Joint Stress Research Articles

Residual stress prediction in Ti17 linear friction welds considering inhomogeneous mechanical properties of joints

Microstructural variations of joints occur in linear friction welding, resulting in inhomogeneous mechanical properties that affect the development of residual stress. The mathematical models for elastic moduli and yield strength of Ti17 were firstly developed to obtain the inhomogeneous mechanical properties of joints. Then, the influence of inhomogeneous mechanical properties on residual stress prediction was investigated. The results show that the finite element model considering inhomogeneous mechanical properties accurately captures the bimodal distribution of residual stress and the location of peak stress in joints. Numerically, the peak values of stress are ∼662 and ∼194 MPa along the direction of oscillation and forging, respectively, which is consistent with the result of the contour method.

The application of aquatic resistance exercises in different diseases

Aquatic exercise is an active exercise that make full use of the physical and hydrodynamic characteristics of water in a water environment to achieve a similar strength increase effect as land training, while avoiding the aggravation of joint stress and muscle microdamage caused by repetitive training. It has been widely studied in the field of sports rehabilitation and public fitness, while its form is basically presented in the form of aerobic exercise or interval training, the aquatic resistance exercises are often ignored by people. Due to the influence of the physical characteristics of water, the main form of muscle contraction of athletes performing resistance training in water is similar to isokinetic contraction, and the force used by practitioners is proportional to the resistance of water, which increases the centrifugal load of muscles and greatly reduces the risk of sports injury. In addition to the athletes, aquatic resistance exercises also have certain benefits for other clinical diseases. In this paper, the application of this training in swimming performance, rheumatoid arthritis, postmenopausal osteoporosis and knee osteoarthritis was reviewed in order to improve the clinical understanding and promote its rational application.

Effect of Unanticipated Tasks on Side-Cutting Stability of Lower Extremity with Patellofemoral Pain Syndrome.

Patellofemoral pain syndrome (PFPS) is one of the most common causes of anterior knee pain encountered in the outpatient setting. The purpose of this study was to compare the lower limb biomechanical differences during anticipated and unanticipated side-cutting in athletes with PFPS. Fifteen male basketball players diagnosed with PFPS were enrolled in the study. Participants executed both anticipated and unanticipated 45-degree side-cutting tasks. Motion analysis systems, force plates, and electromyography (EMG) were used to assess the lower limb joint angles, joint moments, joint stiffness, and patellofemoral joint contact forces. Analyzed biomechanical data were used to compare the differences between the two circumstances. Unanticipated side-cutting resulted in significantly increased ankle plantarflexion and dorsiflexion angles, knee abduction and internal rotation angles, and hip abduction angles, as well as heightened knee adduction moments. Additionally, patellofemoral joint contact forces and stress increased, while contact area decreased during unanticipated tasks. Unanticipated movement raises the demands for joint stability and neuromuscular control, increasing injury risks in athletes with PFPS. These findings have practical implications for developing targeted rehabilitation programs and injury prevention strategies.

A novel negative thermal expansion ceramic network interlayer for releasing high residual stress of Cf/SiC heterogeneous brazed joint

Negative thermal expansion (NTE) ceramics have been widely concerned in adjusting the coefficient of thermal expansion (CTE) to release the high residual stress of heterogeneous joint. However, one major problem that needs to be solved is the agglomeration problem caused by excessive ceramic particles addition. In this work, a novel NTE ceramic Sc2W3O12 network interlayer is prepared by the polyurethane template method. The Sc2W3O12 network interlayer with a single NTE phase presents a three-dimensional network structure. The NTE Sc2W3O12 ceramic is uniformly distributed in brazing seam without agglomeration with the help of unique network structure. The active Ti elements play an important role in the interface bonding, reacted with Sc2W3O12 network interlayer and Cf/SiC composites to form Cu3Ti3O and TiC/Ti5Si3 reaction layer, respectively. After introducing Sc2W3O12 network interlayer, the CTE of the composite filler is reduced from 16.6 × 10−6 K−1 to 11.9 × 10−6 K−1, a decrease of 29 %. The highest shear strength of the Cf/SiC heterogeneous joint is reached 130 MPa, which is 5.4 times than that without Sc2W3O12 network interlayer.

