Knee joint loading during gait in healthy controls and individuals with knee osteoarthritis

Walking Pole Gait to Reduce Joint Loading post Total Knee Athroplasty: Musculoskeletal modeling Approach

Excessive knee contact loading is precursor to osteoarthritis and related knee ailment leading to knee athroplasty. Reducing contact loading through gait modifications using assisted pole walking offers noninvasive process of medial load offloading at knee joint. In this paper, we evaluate the efficacy of different configuration of pole walking for reducing contact force at the knee joint through musculoskeletal (MSK) modeling. We have developed a musculoskeletal model for a subject with knee athroplasty utilizing in-vivo implant data and computed tibio-femoral contact force for different pole walking conditions to evaluate the best possible configuration for guiding rehabilitation, correlated with different gait phases. Effect of gait speed variation on knee contact force, hip joint dynamics and muscle forces are simulated using the developed MSK model. Results indicate some interesting trend of load reduction, dependent on loading phases pertaining to different pole configuration. Insights gained from the simulation can aid in designing personalized rehabilitation therapy for subjects suffering from Osteoarthritis.

Effects of resistance training on gait velocity and knee adduction moment in knee osteoarthritis patients: a systematic review and meta-analysis

The systematic review aimed to analyze the effects of resistance training in knee osteoarthritis (OA) rehabilitation from a biomechanical perspective. A meta-analysis was performed to determine the potential benefits of resistance training on patients with knee OA. Relevant studies based on the inclusion and exclusion criteria were selected from CENTRAL, PubMed, Scopus, and Web of Science databases inception to August 2020. Outcome measures included gait velocity and knee adduction moment (KAM). The mean differences of the data with a 95% confidence interval were analyzed using STATA 15.1 software The search identified eight studies that satisfied all the inclusion criteria, in which 164 patients were involved in gait velocity studies and another 122 patients were part of KAM studies. Analysis of the pooled data showed that resistance training significantly improved the gait velocity in patients with knee OA (p < 0.01, z = 2.73), ES (95% CI) = 0.03 (0.01, 0.06) m/s. However, resistance training had no significant effect on improving KAM in patients with knee OA (p = 0.98, z = 0.03), ES (95% CI) = 0.00 (− 0.16, 0.16) percentage of body weight × height (%BW × Ht). Therefore, resistance training may enhance gait velocity but not KAM in knee OA patients. The protocol was registered at PROSPERO (registration number: CRD42020204897).

Development and Functional Testing of An Unloading Concept for Knee Osteoarthritis Patients: A Pilot Study

This paper presents a knee brace design that applies an extension moment to unload the muscles in stance phase during gait, and thereby the knee, as alternative to conventional valgus braces for knee osteoarthritis patients. The concept was tested on one healthy subject during normal gait with a prototype, which was designed to activate and deactivate in order to apply the extension moment in the stance phase only and hereby avoid any interference during the swing phase. Electromyography measurements and musculoskeletal models were used to evaluate the brace effects on muscle activation and knee compressive forces respectively. Simulations predicted an ideal reduction of up to 36%, whereas experimental tests revealed a reduction of up to 24% with the current prototype. The prototype brace also reduced the knee joint force impulse up to 9% and EMG peak signal of the vasti muscles with up to 19%. Due to these reductions on a healthy subject, this bracing approach seem promising for reducing knee loads during normal gait. However, further clinical experiments on knee osteoarthritis patients are required to evaluate the effect on both pain and disease progression.

An in vitro investigation to understand the synergistic role of MMPs-1 and 9 on articular cartilage biomechanical properties

Matrix metalloproteinases (MMPs) play a crucial role in enzymatically digesting cartilage extracellular matrix (ECM) components, resulting in degraded cartilage with altered mechanical loading capacity. Overexpression of MMPs is often caused by trauma, physiologic conditions and by disease. To understand the synergistic impact MMPs have on cartilage biomechanical properties, MMPs from two subfamilies: collagenase (MMP-1) and gelatinase (MMP-9) were investigated in this study. Three different ratios of MMP-1 (c) and MMP-9 (g), c1:g1, c3:g1 and c1:g3 were considered to develop a degradation model. Thirty samples, harvested from bovine femoral condyles, were treated in groups of 10 with one concentration of enzyme mixture. Each sample was tested in a healthy state prior to introducing degradative enzymes to establish a baseline. Samples were subjected to indentation loading up to 20% bulk strain. Both control and treated samples were mechanically and histologically assessed to determine the impact of degradation. Young's modulus and peak load of the tissue under indentation were compared between the control and degraded cartilage explants. Cartilage degraded with the c3:g1 enzyme concentration resulted in maximum 33% reduction in stiffness and peak load compared to the other two concentrations. The abundance of collagenase is more responsible for cartilage degradation and reduced mechanical integrity.

Gait Adaptations at 8 Years After Reconstruction of Unilateral Isolated and Combined Posterior Cruciate Ligament Injuries

BACKGROUND

It remains unclear how posterior cruciate ligament (PCL) reconstruction influences long-term lower extremity joint biomechanics.

