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.     

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.     

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.     

Clinically-relevant measures associated with altered contact forces in patients with anterior cruciate ligament deficiency

Background

Knee joint contact forces are altered after anterior cruciate ligament injury during walking and may be related to clinically-relevant measures of impairments or self-reported function. The purpose of this study was to investigate the association of several clinically-relevant measures with altered knee contact forces in patients with anterior cruciate ligament injury.

Methods

Data for this study represent a cross-sectional observational analysis of thirty-seven (23 M, 14 F) patients with complete unilateral anterior cruciate ligament injury. Gait analysis with electromyography was used to obtain estimates of tibiofemoral joint contact force using an electromyography-driven musculoskeletal model. Multivariable linear regression was used to identify measures associated with tibiofemoral joint contact force.

Findings

Involved knee extensor muscle strength and patient-reported knee function on the Global Rating Scale of perceived function were significantly associated with peak tibiofemoral contact force for the involved limb. Patients who were stronger and who perceived higher knee function walked with greater contact forces on their involved knees. After controlling for walking speed, involved extensor strength explained 8.9% of the variance in involved peak tibiofemoral contact force and score on the Global Rating Scale explained an additional 9.4% of the variance.

Interpretation

Improvements in involved quadriceps strength and overall function as measured by patient self-report may be important for increasing involved limb contact forces, thereby restoring loading symmetry in these patients who demonstrate decreased involved limb loading after injury. These results highlight the potential value of studying the recovery of strength, self-reported function and joint loading symmetry in patients with anterior cruciate ligament injury.     

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.     

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.     

Tibial rotation during pivoting in anterior cruciate ligament reconstructed knees using a single bundle technique

Background

Anterior cruciate ligament reconstruction does not necessarily restore normal knee movement. Increased tibial rotation has previously been noted during pivoting activities and may be due to the orientation of the anterior cruciate ligament graft associated with traditional single bundle reconstruction techniques. Recent research has shown that it is possible to limit rotation during level walking using a single bundle anterior cruciate ligament reconstruction. This study evaluated rotational knee kinematics during a pivot task in a group of patients who had undergone anterior cruciate ligament reconstruction using a single bundle technique and compared the findings to a normal control group.

Methods

In 27 anterior cruciate ligament reconstruction and 25 control participants, internal–external rotation was measured during a descend stairs and pivot task in a gait laboratory.

Findings

Results showed that the anterior cruciate ligament reconstruction patients had less internal tibial rotation (for both range of rotation and maximum rotation) than the control participants (effect size = 0.7).

Interpretation

These results suggest that it is possible to limit rotation after anterior cruciate ligament reconstruction using a single bundle technique, even during a pivoting movement that places a high rotational load at the knee joint. The positioning of the femoral tunnel in a more anatomical position may be responsible for the reduced tibial rotation.     

Anticipatory effects on anterior cruciate ligament loading during sidestep cutting

Background

A key to understanding potential anterior cruciate ligament injury mechanisms is to determine joint loading characteristics associated with an injury-causing event. However, direct measurement of anterior cruciate ligament loading during athletic tasks is invasive. Thus, previous research has been unable to study the association between neuromuscular variables and anterior cruciate ligament loading. Therefore, the purpose of this study was to determine the influence of movement anticipation on anterior cruciate ligament loading using a musculoskeletal modeling approach.

Methods

Twenty healthy recreationally active females were recruited to perform anticipated and unanticipated sidestep cutting. Three-dimensional kinematics and kinetics of the right leg were calculated. Muscle, joint and anterior cruciate ligament forces were then estimated using a musculoskeletal model. Dependent t-tests were conducted to investigate differences between the two cutting conditions.

Findings

ACL loading significantly increased during unanticipated sidestep cutting (p < 0.05). This increase was primarily due to a significant increase in the sagittal plane ACL loading, which contributed 62% of the total loading. Frontal plane ACL loading contributed 26% and transverse plane ACL loading contributed 12%.

Interpretation

These results suggest that anterior cruciate ligament loading resulted from a multifaceted interaction of the sagittal plane shear forces (i.e., quadriceps, hamstrings, and tibiofemoral), as well as the frontal and transverse plane knee moments. Additionally, the results of this study confirm the hypothesis in the current literature that unanticipated movements such as sidestep cutting increase anterior cruciate ligament loading.     

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.     

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.     

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.     

The effects of ACL injury on knee proprioception: a meta-analysis

Background

It is suggested the anterior cruciate ligament (ACL) plays a significant role in knee proprioception, however, the effect of ACL injury on knee proprioception is unclear. Studies utilising the two most common measurement techniques, joint position sense and threshold to detect passive motion, have provided evidence both for and against a proprioceptive deficient following ACL injury.

Objective

The objective of the study was to undertake a meta-analysis investigating the effects of ACL injury, treated conservatively or by reconstruction, on proprioception of the knee, measured using joint position sense and/or threshold to detect passive movement techniques.

Data sources

Seven databases were searched from their inception to September 2013 using the subject headings ‘anterior cruciate ligament, proprioception, postural sway, joint position sense, balance, equilibrium or posture’ to identify relevant studies.

Eligibility criteria

PRISMA guidelines were followed as much as possible. Studies that investigated the effect of ACL injury on either knee joint kinaesthesia or position sense were included in this review.