The Role of the Lead Hip in Collegiate Baseball Pitching: Implications for Ball Velocity and Upper-Extremity Joint Moments.

Hip flexibility is an important biomechanical factor for a baseball pitcher. However, there have been limited investigations into the association between upper-extremity joint stresses and ball velocity and hip flexibility, as assessed via motion patterns during the pitch. The purpose of this study was to provide a detailed kinematic description of the lead hip during the pitch and determine the association between lead hip motion and both ball velocity and the elbow varus moment. This study was a secondary analysis of the kinematic and kinetic data previously collected on 99 collegiate-level baseball pitchers using standard optoelectronic motion capture. Significant associations were noted between lead hip internal rotation and both peak ball velocity and the elbow varus moment. The data indicated that for every 10° increase in internal lead hip rotation, ball velocity increased by 0.6m/s (P < .001, r2 = .26), and the elbow varus moment increased by 5N·m (P < .001, r2 = .33). The results of this study suggested that internal hip rotation may be an important means of identifying pitchers that may be at risk for future injury.

Clinicoradiological and Arthroscopic Correlation of Meniscal Injuries

Background: Menisci in knee joint serve very important functions of distributing joint stresses and stabilizing the joint. Meniscus tears are on the rise because of increased sports participation. Along with detailed history taking, the physical examination and special investigations such as magnetic resonance imaging (MRI) are required to diagnose meniscal injuries. A diagnostic arthroscopy is considered as the gold standard. Owing to heavy work duties, overdependence on MRI without due clinical examination is on the rise. The aim of our study was to correlate the findings of clinically diagnosed meniscal tears with its radiological and arthroscopic findings and to find out the reliability of clinical examination and MRI in meniscal injuries considering arthroscopy as the gold standard. Materials and Methods: It was a prospective, longitudinal study performed over 12 months. All patients fulfilling inclusion criteria underwent clinical examination and MRI scan; the data obtained were evaluated and correlated with arthroscopic findings. Using necessary equations sensitivity, specificity and accuracy were calculated. Results: The clinical examination showed sensitivity, specificity, and accuracy of 75%, 90.62%, and 83.33%, respectively, when correlated with arthroscopy. MRI scan showed sensitivity, specificity, and accuracy of 82.86%, 92%, and 86.67%, respectively, when correlated with arthroscopy. Conclusion: MRI and clinical examination are comparably sensitive, specific, and accurate for diagnosing meniscal injuries with a subtle preference toward MRI. Author recommends a thorough clinical examination should suffice, but having a MRI scan beforehand is always beneficial in the absence of other concerns to do MRI.

Comparative Analysis of Kinetic Responses and Injury Risk During Landing from 45 cm Height: A Study of Barefoot vs. Sports Shoes Conditions

Jumping and landing biomechanics are closely related to the risk of acute injury due to prolonged exposure to high-ground reaction forces in basketball-like sports, which can lead to lower-limb musculoskeletal injuries in the hip, knee, and ankle. Footwear greatly impacts jumping mechanics, but going barefoot provides a unique perspective on how the human body interacts with the ground. This study aims to find out the kinetic responses during drop landing from 45 cm height with and without sports shoe conditions. Twenty-five healthy young adults were volunteers for this study. Kinetic parameters were recorded and processed by using Quattro Jump force plat and Mars Quarter performance analysis software. Data were presented as mean ± SD values and statistical analysis was performed using statistical software package SPSS-26. The drop landing data of with and without shoe shows scattered parameters with maximum forces of 4706.12N and 5393.04N at 45 cm height, indicating a 66% and 75% risk of metatarsal injury. The stabilization force was 632.64N and 623.64N at 45 cm, reached at 0.58s and 0.66s respectively. Time from Max Force to MFBS Regression analysis indicated a low R-squared value and a random fit plot. In barefoot (without shoe) conditions, the initial contact force, and maximum force were 85.71% and 13.60% higher (250N and 5393.04N respectively) compared to landing with shoes (100N and 4706.12N). However, the stabilization force was higher (632.64N) when landing with shoes compared to landing barefoot (623.64N). As a result, the risk of musculoskeletal injuries and joint stress was higher when landing barefoot due to the higher initial contact force and maximum force. On the other hand, landing with shoes enhances balance and stability due to the higher stabilization force.