PURPOSE

To determine whether patients who underwent PCL reconstruction exhibited long-term alterations in lower limb gait mechanics.

STUDY DESIGN

Controlled laboratory study.

METHODS

A total of 26 patients underwent gait analyses at 8.2 ± 2.6 years after primary unilateral PCL reconstruction. Sex- and age-matched healthy controls were analyzed for comparison. Gait data were collected using motion capture and force plates. Hip, knee, and ankle angles and moments were compared during initial contact, early stance, and late stance for the reconstructed and uninjured contralateral limbs of patients who underwent PCL reconstruction (PCL group) as well as the limbs of healthy control participants (CON group).

RESULTS

No side-to-side kinematic differences were noted between the reconstructed and contralateral limbs of the PCL group; some trivial differences were noted in knee and hip moments. However, major differences between the PCL and CON groups occurred at the knee. Reconstructed and contralateral limbs of the PCL group exhibited larger knee flexion angles during initial contact (Δ = 7.0° [P < .001] and Δ = 6.9° [P < .001], respectively), early stance (Δ = 5.8° [P = .003] and Δ = 6.7° [P < .001], respectively), and late stance (Δ = 7.9° [P < .001] and Δ = 8.0° [P < .001], respectively) compared with the CON group. During early stance, contralateral limbs of the PCL group displayed larger knee flexion moments (Δ = 0.20 N·m/kg; P = .014) compared with the CON group, and both reconstructed (Δ = 0.05 N·m/kg; P = .027) and contralateral (Δ = 0.07 N·m/kg; P = .001) limbs of the PCL group exhibited larger knee external rotation moments compared with the CON group. During late stance, reconstructed and contralateral limbs of the PCL group exhibited smaller knee extension moments (Δ = 0.24 N·m/kg [P < .001] and Δ = 0.26 N·m/kg [P < .001], respectively) and knee internal rotation moments (Δ = 0.06 N·m/kg [P < .001] and Δ = 0.06 N·m/kg [P < .001], respectively) compared with the CON group. No discrepancies were observed at the hip; minimal differences were noted in sagittal-plane ankle mechanics.

CONCLUSION

Patients who underwent PCL reconstruction generally exhibited bilateral gait symmetry at 8 years after surgery. However, they exhibited important biomechanical deviations in both knees compared with healthy controls. These modifications likely reflect adaptive gait strategies to protect the PCL after reconstruction.

CLINICAL RELEVANCE

Long-term follow-up analyses of patients who underwent PCL reconstruction should not use the uninjured contralateral limb as a "healthy" reference, as it also exhibits mechanical differences compared with controls. Results could inform the development of neuromuscular and strength training programs targeting the restoration of knee biomechanics similar to healthy controls to prevent early-onset degeneration that is frequently associated with altered biomechanics.

Enhanced matrix production by cocultivated human stem cells and chondrocytes under concurrent mechanical strain

Conventional treatments of osteoarthritis have failed to re-build functional articular cartilage. Tissue engineering clinical treatments for osteoarthritis, including autologous chondrocyte implantation, provides an alternative approach by injecting a cell suspension to fill lesions within the cartilage in osteoarthritic knees. The success of chondrocyte implantation relies on the availability of chondrogenic cell lines, and their resilience to high mechanical loading. We hypothesize we can reduce the numbers of human articular chondrocytes necessary for a treatment by supplementing cultures with human adipose-derived stem cells, in which stem cells will have protective and stimulatory effects on mixed cultures when exposed to high mechanical loads, and in which coculture will enhance production of requisite extracellular matrix proteins over those produced by stretched chondrocytes alone. In this work, adipose-derived stem cells and articular chondrocytes were cultured separately or cocultivated at ratios of 3:1, 1:1, and 1:3 in static plates or under excessive cyclic tensile strain of 10% and results were compared to culturing of both cell types alone with and without cyclic strain. Results indicate 75% of chondrocytes in engineered articular cartilage can be replaced with stem cells with enhanced collagen over all culture conditions and glycosaminoglycan content over stretched cultures of chondrocytes. This can be done without observing adverse effects on cell viability. Collagen and glycosaminoglycan secretion, when compared to chondrocyte alone under 10% strain, was enhanced 6.1- and 2-fold, respectively, by chondrocytes cocultivated with stem cells at a ratio of 1:3.

Effect of High Tibial Osteotomy on the Distribution of Subchondral Bone Density Across the Proximal Tibial Articular Surface of the Knee With Medial Compartment Osteoarthritis

BACKGROUND

The effect of high tibial osteotomy (HTO) on the stress distribution across the knee joint is not completely understood. Subchondral bone density is considered to reflect the pattern of stress distribution across a joint surface.

