Search Results (17)

This study aims to quantify the contributions of external, muscle, and ligament forces to the tibiofemoral contact loads during gait. Additionally, the relative contributions in patients with knee osteoarthritis (KOA) and healthy individuals were also compared. For this aim, twenty medial Kellgren–Lawrence (KL) 3–4 KOA patients and twenty healthy controls were recruited to perform the gait data collection experiment using a motion capture and force plate system. The relative contributions were calculated based on an improved musculoskeletal model with knee ligaments. The results showed that the contribution of muscle forces to the total compartment contact loads was greater than that of external forces for both the healthy individuals and the KOA patients. The medial compartment contact loads were contributed predominantly by external forces, and the lateral compartment contact loads were contributed negatively by external forces for both the healthy individuals and the KOA patients. For the healthy individuals, the total/lateral compartment contact loads were predominantly contributed by muscle forces. The ligament forces provide a contribution similar to muscle forces to the medial compartment contact loads. For the KOA patients, the total/lateral compartment contact loads were contributed predominantly by ligament forces. The ligament forces provide a negative contribution to the medial compartment contact loads. In conclusion, the knee ligaments provided important contributions to the tibiofemoral contact loads. Significant differences were found in the relative contributions between the KOA patients and the healthy individuals. The results of this study have significant clinical implications for further improving the current biomechanical treatments of KOA. Full article

This study presents a comprehensive three-dimensional finite element (FE) model inspired by the biomechanics of the human knee, specifically the tibiofemoral joint during the gait cycle. Drawing from natural biological systems, the model integrates bio-inspired elements, including transversely isotropic materials, to replicate the anisotropic properties of ligaments and cartilage, along with anatomically realistic bone and meniscus structures. This dual-material approach ensures a physiologically accurate representation of knee mechanics under varying conditions. The model effectively captures key biomechanical parameters, including a maximum medial tibial cartilage contact pressure of 16.75 MPa at 25% of the stance phase and a maximum femoral cartilage pressure of 10.57 MPa at 75% of the stance phase. Furthermore, its strong correlation with in vivo and in vitro data highlights its potential for clinical applications in orthopedics, such as pre-surgical planning and post-operative assessments. By bridging the gap between biomechanics and bioinspired design, this research contributes significantly to the field of biomimetics and offers a robust simulation tool for enhancing joint protection strategies and optimizing implant designs. Full article

Background/Objectives: Total knee arthroplasty (TKA) is the gold-standard treatment for advanced knee arthritis, offering pain relief and improved joint function. However, tibial component malalignment, malrotation, and improper biomechanical loading remain critical factors contributing to implant failure, instability, and revision surgeries. This review systematically examines the impact of biomechanical loading on the tibial insert following primary TKA, with a focus on alignment, posterior tibial slope (PTS), and load distribution. Methods: A systematic literature search was conducted across the PubMed, Google Scholar, and Web of Science databases following the PRISMA guidelines. Studies investigating the effects of tibial component alignment, varus/valgus deviations, PTS, and load distribution on tibial inserts post-TKA were included. Seven studies meeting the inclusion criteria were analyzed and described narratively. Results: The reviewed studies highlighted that varus and valgus malalignment significantly alter tibiofemoral contact pressures and ligament strains, increasing the risk of aseptic loosening and implant failure. Excessive PTS was associated with posterior femoral translation, altered ligament tension, and increased contact stresses on polyethylene (PE) inserts. Kinematically aligned TKA demonstrated reduced tibial force imbalances and improved functional outcomes compared to mechanically aligned TKA. Computational and cadaveric studies revealed that even minor malalignments (e.g., 3° varus or valgus) can cause significant biomechanical changes. Conclusions: Biomechanical loading on tibial inserts after primary TKA is highly sensitive to the alignment and PTS. Optimal alignment and controlled biomechanical forces are essential. Kinematically aligned TKA has shown promising effects, preventing aseptic loosening and ensuring long-term implant survival. Further in vivo studies are needed to validate these findings and optimize surgical techniques. Full article