Data extraction and synthesis

Two reviewers independently extracted data using a standardised assessment form. Comparisons were made using a fixed effect model with an inverse variance method using Review Manager Software (V5.1).

Results

Patients with ACL injury have poorer proprioception than people without such injuries (SMD = 0.35°; P = 0.001 and SMD = 0.38°; P = 0.03) when measured using joint position sense and threshold to detect passive motion techniques respectively. Patients had poorer proprioception in the injured than uninjured leg (SMD = 0.52°; P < 0.001) and the proprioception of people whose ACL was repaired was better than those whose ligament was left unrepaired (SMD = −0.62°; P < 0.001).

Limitations

Heterogeneity of measurement techniques and lack of psychometric details.

Conclusion

ACL injuries may cause knee proprioception deficits compared to uninjured knees and control groups. Although differences were statistically significant, the clinical significance of findings can be questioned. Clinical practitioners using joint position sense or threshold to detect passive motion techniques need to consider the reliability and validity of data provided.     

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.     

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.     

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.     

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.     

Sagittal plane knee joint moments following anterior cruciate ligament injury and reconstruction: A systematic review

Background

Gait adaptations in persons with anterior cruciate ligament (ACL) injuries have been debated. Many studies examine high speed, 3-dimensional video gait analysis to compare knee joint torques during simulated activities of daily living.

Methods

We performed a systematic review of the literature for published clinical papers that reported sagittal plane knee joint kinetics in ACL deficient or reconstructed individuals. We calculated weighted effect sizes (Cohen’s d) to evaluate the magnitude of differences between the injured limb and the contralateral limb and healthy, uninjured limbs in control subjects.

Findings

Ten published papers reported kinetic data in ACL deficient subjects while walking for comparisons to the contralateral side (weighted average d = −0.83, range: −3.21, 1.07), and to healthy control knees (weighted average d = −1.0, range: −3.36, 0.17); four papers reported data during jogging compared to the contralateral side (weighted average d = −0.94, range: −4.15, 0.17), and to controls (weighted average d = −1.42, range: −3.83,−0.2). Four papers reported data for ACL-reconstructed patients compared to healthy controls during walking (weighted average d = −0.94, range: −0.4, −1.77) and jogging (weighted average d = −1.18).

Interpretation

Effect sizes comparing knee joint moments in injured vs. healthy control subjects appear to be slightly higher while jogging than walking, and higher in ACL-deficient patients compared to reconstructions. However, magnitudes are all large. Few studies report stair climbing. Consequently, it is difficult to make inferences with confidence during these tasks.     

Osteochondral microdamage from valgus bending of the human knee

Background

Valgus bending of the knee is promoted as an anterior cruciate ligament injury mechanism and is associated with a characteristic “footprint” of bone bruising. The hypothesis of this study was that during ligamentous failure caused by valgus bending of the knee, high tibiofemoral contact pressures induce acute osteochondral microdamage.

Methods

Four knee pairs were loaded in valgus bending until gross injury with or without a tibiofemoral compression pre-load. The peak valgus moment and resultant motions of the knee joint were recorded. Pressure sensitive film documented the magnitude and location of tibiofemoral contact. Cartilage fissures were documented on the tibial plateau, and microcracks in subchondral bone were documented from micro-computed tomography scans.

Findings

Injuries were to the anterior cruciate ligament in three knees and the medial collateral ligament in seven knees. The mean (standard deviation) peak bending moment at failure was 107 (64) N m. Valgus bending produced regions of contact on the lateral tibial plateau with average maximum pressures of approximately 30 (8) MPa. Cartilage fissures and subchondral bone microcracks were observed in these regions of high contact pressure.

Interpretation

Combined valgus bending and tibiofemoral compression produce slightly higher contact pressures, but do not alter the gross injury pattern from isolated valgus bending experiments. Athletes who sustain a severe valgus knee bending moment, may be at risk of acute osteochondral damage especially if the loading mechanism occurs with a significant tibiofemoral compression component.     

Analysis of partial meniscectomy and ACL reconstruction in knee joint biomechanics under a combined loading

Background

Despite partial meniscectomies and ligament reconstructions as treatments of choice for meniscal and ligament injuries, respectively, the knee joint osteoarthritis persists.

Methods

A detailed nonlinear finite element model of the knee joint was developed to evaluate biomechanics of the tibiofemoral joint under 200 N drawer load with and without 1500 N compression preload. The model incorporated composite structure of cartilage and meniscus. The effects on joint response and articular contact pressure of unilateral partial meniscectomy, of changes in prestrain or material properties of the anterior cruciate ligament and of their combination were investigated.

Findings

Compressive preload further increases anterior cruciate ligament strains/forces in drawer loading. Partial meniscectomy and perturbations in anterior cruciate ligament prestrain/material properties, alone or combined, substantially alter the load transfer via covered and uncovered areas of cartilage as well as contact pressure distribution on cartilage. Partial meniscectomy especially when combined with a slacker anterior cruciate ligament diminish the load via affected meniscus generating unloaded regions on the cartilage.

Interpretation

Partial meniscectomy concurrent with a slack anterior cruciate ligament substantially alter cartilage contact pressures. These alterations further intensify in the event of greater external forces, larger meniscal resections and total anterior cruciate ligament rupture, thus suggesting a higher risk of joint degeneration.