PURPOSE

To assess the distribution of subchondral bone density across the proximal tibia in nonarthritic knees and in the knees of patients with osteoarthritis (OA) before and after HTO.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

We retrospectively collected radiological and computed tomography data from 16 patients without OA (control group) and 17 patients with OA. Data from the OA group were collected before and 1.5 years after HTO. Subchondral bone density of the proximal tibia was assessed with computed tomography-osteoabsorptiometry. The locations and percentages represented by high-density areas (HDAs) on the articular surface were quantitatively analyzed.

RESULTS

The ratio of the HDA of the medial compartment to the total HDA (medial ratio) was significantly higher in the preoperative OA group (mean, 80.1%) than in the control group (61.3%) (P < .001). After HTO, the medial ratio decreased significantly to 75.1% (P = .035 in comparison with preoperative values) and was significantly correlated with the hip-knee-ankle angle in both groups: control (r = -0.551; P = .033) and OA (r = -0.528; P = .043). The change in medial ratio after HTO was significantly correlated with the change in hip-knee-ankle angle (r = 0.587; P = .035). In the medial compartment, the HDA in the most lateral region of 4 subregions increased after HTO, but that in 3 medial subregions decreased.

CONCLUSION

In this exploratory study, HTO shifted the HDA of the medial compartment of the proximal tibial articular surface toward the lateral compartment. In contrast, the HDA of the most lateral region of the medial compartment increased after HTO. This change in subchondral bone density may result from the change in stress distribution.

Knee loading in OA subjects is correlated to flexion and adduction moments and to contact point locations

This study evaluated the association of contact point locations with the knee medial and lateral contact force (F_med, F_lat) alterations in OA and healthy subjects. A musculoskeletal model of the lower limb with subject-specific tibiofemoral contact point trajectories was used to estimate the F_med and F_lat in ten healthy and twelve OA subjects during treadmill gait. Regression analyses were performed to evaluate the correlation of the contact point locations, knee adduction moment (KAM), knee flexion moment (KFM), frontal plane alignment, and gait speed with the F_med and F_lat. Medial contact point locations in the medial–lateral direction showed a poor correlation with the F_med in OA (R² = 0.13, p = 0.01) and healthy (R² = 0.24, p = 0.001) subjects. Anterior–posterior location of the contact points also showed a poor correlation with the F_med of OA subjects (R² = 0.32, p < 0.001). Across all subjects, KAM and KFM remained the best predictors of the F_med and F_lat, respectively (R² between 0.62 and 0.69). Results suggest different mechanisms of contact force distribution in OA joints. The variations in the location of the contact points participate partially to explains the F_med variations in OA subjects together with the KFM and KAM.

Can an OA Knee Brace Effectively Offload the Medial Condyle? An In Vivo Fluoroscopic Study

BACKGROUND

Previous studies evaluating the effectiveness of OA offloading knee braces focused on qualitative results. The objective of this study was to analyze the effectiveness of an off-loading knee brace with respect to in vivo three-dimensional knee kinematics to quantitatively measure the changes in medial joint space and relative bone alignment when wearing the brace.

METHODS

Twenty subjects diagnosed with medial compartmental joint space narrowing and varus deformity due to OA were recruited. During fluoroscopic surveillance, subjects performed normal gait on a treadmill with and without the brace. Images were sequenced at heel-strike and mid-stance during the weight-bearing portion of gait. 3D-to-2D image registration was performed on each subject using 3D bone models derived from CT segmentation and 3D ultrasound scans.

RESULTS

Medial joint space was to increase when the brace was applied in all subjects (1.6 ± 0.7 mm at heel-strike, 1.6 ± 0.8 mm at mid-stance) and was statistically significant (P < .001). It was also found that sixteen of the twenty subjects experienced a medial joint space increase of more than 1.0 mm during heel-strike while thirteen of twenty experienced this change at mid-stance. While wearing the brace, over half of the subjects experienced a valgus correction to their alignment.

CONCLUSIONS

All subjects in this study experienced a positive change in the medial joint space when wearing the offloading knee brace. In addition, many subjects also saw joint space values representative of previously documented, nonosteoarthritic subjects and valgus changes in bone alignment more akin to the normal knee.

Transversus abdominis activation does not alter gait impairments in patients with and without knee osteoarthritis

BACKGROUND

Knee osteoarthritis accounts for more years of disability than all other forms of osteoarthritis combined. Gait kinetic and kinematic changes, in addition to reduced gait speed, are commonly observed. This study investigates whether core activation, which modifies lower extremity movement in young, active populations, can alter the gait and baseline core activation of those with knee osteoarthritis as compared to controls, and alter osteoarthritic knee pain.

METHODS

Forty-four participants (22 controls and 22 with knee osteoarthritis) underwent biomechanical gait assessment, examining kinetic and kinematic variables, in addition to gait speed, with and without volitional transversus abdominis activation. Surface electromyography was used to measure baseline transversus abdominis activation under both conditions. Knee pain ratings were examined for those with knee osteoarthritis.

FINDINGS

No significant biomechanical differences were observed within groups, or in the time/group interaction. Between-groups kinetic (time to first peak ground reaction force and amplitude of second peak ground reaction force) and gait speed differences were observed under both conditions. There were no differences in baseline electromyography activation between or within-groups, or within-group for self-reported pain for the osteoarthritic group.