The objective of this study was to develop a musculoskeletal model incorporated with a subject-specific knee joint to predict the tibiofemoral contact force (TFCF) during daily motions. For this purpose, 18 healthy participants were recruited to perform the motion data acquisition using synchronized motion capture and force platform systems, and motion simulation based on an improved musculoskeletal model for five daily activities, including normal walking, stair ascent, stair descent, sit-to-stand, and stand-to-sit. The proposed musculoskeletal model included subject-specific models of bones, cartilages, and meniscus, detailed knee ligaments and muscles, deformable elastic contacts, and multiple degrees of freedom (DOFs) of the knee joint. The prediction accuracy was demonstrated by the good agreements of TFCF curves between the model predictions and in vivo measurements for the five activities (RMSE: 0.216~0.311 BW, R²: 0.928~0.992, and C_E: 0.048~0.141). Based on the validated model, the TFCF on total, medial, and lateral compartments (TFCF_Total, TFCF_Medial, and TFCF_Lateral) during the five daily activities were predicted. For TFCF_Total, the peak force for stair descent or sit-to-stand was the largest, followed by stair ascent or stand-to-sit, and finally normal walking. For TFCF_Medial, stair descent had the largest peak, followed by stair ascent. There were no significant differences between the peak TFCF_Medial values of normal walking, sit-to-stand, and stand-to-sit. For TFCF_Lateral, the peak of sit-to-stand was the largest, followed by stand-to-sit or stair descent, and finally normal walking or stair ascent. This study is valuable for further understanding the biomechanics of a healthy knee joint and providing theoretical guidance for the treatment of knee osteoarthritis (KOA). Full article

This research investigates the biomechanical effects of a novel ceramic implant for the treatment of canine cranial cruciate ligament rupture (CCLR) based on the tibial tuberosity advancement (TTA) method using finite element analysis (FEA). A 3D FEA of the tibiofemoral joint simulating the applied forces (44.5% of body weight) during the mid-stance phase (joint angle 135°) of the dog’s stride was performed. Three conditions were considered for each joint: the physiological condition, the pathological condition with CCLR and the restored condition after TTA. Eight cadavers were used to create fifteen paired knee joints. The results showed significant differences in the forces that could be measured in the patellar tendon (PT) and in the cranial displacement of the tibial tuberosity between the conditions. The PT forces increased in the pathological state and continued to increase in the restored state, while the cranial displacement of the tibial tuberosity increased in the pathological state and decreased again in the restored state. Correlation analyses revealed significant correlations between PT forces, body weight and cranial displacement. The FEA provides initial insights into the force distribution and functionality of the ceramic implant. However, further testing is required to validate reliability and evaluate the efficacy of the implant. Full article

Anterior–posterior (AP) stability is an important measure of knee performance after total knee arthroplasty (TKA). To improve the stabilizing effect of implants designed to compensate for the loss of the cruciate ligaments, it is important to understand the tibiofemoral contact situation within the native ligamentous situation of the knee and how it changes after cruciate ligament resection. This in vitro study introduces a new approach to accurately measure the tibiofemoral kinematics in a six-degrees-of-freedom joint motion simulator by tracking landmark-based coordinate systems and their corresponding bone geometries. The tibiofemoral contact situation was investigated by projecting the medial and lateral flexion facet centers onto the tibial plateau under AP shear forces across various flexion angles in thirteen knees. Tests were conducted pre- and post-cruciate ligament resection. Post-cruciate ligament resection, the femoral condyles shifted closer to or even exceeded the posterior border of the tibial plateau, but only slightly closer to the anterior border. This study presents a new methodology for measuring the tibiofemoral kinematics that can be applied to multiple loading profiles. It provides a basis for further investigations, including passive or active muscle forces, to enhance the design of total knee protheses and improve surgical outcomes. Full article