Biomechanical Study of Atlanto-occipital Instability in Type II Basilar Invagination: A Finite Element Analysis.

Recent studies indicate that 3 morphological types of atlanto-occipital joint (AOJ) exist in the craniovertebral junction and are associated with type II basilar invagination (BI) and atlanto-occipital instability. However, the actual biomechanical effects remain unclear. This study aims to investigate biomechanical differences among AOJ types I, II, and III, and provide further evidence of atlanto-occipital instability in type II BI. Models of bilateral AOJ containing various AOJ types were created, including I-I, I-II, II-II, II-III, and III-III models, with increasing AOJ dysplasia across models. Then, 1.5 Nm torque simulated cervical motions. The range of motion (ROM), ligament and joint stress, and basion-dental interval (BDI) were analyzed. The C0-1 ROM and accompanying rotational ROM increased progressively from model I-I to model III-III, with the ROM of model III-III showing increases between 27.3% and 123.8% indicating ultra-mobility and instability. In contrast, the C1-2 ROM changes were minimal. Meanwhile, the stress distribution pattern was disrupted; in particular, the C1 superior facet stress was concentrated centrally and decreased substantially across the models. The stress on the C0-1 capsule ligament decreased during cervical flexion and increased during bending and rotating loading. In addition, BDI gradually decreased across the models. Further analysis revealed that the dens showed an increase of 110.1% superiorly and 11.4% posteriorly, indicating an increased risk of spinal cord impingement. Progressive AOJ incongruity critically disrupts supportive tissue loading, enabling incremental atlanto-occipital instability. AOJ dysplasia plays a key biomechanical role in the pathogenesis of type II BI.

Experimental and numerical study on mounting force and withdrawal strength of self-threaded dowels in particleboard

Traditional and alternative joining techniques have been used for many years at the connection points of structural bearing systems. Especially, glued doweled and screwed type mechanical connections are widely used in wooden structures and furniture constructions. Although there are many studies related to the strength of dowel and screw joints, limited papers describe the practical use of self-threaded dowels (STDs) in the joints. In this study, thread geometry effect of the STDs in particleboard (PB) was investigated by determining the mounting force and withdrawal strength values. For this purpose, STDs including three different thread width (0,2 - 0,3 - 0,4 mm) and two different thread length (1 - 2 mm) were designed, produced and tested under static compressive and tensile forces. All STDs were produced with polylactic acid (PLA) by using Layer Plastic Deposition (LPD) method in 3D printing technology. Uniaxial compression tests were performed in order to determine the minimum mounting force while the tension tests were performed for determining the maximum withdrawal force required to put the STDs into the hole and pull out them, respectively. Numerical analysis (FEM) were used to analyze the contact pressures and stresses of the STD joints. Abaqus v6.13-1 software was utilized for the numerical analyses. In addition, multiple regression analysis was carried out to predict the mounting force and withdrawal strength of the STDs. Results showed that the predictive expressions developed provided reasonable estimates for mounting force and withdrawal strength of STDs. According to the statistical analyses; thread width, thread length and their interaction have significantly affected both mounting force and withdrawal strength of STDs. At the end of the experimental and numerical tests, STDs with 0,2 mm width and 2 mm length threads gave the lowest mounting force values, stresses and contact forces. However, the highest withdrawal strength values were obtained from the STDs with 0,3 mm width and 1 mm length threads. According to the results of the study, the optimum STD was the one with 0,3 mm thread width and 2 mm thread length. In conclusion, the STDs can be utilized as an alternative fastener to the conventional glued dowel type joints in PB. However, corner joints constructed of different kinds of wood-based composites and connected with the STDs should be investigated in the future studies.