INTERPRETATION

Although previous studies have shown the benefit of core activation in correcting lower extremity movement patterns and kinetic loading in young, athletic populations, this study is the first to show this is not the case for persons with knee osteoarthritis. Future studies should examine the value of a progressive core stabilization program, of sufficient dose and mode, in correcting the observed gait differences in those with knee osteoarthritis.

CLINICAL TRIAL REGISTRATION NUMBER

NCT03776981.

Parametric Study of a Triboelectric Transducer in Total Knee Replacement Application

Triboelectric energy harvesting is a relatively new technology showing promise for biomedical applications. This study investigates a triboelectric energy transducer for potential applications in total knee replacement (TKR) both as an energy harvester and a sensor. The sensor can be used to monitor loads at the knee joint. The proposed transducer generates an electrical signal that is directly related to the periodic mechanical load from walking. The proportionality between the generated electrical signal and the load transferred to the knee enables triboelectric transducers to be used as self-powered active load sensors. We analyzed the performance of a triboelectric transducer when subjected to simulated gait loading on a joint motion simulator. Two different designs were evaluated, one made of Titanium on Aluminum, (Ti-PDMS-Al), and the other made of Titanium on Titanium, (Ti-PDMS-Ti). The Ti-PDMS-Ti design generates more power than Ti-PDMS-Al and was used to optimize the structural parameters. Our analysis found these optimal parameters for the Ti-PDMS-Ti design: external resistance of 304 MΩ, a gap of 550 μm, and a thickness of the triboelectric layer of 50 μm. Those parameters were optimized by varying resistance, gap, and the thickness while measuring the power outputs. Using the optimized parameters, the transducer was tested under different axial loads to check the viability of the harvester to act as a self-powered load sensor to estimate the knee loads. The forces transmitted across the knee joint during activities of daily living can be directly measured and used for self-powering, which can lead to improving the total knee implant functions.

Wearable Inertial Sensors for Gait Analysis in Adults with Osteoarthritis-A Scoping Review

Our objective was to conduct a scoping review which summarizes the growing body of literature using wearable inertial sensors for gait analysis in lower limb osteoarthritis. We searched six databases using predetermined search terms which highlighted the broad areas of inertial sensors, gait, and osteoarthritis. Two authors independently conducted title and abstract reviews, followed by two authors independently completing full-text screenings. Study quality was also assessed by two independent raters and data were extracted by one reviewer in areas such as study design, osteoarthritis sample, protocols, and inertial sensor outcomes. A total of 72 articles were included, which studied the gait of 2159 adults with osteoarthritis (OA) using inertial sensors. The most common location of OA studied was the knee (n = 46), followed by the hip (n = 22), and the ankle (n = 7). The back (n = 41) and the shank (n = 40) were the most common placements for inertial sensors. The three most prevalent biomechanical outcomes studied were: mean spatiotemporal parameters (n = 45), segment or joint angles (n = 33), and linear acceleration magnitudes (n = 22). Our findings demonstrate exceptional growth in this field in the last 5 years. Nevertheless, there remains a need for more longitudinal study designs, patient-specific models, free-living assessments, and a push for "Code Reuse" to maximize the unique capabilities of these devices and ultimately improve how we diagnose and treat this debilitating disease.

Characterization of regional meniscal cell and chondrocyte phenotypes and chondrogenic differentiation with histological analysis in osteoarthritic donor-matched tissues

Meniscus degeneration is closely related to the progression of knee osteoarthritis (OA). However, there is currently a lack of quantitative and objective metrics to assess OA meniscal cell phenotypes. In this study we investigated the phenotypic markers and chondrogenic potency of avascular and vascular meniscal cells and chondrocytes from medial OA knee joints (n = 10). Flow cytometry results showed that a significantly greater percentage of meniscal cells were positive for CD49b, CD49c and CD166 compared to donor-matched chondrocytes after 14 days in monolayer culture. The integrins, CD49b and CD29, were expressed at a significantly higher level on avascular meniscal cells derived from tissues with a more degenerated inner border than non-degenerate menisci, suggesting that the integrin family may play an important role in meniscus OA pathology. Collagen fibres arranged in a "tree-like" formation within the meniscus appeared to have less blood vessels associated with them in the vascular region of the most degenerate menisci, which may indicate that such structures are involved in the pathological process. We have demonstrated that meniscal cells derived from the lateral meniscus in medial OA patients have chondrogenic capacity in vitro and hence could represent a potential cell source to consider for meniscus tissue engineering.