Purpose: The aim of this study was to evaluate the presence of residual instability in the knee after ACL reconstruction through the analysis of MRI findings. Methods: This study included patients who underwent isolated ACL reconstruction between December 2019 and December 2021, and had preoperative and postoperative MRI, clinical scores, and postoperative isokinetic measurements. The anterior tibial translation (ATT) distance, coronal lateral collateral ligament (LCL) sign, and femorotibial rotation (FTR) angle were compared preoperatively and postoperatively. The correlation between the changes in preoperative–postoperative measurements and postoperative measurements with clinical scores and isokinetic measurements was examined. The clinical outcomes were compared based on the presence of a postoperative coronal LCL sign. Inclusion criteria were set as follows: the time between the ACL rupture and surgery being 6 months, availability of preoperative and postoperative clinical scores, and objective determination of muscle strength using isokinetic dynamometer device measurements. Patients with a history of previous knee surgery, additional ligament injuries other than the ACL, evidence of osteoarthritis on direct radiographs, cartilage injuries lower limb deformities, and contralateral knee injuries were excluded from this study. Results: This study included 32 patients. After ACL reconstruction, there were no significant changes in the ATT distance (preoperatively: 6.5 ± 3.9 mm, postoperatively: 5.7 ± 3.2 mm) and FTR angle (preoperatively: 5.4° ± 2.9, postoperatively: 5.2° ± 3.5) compared to the preoperative measurements (p > 0.05). The clinical measurements were compared based on the presence of a postoperative coronal LCL sign (observed in 17 patients, not observed in 15 patients), and no significant differences were found for all parameters (p > 0.05). There were no observed correlations between postoperative FTR angle, postoperative ATT distance, FTR angle change, and ATT distance change values with postoperative clinical scores (p > 0.05). Significant correlations were observed between the high strength ratios generated at an angular velocity of 60° and a parameters FTR angle and ATT distance (p-values: 0.028, 0.019, and r-values: −0.389, −0.413, respectively). Conclusions: Despite undergoing ACL reconstruction, no significant changes were observed in the indirect MRI findings (ATT distance, coronal LCL sign, and FTR angle). These results suggest that postoperative residual tibiofemoral rotation and tibial anterior translation may persist; however, they do not seem to have a direct impact on clinical scores. Furthermore, the increase in tibial translation and rotation could potentially negatively affect the flexion torque compared to the extension torque in movements requiring high torque at low angular velocities. Full article

The understanding of the changes induced in the knee’s kinematics by a Posterior Cruciate Ligament (PCL) injury is still rather incomplete. This computational study aimed to analyze how the internal loads are redistributed among the remaining ligaments when the PCL is lesioned at different degrees and to understand if there is a possibility to compensate for a PCL lesion by changing the hamstring’s contraction in the second half of the swing phase. A musculoskeletal model of the knee joint was used for simulating a progressive PCL injury by gradually reducing the ligament stiffness. Then, in the model with a PCL residual stiffness at 15%, further dynamic simulations of walking were performed by progressively reducing the hamstring’s force. In each condition, the ligaments tension, contact force and knee kinematics were analyzed. In the simulated PCL-injured knee, the Medial Collateral Ligament (MCL) became the main passive stabilizer of the tibial posterior translation, with synergistic recruitment of the Lateral Collateral Ligament. This resulted in an enhancement of the tibial–femoral contact force with respect to the intact knee. The reduction in the hamstring’s force limited the tibial posterior sliding and, consequently, the tension of the ligaments compensating for PCL injury decreased, as did the tibiofemoral contact force. This study does not pretend to represent any specific population, since our musculoskeletal model represents a single subject. However, the implemented model could allow the non-invasive estimation of load redistribution in cases of PCL injury. Understanding the changes in the knee joint biomechanics could help clinicians to restore patients’ joint stability and prevent joint degeneration. Full article

