Models incorporating literature-based parameters, and particularly the spring models (with the representations implemented in this study), led to relatively high errors in kinematics and contact pressures. Using a continuum modelling approach resulted in more accurate contact outcome variables than the spring representation with two (cruciate ligaments) and three (collateral ligaments) single-element-bundle representations. However, when the prediction of joint kinematics is of main interest, spring ligament models provide a faster option with acceptable outcome.