Lateral meniscus root tear in anterior cruciate ligament injured patients is not associated with increased rotatory knee laxity: A quantitative pivot shift analysis

ObjectivesBiomechanical investigations conducted in vitro have elucidated the detrimental impact of lateral meniscus posterior root (LMPR) tears on knee contact pressures in the anterior cruciate ligament (ACL)-injured knee. Nevertheless, the influence of LMPR tears on the kinematics of ACL-injured patients remains ambiguous. The purpose of this study was to assess the impact of LMPR tears on anteroposterior and rotatory knee laxity employing a clinically validated quantitative pivot shift (QPS) analysis system. MethodsPatients with ACL injury recruited in a prospective ACL registry spanning from 2012 to 2020 were retrospectively screened for eligibility. Criteria for inclusion encompassed complete primary ACL tears, absence of concurrent ligamentous or osseous injuries requiring operative treatment, and no prior knee surgeries.Patients were assigned to two cohorts based on the presence (LMPR+) or absence (LMPR-) of an LMPR tear concomitant with ACL injury. Each patient underwent a standardized PS test, measurement of anterior tibial translation (ATT) (mm) using the Rolimeter, and QPS (mm) with a tablet-based image analysis system (PIVOT App). Comparative analyses of categorical variables were performed using the Fisher exact and Chi-square tests, while non-normally distributed continuous variables were compared between groups with the Mann–Whitney U test. Alfa was set at 0.05. ResultsA total of 99 patients were included in the study, of which 22 were assigned to the LMPR+ and 77 to the LMPR- group. Tear depth was considered partial in 13 (59%) patients and full in 9 (41%) patients. The prevalence of medial meniscus tears was greater in the LMPR+ (n ​= ​16, 73%) compared with the LMPR- (n ​= ​33, 43%) group (p ​= ​0.01). No difference was observed in ATT measured with the Rolimeter (p ​= ​0.63). Similarly, no difference was found in QPS between the LMPR+ (2.3 ​mm) and the LMPR- (1.9 ​mm) group (p ​= ​0.08). ConclusionUtilizing QPS in this investigation, LMPR tears do not significantly increase ATT or rotatory knee laxity. Consequently, although repairing LMRT associated with ACL injuries may be advisable for minimizing joint stress, their impact on controlling the PS in patients remains uncertain. Level of evidenceIII, retrospective comparative study.

Effects of Aging on Patellofemoral Joint Stress during Stair Negotiation on Challenging Surfaces.

This study examined the effect of age and surface on patellofemoral joint (PFJ) stress magnitude and waveform during stair ascent and descent tasks. A total of 12 young and 12 older adults had knee biomechanics quantified while they ascended and descended stairs on normal, slick, and uneven surfaces. The peak of stance (0-100%) PFJ stress and associated components were submitted to a two-way repeated measures ANOVA, while the PFJ stress waveform was submitted to statistical parametric mapping two-way ANOVA. During stair ascent, older adults exhibited greater PFJ stress waveforms, from 55 to 59% and 74 to 84% of stance (p < 0.001) as well as greater PFJ stress-time integral across stance (p = 0.003), and later peak PFJ stress, than young adults (p = 0.002). When ascending on the uneven surface, participants exhibited smaller PFJ stress from 9 to 24% of stance compared to the normal surface, but greater PFJ stress from 75 to 88% and from 63 to 68% of stance (p < 0.001) as well as greater PFJ stress-time integrals compared to normal and slick surfaces (p < 0.032). During stair descent, older adults exhibited a smaller PFJ contact area range (p = 0.034) and peak knee flexion angle (p = 0.022) than young adults. When descending on the slick surface, participants exhibited smaller PFJ stress from 5 to 18% of stance, but greater stress, from 92 to 98% of stance (both: p < 0.001), compared to the normal surface. Negotiating slick and uneven stairs may produce knee biomechanics that increase PFJ stress, and the larger, later PFJ stress exhibited by older adults may further increase their risk of PFJ pain.