Ultrasound-based ligament strain estimation shows promise in non-invasively assessing knee joint collateral ligament behavior and improving ligament balancing procedures. However, the impact of ultrasound-based strain estimation residual errors on in-silico arthroplasty predictions remains unexplored. We investigated the sensitivity of post-arthroplasty kinematic predictions to ultrasound-based strain estimation errors compared to clinical inaccuracies in implant positioning.Two cadaveric legs were submitted to active squatting, and specimen-specific rigid computer models were formulated. Mechanical properties of the ligament model were optimized to reproduce experimentally obtained tibiofemoral kinematics and loads with minimal error. Resulting remaining errors were comparable to the current state-of-the-art. Ultrasound-derived strain residual errors were then introduced by perturbing lateral collateral ligament (LCL) and medial collateral ligament (MCL) stiffness. Afterwards, the implant position was perturbed to match with the current clinical inaccuracies reported in the literature. Finally, the impact on simulated post-arthroplasty tibiofemoral kinematics was compared for both perturbation scenarios. Ultrasound-based errors minimally affected kinematic outcomes (mean differences < 0.73° in rotations, 0.1 mm in translations). Greatest differences occurred in external tibial rotations (−0.61° to 0.73° for MCL, −0.28° to 0.27° for LCL). Comparatively, changes in implant position had larger effects, with mean differences up to 1.95° in external tibial rotation and 0.7 mm in mediolateral translation. In conclusion, our study demonstrated that the ultrasound-based assessment of collateral ligament strains has the potential to enhance current computer-based pre-operative knee arthroplasty planning. Full article

Knee osteoarthritis is a musculoskeletal defect specific to the soft tissues in the knee joint and is a degenerative disease that affects millions of people. Although drug intake can slow down progression, total knee arthroplasty has been the gold standard for the treatment of this disease. This surgical procedure involves replacing the tibiofemoral joint with an implant. The most common implants used for this require the removal of either the anterior cruciate ligament (ACL) alone or both cruciate ligaments which alters the native knee joint mechanics. Bi-cruciate-retaining implants have been developed but not frequently used due to the complexity of the procedure and the occurrences of intraoperative failures such as ACL and tibial eminence rupture. In this study, a knee joint implant was modified to have a bone graft that should aid in ACL reconstruction. The mechanical behavior of the bone graft was studied through finite element analysis (FEA). The results show that the peak Christensen safety factor for cortical bone is 0.021 while the maximum shear stress of the cancellous bone is 3 MPa which signifies that the cancellous bone could fail when subjected to the ACL loads, depending on the graft shear strength which could vary depending on the graft source, while cortical bone could withstand the walking load. It would be necessary to optimize the bone graft geometry for stress distribution as well as to evaluate the effectiveness of bone healing prior to implementation. Full article

Background. Stair climbing is often performed by people in daily life and requires considerable energy and muscle effort. This task has been widely described in the literature, but the role of the knee joint ligaments has not been sufficiently investigated. This could be relevant for planning ligament reconstruction surgery, for providing suggestions to subjects with partial ligament injuries, and for identifying compensatory strategies for reducing ligament loads. Methods. A dynamic musculoskeletal model was used to analyse the relationship between ligament loads and muscle forces during stair climbing. Results. The most loaded ligaments were the posterior cruciate ligament and the deep fibres of the medial collateral ligament, particularly during the mid-swing phase, where the knee was maximally flexed and the hamstring muscles contracted. The anterior cruciate ligament was recruited during the stance phase to compensate for the anteriorly-directed force applied to the tibia by the vasti muscles; the collateral ligaments stabilized the knee joint during the swing phase. The tibiofemoral contact force, resulting from all external and internal forces applied to the knee, was in good agreement with data provided in the literature. Conclusions. This study represents a forward step in the knowledge of ligament loads during stair climbing, which could be useful for providing informed recommendations to subjects with ligament injuries. Full article

There is little known about kinetic changes in anterior cruciate ligament deficiency (ACLD) combined with meniscal tears during jogging. Therefore, 29 male patients with injured ACLs and 15 healthy male volunteers were recruited for this study to investigate kinetic abnormalities in male patients after ACL deficiency combined with a meniscal injury during jogging. Based on experimental data measured by an optical tracking system, a subject-specific musculoskeletal model was employed to estimate the tibiofemoral joint kinetics during jogging. Between-limb and interpatient differences were compared by the analysis of variance. The results showed that decreased knee joint forces and moments of both legs in ACLD patients were detected during the stance phase compared to the control group. Meanwhile, compared with ACLD knees, significantly fewer contact forces and flexion moments in ACLD combined with lateral and medial meniscal injury groups were found at the mid-stance, and ACLD with medial meniscal injury group showed a lower axial moment in the loading response (p < 0.05). In conclusion, ACLD knees exhibit reduced tibiofemoral joint forces and moments during jogging when compared with control knees. A combination of meniscus injuries in the ACLD-affected side exhibited abnormal kinetic alterations at the loading response and mid-stance phase. Full article