A Systematic Review of the Associations Between Inverse Dynamics and Musculoskeletal Modeling to Investigate Joint Loading in a Clinical Environment

The assessment of knee or hip joint loading by external joint moments is mainly used to draw conclusions on clinical decision making. However, the correlation between internal and external loads has not been systematically analyzed. This systematic review aims, therefore, to clarify the relationship between external and internal joint loading measures during gait. A systematic database search was performed to identify appropriate studies for inclusion. In total, 4,554 articles were identified, while 17 articles were finally included in data extraction. External joint loading parameters were calculated using the inverse dynamics approach and internal joint loading parameters by musculoskeletal modeling or instrumented prosthesis. It was found that the medial and total knee joint contact forces as well as hip joint contact forces in the first half of stance can be well predicted using external joint moments in the frontal plane, which is further improved by including the sagittal joint moment. Worse correlations were found for the peak in the second half of stance as well as for internal lateral knee joint contact forces. The estimation of external joint moments is useful for a general statement about the peak in the first half of stance or for the maximal loading. Nevertheless, when investigating diseases as valgus malalignment, the estimation of lateral knee joint contact forces is necessary for clinical decision making because external joint moments could not predict the lateral knee joint loading sufficient enough. Dependent on the clinical question, either estimating the external joint moments by inverse dynamics or internal joint contact forces by musculoskeletal modeling should be used.

Real-Time Prediction of Joint Forces by Motion Capture and Machine Learning

Conventional biomechanical modelling approaches involve the solution of large systems of equations that encode the complex mathematical representation of human motion and skeletal structure. To improve stability and computational speed, being a common bottleneck in current approaches, we apply machine learning to train surrogate models and to predict in near real-time, previously calculated medial and lateral knee contact forces (KCFs) of 54 young and elderly participants during treadmill walking in a speed range of 3 to 7 km/h. Predictions are obtained by fusing optical motion capture and musculoskeletal modeling-derived kinematic and force variables, into regression models using artificial neural networks (ANNs) and support vector regression (SVR). Training schemes included either data from all subjects (LeaveTrialsOut) or only from a portion of them (LeaveSubjectsOut), in combination with inclusion of ground reaction forces (GRFs) in the dataset or not. Results identify ANNs as the best-performing predictor of KCFs, both in terms of Pearson R (0.89-0.98 for LeaveTrialsOut and 0.45-0.85 for LeaveSubjectsOut) and percentage normalized root mean square error (0.67-2.35 for LeaveTrialsOut and 1.6-5.39 for LeaveSubjectsOut). When GRFs were omitted from the dataset, no substantial decrease in prediction power of both models was observed. Our findings showcase the strength of ANNs to predict simultaneously multi-component KCF during walking at different speeds-even in the absence of GRFs-particularly applicable in real-time applications that make use of knee loading conditions to guide and treat patients.

Three-month efficacy of three knee braces in the treatment of medial knee osteoarthritis in a randomized crossover trial

Immediate biomechanical and functional effects of knee braces are often reported, however, the duration and type of knee brace treatment for knee osteoarthritis (KOA) remain unclear. The objective was to evaluate usage, comfort, pain, and knee adduction moment (KAM) of three knee braces each worn 3 months by patients. Twenty-four patients with KOA were assigned in a randomized crossover trial a valgus three-point bending system brace (V3P-brace), an unloader brace with valgus and external rotation functions (VER-brace) and a stabilizing brace used after ligament injuries (ACL-brace). Functional questionnaires and gait assessment were carried out before and after each brace wear period of 3 months. A Friedman test was applied between brace wear diary recordings. Repeated measures analyses of variance contrasted the factors brace type (ACL, V3P, and VER), time (pre and post) and wear (without and with) on comfort, pain, function, and KAM. Brace usage was similar, but the V3P-brace was slightly less worn. Discomfort was significantly lowered with the VER-brace. All knee braces relieved pain and symptoms from 10% to 40%. KAM angular impulse was reduced with the three braces, but the VER-brace obtained the lowest relative reduction of 9%. The interaction between time and wear indicated that part of the KAM reduction with brace wear was maintained post treatment. All three knee braces have great benefits for pain and function among the medial KOA population. The VER-brace offers additional advantages on daily use, comfort and KAM, which could improve compliance to brace treatment.

Computational comparison of different plating strategies in medial open-wedge high tibial osteotomy with lateral hinge fractures

Background

Lateral hinge fracture (LHF) is associated with nonunion and plate breakage in high tibial osteotomy (HTO). Mechanical studies investigating fixation strategies for LHFs to restore stability and avoid plate breakage are absent. This study used computer simulation to compare mechanical stabilities in HTO for different LHFs fixed with medial and bilateral locking plates.

Methods

A finite element knee model was created with HTO and three types of LHF, namely T1, T2, and T3 fractures, based on the Takeuchi classification. Either medial plating or bilateral plating was used to fix the HTO with LHFs. Furthermore, the significance of the locking screw at the combi hole (D-hole) of the medial TomoFix plate was evaluated.

Results

The osteotomy gap shortening distance increased from 0.53 to 0.76, 0.79, and 0.72 mm after T1, T2, and T3 LHFs, respectively, with medial plating only. Bilateral plating could efficiently restore stability and maintain the osteotomy gap. Furthermore, using the D-hole screw reduced the peak stress on the medial plate by 28.7% (from 495 to 353 MPa), 26.6% (from 470 to 345 MPa), and 32.6% (from 454 to 306 MPa) in T1, T2, and T3 LHFs, respectively.