Development of a theory-monitoring integrated structure joints assessment method of prefabricated underground stations

Prefabricated assembly structures have been extensively applied for the construction of low carbon and cost effective underground subway stations in China. Engineers faced significant challenges in dealing with the assessment of mechanical performance of structures joints within prefabricated underground station (PUS) structures during construction process. Manual assembly of large-scale prefabricated structures may lead to significant disturbance of structures joints, resulting in structures joints failure in construction process or even water leakage in maintenance of underground stations. To address these issues, this study proposed an integrated theory-monitoring method for joint performance assessment. The initial step involved the establishment of a fiber optical sensors (FOS) monitoring system for PUS joints. A joint performance assessment module was then developed utilizing the Joint Interfaces Contact Model (JICM) and was subsequently integrated into monitoring system, forming a joint performance assessment method, namely FOS-JICM (FOJI). A case study was finally conducted on a Shenzhen pipe jacking PUS to evaluate the effectiveness of FOJI. Main research findings of this study include (a) FOS monitoring system demonstrated excellent adaptability, accuracy, and real-time performance in practical applications; (b) FOS monitoring system effectively captured joint deformation and stress evolution throughout the entire construction process, providing insights into the impact of complex geological conditions and box culverts on joint behavior; (c) FOJI, with its integration of the JICM module, enabled safety assessment of joint performance during pipe jacking process; (d) FOJI successfully identified joint damage, offering valuable guidance for engineering restoration and protective measures. It facilitated prompt updates and adjustments based on the actual construction conditions, establishing a cycle mechanism for safety protection. These achievements not only establish a theoretical foundation for ensuring the construction safety of PUS joints but also present substantial practical application value.

Health behaviours and work-related musculoskeletal pain among polish physiotherapists and nurses.

Physiotherapists and nurses play crucial roles in healthcare, often requiring them to adopt physically demanding positions. However, these positions can lead to joint stress and an increased risk of injury, as well as work-related musculoskeletal disorders (WRMSDs). These disorders can significantly impact the performance of their duties, which can negatively affect patient recovery. This study assessed and compared health behaviour and work-related musculoskeletal pain among Polish physiotherapists and nurses. The study encompassed a group of 304 participants. The methodology consisted of a survey addressing pain-related questions and the Health Behaviour Inventory (HBI). The HBI evaluates health behaviour in four categories. The average HBI score was 5.05 (±1.96) points for physiotherapists and 4.50 (±1.86) points for nurses (P = .01). When analysing the HBI components, a statistically significant difference was observed in positive mental attitude and health practices (P < .05). Regarding work-related musculoskeletal pain, 92% of nurses and 79% of physiotherapists reported experiencing pain while working (P < .01). Pain intensity, measured with the VAS, was 3.77 (±2.37) for physiotherapists and 4.73 (SD 2.04) for nurses (P < .01). Physiotherapists more often suffered from upper limb pain (57% vs 49%), while nurses experienced middle/lower back pain (82% vs 63%) and lower extremity pain (38% vs 23%) more frequently. Both professional groups experience WRMSDs, with nurses suffering more regularly and severely. In contrast, physiotherapists exhibit superior health behaviour practices, potentially mitigating musculoskeletal pain. Nonetheless, the prevalence of pain related to WRMSDs remains alarmingly high in both professions.

Test on progressive collapse of steel moment-resisting frame with upper-and-lower flange angle steel connection

Both of test and numerical simulation methods are employed to study the vertical progressive collapse and collapse assessment methods of steel frame under accidental loads. Firstly, a steel frame collapse test model with a geometric similarity ratio of 1:1.5 is designed and manufactured. The ends of column of test model is fixed. The upper and lower flange angle steel connection is used. The far end of the beam is constrained by a controllable sliding hinge support. The various stages of vertical progressive collapse of structures are simulated by a large displacement loads applied at the far end of the beam. The main focus of the testing is to examine the stress and deformation of beam and joint at various stages, particularly the development of stress and deformation in the angle steel attached to the beam-column connection. The development law of collapse load-displacement curve, joint rotation, beam strain, and angle steel strain are analyzed. The structural resistance mechanism and the transformation relationship between resistance mechanisms during collapse are studied. Subsequently, the relationship between the structural dynamic increase factor curve and the structural collapse process is analyzed using finite element method. The results show that the strain of angle steels can better reflect the destruction and deformation process of substructure during the collapse, the collapse resistance mechanism of structure, and the transition between resistance mechanisms.With the help of the characteristic points on the structural dynamic increase factor curve, the collapse limit state of structure can be reliably determined.

Effects of different sensory integration tasks on the biomechanical characteristics of the lower limb during walking in patients with patellofemoral pain.