An improved understanding of the relationships between bone morphology and in vivo tibio-femoral kinematics potentially enhances functional outcomes in patients with knee disorders. The aim of this study was to quantify the influence of femoral and tibial bony morphology on tibio-femoral kinematics throughout complete gait cycles in healthy subjects. Twenty-six volunteers underwent clinical examination, radiographic assessment, and dynamic video-fluoroscopy during level walking, downhill walking, and stair descent. Femoral computer-tomography (CT) measurements included medial condylar (MC) and lateral condylar (LC) width, MC and LC flexion circle, and lateral femoral condyle index (LFCI). Tibial CT measurements included both medial (MTP) and lateral tibial plateau (LTP) slopes, depths, lengths, and widths. The influence of bony morphology on tibial internal/external rotation and anteroposterior (AP)-translation of the lateral and medial compartments were analyzed in a multiple regression model. An increase in tibial internal/external rotation could be demonstrated with decreasing MC width β: −0.30 (95% CI: −0.58 to −0.03) (p = 0.03) during the loaded stance phase of level walking. An increased lateral AP-translation occurred with both a smaller LC flexion circle β: −0.16 (95% CI: −0.28 to −0.05) (p = 0.007) and a deeper MTP β: 0.90 (95% CI: 0.23 to 1.56) (p = 0.01) during the loaded stance phase of level walking. The identified relationship between in vivo tibio-femoral kinematics and bone morphology supports a customized approach and individual assessment of these factors in patients with knee disorders and potentially enhances functional outcomes in anterior cruciate ligament injuries and total knee arthroplasty. Full article

Model-based 3D/2D image registration using single-plane fluoroscopy is a common setup to determine knee joint kinematics, owing to its markerless aspect. However, the approach was subjected to lower accuracies in the determination of out-of-plane motion components. Introducing additional kinematic constraints with an appropriate anatomical representation may help ameliorate the reduced accuracy of single-plane image registration. Therefore, this study aimed to develop and evaluate a multibody model-based tracking (MbMBT) scheme, embedding a personalized kinematic model of the tibiofemoral joint for the measurement of tibiofemoral kinematics. The kinematic model was consisted of three ligaments and an articular contact mechanism. The knee joint activities in six volunteers during isolated knee flexion, lunging, and sit-to-stand motions were recorded with a biplane X-ray imaging system. The tibiofemoral kinematics determined with the MbMBT and mediolateral view fluoroscopic images were compared against those determined using biplane fluoroscopic images. The MbMBT was demonstrated to yield tibiofemoral kinematics with precision values in the range from 0.1 mm to 1.1 mm for translations and from 0.2° to 1.3° for rotations. The constraints provided by the kinematic model were shown to effectively amend the nonphysiological tibiofemoral motion and not compromise the image registration accuracy with the proposed MbMBT scheme. Full article

The effect of friction on nonlinear dynamics and vibration of total knee arthroplasties is yet to be investigated and understood. This research work aims at studying the influence of friction on nonlinear dynamics, friction-induced vibration, and damage of tibiofemoral joints. For this purpose, a spatial dynamic knee model is developed using an asymmetric nonlinear elastic model accounting for knee joint ligaments and a penalty contact model to compute normal contact stresses in the joint while contact detection is treated such that the associated computational time is reduced. Several friction models are considered and embedded in the dynamic model to estimate tangential friction forces in the knee joint. External loads and moments, due to the presence of all soft tissues, e.g., muscles and hip-joint reaction forces, applied to the femoral bone are determined using a musculoskeletal approach. In the post-processing stage, damage, i.e., wear and creep, are estimated using three wear models and an empirical creep formulation, respectively. In addition, a FFT analysis is performed to evaluate likely friction-induced vibration of tibiofemoral joints. Mesh density analysis is performed and the methodology is assessed against outcomes available in the literature. It can be concluded that friction influences not only the tribology, but also dynamics of the knee joint, and friction-induced vibration is likely to take place when the friction coefficient increases. Full article