Conclusion

Bilateral plating is a recommended strategy to restore HTO stability in LHFs. Furthermore, using a D-hole locking screw is strongly recommended to reduce the stress on the medial plate for lowering plate breakage risk.

Lower knee extensor and flexor strength is associated with varus thrust in people with knee osteoarthritis

Varus thrust during walking is common in people with knee osteoarthritis (OA) and can increase the risk of disease progression. Lower limb muscle strength, particularly isokinetic strength, may play a role in varus thrust. The purpose of this study was to investigate the relationships between varus thrust and isokinetic strength knee extensors and flexors in people with and without knee OA . Data from participants with (n = 28) and without (n = 68) knee OA were used. All participants underwent gait analysis during walking at a self-selected pace. Isokinetic knee extensor and flexor strength were measured at 60°/s and 120°/s. Varus thrust was measured using peak knee adduction velocity and knee adduction excursion during the first half of stance. Multiple linear regression was used to examine relationships between strength and varus thrust in the two groups separately while adjusting for age, sex, walking speed, and static alignment. In those with knee OA, knee extensor (Model R² = 27.0%) and flexor torque (Model R² = 28.5%) at 60°/s were negatively associated with peak adduction velocity. No other associations were seen between strength and varus thrust measures in the OA group. No associations were seen in the control group. Lower isokinetic knee extensor and flexor muscle at 60°/s strength is related to greater magnitude of varus thrust in individuals with knee OA but not in those without OA. Isokinetic strength deficits may be involved in varus thrust.

Biomechanical effects of screw orientation and plate profile on tibial condylar valgus osteotomy - Finite-element analysis

Tibial condylar valgus osteotomy (TCVO) is a type of open wedge high tibial osteotomy for correcting intra-articular deformities of medial knee osteoarthritis. However, there are no implant design and related biomechanical investigations specifically for TCVO. This study aims to investigate the effects of the proximal screw direction and plate profile on the biomechanical behaviors of the TCVO construct. Based on computed tomography images, the tibia model with TCVO was simulated. Four variations (straight and contoured plate profile × convergent and divergent proximal screw direction) with two loading conditions (compressive loads and torsional load) were compared by finite-element method. Fracture risk and construct stability were chosen as the comparison indices. For both loading conditions, the fracture risk of screw, plate and bone was the lowest in straight plate with divergent screw direction (SD), while contoured plate with convergent screw direction (CC) was the highest. Similar results were found in construct stability, SD allowed the smallest micromotions of the L-shaped opening gap, but CC allowed the highest. Divergent screw direction can decrease fracture risk of all components and provide better construct stability, while contoured plate profile seems like to have converse effects. If stability is the major concern, straight plate with divergent screw is recommended for patients with heavy load demands. Contoured plate may be suitable for skinny patients that can reduce the soft tissue irritation.

What is the impact of patellofemoral joint degeneration and malalignment on patient-reported outcomes after lateral unicompartmental knee arthroplasty?

Aims

It remains controversial whether patellofemoral joint pathology is a contraindication to lateral unicompartmental knee arthroplasty (UKA). This study aimed to evaluate the effect of preoperative radiological degenerative changes and alignment on patient-reported outcome scores (PROMs) after lateral UKA. Secondarily, the influence of lateral UKA on the alignment of the patellofemoral joint was studied.

Methods

A consecutive series of patients who underwent robotic arm-assisted fixed-bearing lateral UKA with at least two-year follow-up were retrospectively reviewed. Radiological evaluation was conducted to obtain a Kellgren Lawrence (KL) grade, an Altman score, and alignment measurements for each knee. Postoperative PROMs were assessed using the Kujala (Anterior Knee Pain Scale) score, Knee Injury and Osteoarthritis Outcome Score Joint Replacement (KOOS JR), and satisfaction levels.

Results

A total of 140 knees (130 patients) were identified for analysis. At mean 4.1 years (2.0 to 8.5) follow-up, good to excellent Kujala scores were reported. The presence of mild to moderate preoperative patellofemoral joint osteoarthritis had no impact on these scores (KL grade 0 vs 1 to 3, p = 0.203; grade 0 to 1 vs 2 to 3, p = 0.674). Comparable scores were reported by patients with osteoarthritis (Altman score of ≥ 2) evident on either the medial or lateral patellofemoral joint facet (medial, p = 0.600 and lateral, p = 0.950). Patients with abnormal patellar congruence and tilt angles (≥ 17° and ≥ 14°, respectively) reported good to excellent Kujala scores. Furthermore, lateral UKA resulted in improvements to patellofemoral alignment.

Conclusion

This is the first study demonstrating that mild to moderate preoperative radiological degenerative changes and malalignment of the patellofemoral joint are not associated with poor patient-reported outcomes at mid-term follow-up after lateral fixed-bearing UKA. Our data suggest that this may be explained by realignment of the patella and thereby redistribution of loads across the patellofemoral joint. Cite this article: Bone Joint J 2020;102-B(6):727–735.