This study aimed to analyze the biomechanical characteristics of the lower limb in patients with patellofemoral pain (PFP) while walking under different sensory integration tasks and elucidate the relationship between these biomechanical characteristics and patellofemoral joint stress (PFJS). Our study's findings may provide insights which could help to establish new approaches to treat and prevent PFP. Overall, 28 male university students presenting with PFP were enrolled in this study. The kinematic and kinetic data of the participants during walking were collected. The effects of different sensory integration tasks including baseline (BL), Tactile integration task (TIT), listening integration task (LIT), visual integration task (VIT) on the biomechanical characteristics of the lower limb were examined using a One-way repeated measures ANOVA. The relationship between the aforementioned biomechanical characteristics and PFJS was investigated using Pearson correlation analysis. The increased hip flexion angle (P = 0.016), increased knee extension moment (P = 0.047), decreased step length (P < 0.001), decreased knee flexion angle (P = 0.010), and decreased cadence (P < 0.001) exhibited by patients with PFP while performing a VIT were associated with increased patellofemoral joint stress. The reduced cadence (P < 0.050) achieved by patients with PFP when performing LIT were associated with increased patellofemoral joint stress. VIT significantly influenced lower limb movement patterns during walking in patients with PFP. Specifically, the increased hip flexion angle, increased knee extension moment, decreased knee flexion angle, and decreased cadence resulting from this task may have increased PFJS and may have contributed to the recurrence of PFP. Similarly, patients with PFP often demonstrate a reduction in cadence when exposed to TIT and LIT. This may be the main trigger for increased PFJS under TIT and LIT.

Analysis of Knuckle Joint for Structural Steel, Aluminium Alloy, And Titanium Alloy

Abstract—The goal of this research is to investigate and determine the stresses in a knuckle joint using steady state analysis, with the objective of identifying the optimal material for the project. Three different materials, namely structural steel, aluminium alloy, and titanium alloy are analyzed for the knuckle joint. The study focuses on a knuckle joint designed for an applied force of 25 KN. Finite Element Analysis (FEA) results for tensile loading are compared and validated with total deformation. The findings indicate that the knuckle joint made of titanium alloy exhibits the lowest stresses, while the knuckle joint made of structural steel is capable of sustaining the highest tensile load without failure. Keywords- Knuckle Joint, FEM, stress analysis, Titanium alloy, aluminium alloy, structural steel.

Comparative analysis of internal fixation modalities for PER type IV ankle fractures: a finite element study

BackgroundThere are many options for the surgical treatment of pronation external rotation (PER) type IV ankle fractures, including the use of fibular plates and screws, the aim of this study was to investigate the biomechanical stability and safety of different internal fixation methods for PER type IV ankle fractures via finite element analysis.MethodsA three-dimensional finite element model of the ankle joint and the whole foot of a healthy 26-years-old adult male was established and validated based on computed tomography images of his lower limb, and a computer-aided design was used to produce a PER type IV ankle fracture and plate and screw model. Four different internal fixation modes were simulated, including a (all ankle fixation—utilizing a fibular plate and screws for comprehensive stabilization of the ankle), b (inferior tibiofibular joint fixation + all ankle fixation), c (inferior tibiofibular joint fixation + unfixed anterior ankle), and d (inferior tibiofibular joint fixation + unfixed anterior and posterior ankles). The results of the four different fixation methods were compared via finite element analysis, and the von Mises stresses. The displacements of the four different fixation methods were analyzed as the output indices.ResultsThere were no significant differences between the results of using fibular plates and screws and the displacement of fracture breaks among the four internal fixation modalities. The von Mises stress in the tibiotalar joint, median ankle, posterior ankle, and anterior ankle was minimized in the working condition of d, d, b, and d respectively. The von Mises stress in the fibular plate and screws was minimized in the working condition of a. The von Mises stress in the distal fibula was minimized in the working condition of a. However, the stress was mainly concentrated at the attachment point of the inferior tibiofibular anterior ligament, and in the working condition with inferior tibiofibular joint fixation, the stress was significantly concentrated in the inferior tibiofibular joint screw in all the fibular plates and screws.ConclusionsThe results of this study demonstrate the feasibility of using finite element analysis to compare the biomechanical stability and safety of four configurations of fibular plates and screws for treating PER type IV ankle fractures. All four modalities provided comparable biomechanical stability and safety, showing no significant differences. However, the current limitations of the finite element analysis methodology preclude specific clinical inferences. Further refinement of the methodology in future studies is necessary to enable reliable clinical applications.

Effects of attentional focus strategies in drop landing biomechanics of individuals with unilateral functional ankle instability.

Functional Ankle Instability (FAI) is a pervasive condition that can emerge following inadequate management of lateral ankle sprains. It is hallmarked by chronic joint instability and a subsequent deterioration in physical performance. The modulation of motor patterns through attentional focus is a well-established concept in the realm of motor learning and performance optimization. However, the precise manner in which attentional focus can rehabilitate or refine movement patterns in individuals with FAI remains to be fully elucidated. The primary aim of this study was to evaluate the impact of attentional focus strategies on the biomechanics of single-leg drop landing movements among individuals with FAI. Eighteen males with unilateral FAI were recruited. Kinematic and kinetic data were collected using an infrared three-dimensional motion capture system and force plates. Participants performed single-leg drop landing tasks under no focus (baseline), internal focus (IF), and external focus (EF) conditions. Biomechanical characteristics, including joint angles, ground reaction forces, and leg stiffness, were assessed. A 2 × 3 [side (unstable and stable) × focus (baseline, IF, and EF)] Repeated Measures Analysis of Variance (RM-ANOVA) analyzed the effects of attentional focus on biomechanical variables in individuals with FAI. No significant interaction effects were observed in this study. At peak vertical ground reaction force (vGRF), the knee flexion angle was significantly influenced by attentional focus, with a markedly greater angle under EF compared to IF (p < 0.001). Additionally, at peak vGRF, the ankle joint plantarflexion angle was significantly smaller with EF than with IF (p < 0.001). Significant main effects of focus were found for peak vGRF and the time to reach peak vGRF, with higher peak vGRF values observed under baseline and IF conditions compared to EF (p < 0.001). Participants reached peak vGRF more quickly under IF (p < 0.001). Leg Stiffness (kleg) was significantly higher under IF compared to EF (p = 0.001). IF enhances joint stability in FAI, whereas EF promotes a conservative landing strategy with increased knee flexion, dispersing impact and minimizing joint stress. Integrating these strategies into FAI rehabilitation programs can optimize lower limb biomechanics and reduce the risk of reinjury.

Theoretical modeling and error analysis of a compliant Y-shaped mechanism including beam joint stiffness and stress topology for size optimization of six-axis force/moment sensors

Theoretical modeling and error analysis of a compliant Y-shaped mechanism including beam joint stiffness and stress topology for size optimization of six-axis force/moment sensors

A bioactive supramolecular and covalent polymer scaffold for cartilage repair in a sheep model

Regeneration of hyaline cartilage in human-sized joints remains a clinical challenge, and it is a critical unmet need that would contribute to longer healthspans. Injectable scaffolds for cartilage repair that integrate both bioactivity and sufficiently robust physical properties to withstand joint stresses offer a promising strategy. We report here on a hybrid biomaterial that combines a bioactive peptide amphiphile supramolecular polymer that specifically binds the chondrogenic cytokine transforming growth factor β-1 (TGFβ-1) and crosslinked hyaluronic acid microgels that drive formation of filament bundles, a hierarchical motif common in natural musculoskeletal tissues. The scaffold is an injectable slurry that generates a porous rubbery material when exposed to calcium ions once placed in cartilage defects. The hybrid material was found to support in vitro chondrogenic differentiation of encapsulated stem cells in response to sustained delivery of TGFβ-1. Using a sheep model, we implanted the scaffold in shallow osteochondral defects and found it can remain localized in mechanically active joints. Evaluation of resected joints showed significantly improved repair of hyaline cartilage in osteochondral defects injected with the scaffold relative to defects injected with the growth factor alone, including implantation in the load-bearing femoral condyle. These results demonstrate the potential of the hybrid biomimetic scaffold as a niche to favor cartilage repair in mechanically active joints using a clinically relevant large-animal model.