Gender differences in the knee joint loadings during gait

BACKGROUND

The differences in anatomical structure between men and women are widely known. Unfortunately, the influence of gender on the biomechanics of a healthy knee joint during gait is still poorly understood.

RESEARCH QUESTION

The aim of the presented study was to determine loads acting in the knee joint during gait, based on the observation of a large group of healthy young adults, in particular to determine the influence of gender on values of forces and moments and their time characteristics during gait cycle.

METHODS

Time-spatial gait parameters and ground reaction force were registered for 86 persons (43 females and 43 males) using a motion capture system and force plates. The numerical simulation with the AnyBody system was used to estimate loadings acting in the knee joint. Differences between women and men were tested using the unpaired Student's t-test with a Bonferroni correction.

RESULTS

The maximum values of loadings acting in the knee joint were: 411.1 %BW (body weight) for resultant force, 390.6 %BW for proximo-distal force, 110.8 %BW for antero-posterior force, 77.0 %BW for medio-lateral force, 2.63 %BWh (body weight times height) for flexion/extension moment, 0.97 %BWh for internal/external rotation moment and 5.7 %BWh for abduction/adduction moment. In general, the normalised forces were greater in the male group, while the normalised external moments acting on the knee were greater in the female group. Local extrema of forces during the stance phase were observed earlier for women.

SIGNIFICANCE

Knowledge about gender differences in loadings acting in the knee joint can be of great importance in the case of detecting the early stages of gait abnormalities and treatment planning.

Using Cumulative Load to Explain How Body Mass Index and Daily Walking Relate to Worsening Knee Cartilage Damage Over Two Years: The MOST Study

OBJECTIVE

Knee cartilage damage is often linked to mechanical overloading. However, cartilage requires mechanical load to remain healthy, suggesting that underloading may be detrimental. This study was undertaken to examine knee overloading and underloading by defining cumulative load as the joint effects of body mass index (BMI) and daily walking, and examine the relationship between cumulative load and worsening cartilage damage over 2 years.

METHODS

We used data from the Multicenter Osteoarthritis Study. Steps/day, measured by accelerometry, and BMI were calculated at the 60-month visit. Cartilage damage on magnetic resonance imaging was semiquantitatively scored using the Whole-Organ Magnetic Resonance Imaging Score (WORMS) at the 60-month and 84-month visits; worsening damage was defined as increased WORMS between visits. Risk ratios (RRs) and 95% confidence intervals (95% CIs) were calculated using binomial regression, with adjustment for potential confounders.

RESULTS

Our study included 964 participants, 62% of whom were female, with a mean ± SD age of 66.9 ± 7.5 years. Participants had a mean ± SD BMI of 29.7 ± 4.8 kg/m² and walked a mean ± SD of 7,153 ± 2,591 steps/day. Participants who walked a moderate number of steps/day (6,000-7,900) or a high number of steps/day (>7,900) and had a high BMI (>31 kg/m² ) had a greater risk of worsening medial tibiofemoral (TF) damage (RR 2.83 [95% CI 1.46-5.48] and RR 2.61 [95% CI 1.50-4.54], respectively) compared with those who walked similar steps/day and had a low BMI (18-27 kg/m² ). Participants with a low number of steps/day (<6,000) and a low BMI had a greater risk of worsening medial TF and lateral patellofemoral (PF) damage (RR 2.03 [95% CI 1.06-3.92] and RR 2.28 [95% CI 1.06-4.85], respectively) compared with those who walked a high number of steps/day and had a low BMI. Effect estimates for other compartments of the knee did not reach statistical significance.

CONCLUSION

This study provides preliminary evidence that both overloading and underloading may be detrimental to medial TF cartilage, and underloading may be detrimental to lateral PF cartilage.

In vivo analysis of subchondral trabecular bone in patients with osteoarthritis of the knee using second-generation high-resolution peripheral quantitative computed tomography (HR-pQCT)

OBJECTIVE

Subchondral bone plays an important role in the pathological mechanisms of knee osteoarthritis (OA). High-resolution peripheral quantitative computed tomography (HR-pQCT) is an imaging modality allowing noninvasive microstructural analysis of human bone, and the second generation enables scanning of the knee. The purpose of this study was to perform in vivo analysis of subchondral trabecular bone in patients with medial knee OA, to elucidate features of bone microstructure in medial knee OA, and to investigate relationships between bone microstructure and both stage of disease and lower limb alignment.

METHODS

Subjects were 20 women, including both patients with medial knee OA (Kellgren-Lawrence (KL) grade 2, n = 5, KL grade 3, n = 7, and KL grade 4, n = 4; mean age: 63.0 years; body mass index (BMI): 23.8 kg/m²) and volunteers without knee OA (KL grade 1, n = 4, mean age: 66.0 years; BMI: 23.8 kg/m²). The proximal tibia (20-mm length) was scanned by second-generation HR-pQCT at a voxel size of 60.7 μm. A subchondral trabecular bone volume of 5 mm length was extracted from the medial and lateral plateaus. They were then divided into 4 regions: anterior, central, medial or lateral, and posterior. Finally, subchondral bone microstructure parameters were analyzed and compared, between each plateau and region. Relationships between microstructural parameters and disease stage (KL grade, minimum joint space width), and between those parameters and lower limb alignment (femorotibial angle: FTA, mechanical axis deviation: MAD) were also investigated.

RESULTS

In the medial plateau, volumetric bone mineral density (vBMD), bone volume fraction (BV/TV), and trabecular thickness were significantly higher and structure model index (SMI) was significantly lower than in the lateral plateau, particularly in the anterior, central, and medial regions (p < .01 each). In the anterior region of the medial plateau, vBMD, BV/TV, and connectivity density showed strong positive correlations with KL grade, FTA, and MAD (r-range: 0.61 to 0.83), while trabecular separation and SMI exhibited strong negative correlations with KL grade, FTA, and MAD (r-range: -0.60 to -0.83).

CONCLUSIONS

Higher bone volume, trabecular thickness, and a more plate-like structure were observed in the medial tibial plateau than in the lateral. Subchondral bone microstructure at the anterior region in the medial plateau showed strong relationships with KL grade and lower limb alignment. These results indicate that subchondral bone microstructure in this region may provide representative indices, particularly in medial knee OA. Although this study involved a specifically Asian cohort with a lower BMI distribution than other ethnic groups, the technique presented may be useful in studying the pathogenesis of OA or evaluating treatment effects.

Acute effect of partial body weight suspension on the level of cocontraction and gait biomechanics in women with knee osteoarthritis

Abstract Introduction: Knee osteoarthritis (OAK) is one of the most prevalent rheumatic diseases in the population, characterized by functional limitation and gait difficulties with profound clinical relevance, as walking is the most frequently performed daily activity. These functional limitations may be more pronounced when the disease is associated with obesity. Objective: To investigate the effect of different body weight suspension percentages on gait biomechanical variables and co-contraction percentages in women with OAK. Method: Fourteen women aged 50-75 years, with a body mass index between 26 and 35 and radiological diagnosis of OAK participated in the study. On the first day, anamnesis and familiarization with gait on the treadmill was performed. On the second day, treadmill gait assessment was performed using partial body weight support (SPPC) in three conditions-15%, 30%, and 45% suspension. During the evaluation, electromyographic and kinematic data were collected. The variables analyzed were percentage of hip (gluteus maximus/rectus femoris), knee (femoral biceps/vastus lateralis), and ankle (anterior tibial/lateral gastrocnemius), and length and step widths. A one-way analysis of variance was conducted, with a significance level of p < 0.05. Results: There was no significant difference in the length and step width and the level of co-contraction between the running conditions analyzed. Conclusion: Body weight suspension using SPPC during treadmill running did not alter the biomechanical variables of the gait of women with OAK.

Mid-term survivorship and patient-reported outcomes of robotic-arm assisted partial knee arthroplasty

Aims

Limited evidence is available on mid-term outcomes of robotic-arm assisted (RA) partial knee arthroplasty (PKA). Therefore, the purpose of this study was to evaluate mid-term survivorship, modes of failure, and patient-reported outcomes of RA PKA.

Methods

A retrospective review of patients who underwent RA PKA between June 2007 and August 2016 was performed. Patients received a fixed-bearing medial or lateral unicompartmental knee arthroplasty (UKA), patellofemoral arthroplasty (PFA), or bicompartmental knee arthroplasty (BiKA; PFA plus medial UKA). All patients completed a questionnaire regarding revision surgery, reoperations, and level of satisfaction. Knee Injury and Osteoarthritis Outcome Scores (KOOS) were assessed using the KOOS for Joint Replacement Junior survey.

Results

Mean follow-up was 4.7 years (2.0 to 10.8). Five-year survivorship of medial UKA (n = 802), lateral UKA (n = 171), and PFA/BiKA (n = 35/10) was 97.8%, 97.7%, and 93.3%, respectively. Component loosening and progression of osteoarthritis (OA) were the most common reasons for revision. Mean KOOS scores after medial UKA, lateral UKA, and PFA/BiKA were 84.3 (SD 15.9), 85.6 (SD 14.3), and 78.2 (SD 14.2), respectively. The vast majority of the patients reported high satisfaction levels after RA PKA. Subgroup analyses suggested tibial component design, body mass index (BMI), and age affects RA PKA outcomes. Five-year survivorship was 98.4% (95% confidence interval (CI) 97.2 to 99.5) for onlay medial UKA (n = 742) and 99.1% (95% CI 97.9 to 100) for onlay medial UKA in patients with a BMI < 30 kg/m2 (n = 479).

Conclusion

This large single-surgeon study showed high mid-term survivorship, satisfaction levels, and functional outcomes in RA UKA using metal-backed tibial onlay components. In addition, favourable results were reported in RA PFA and BiKA. Cite this article: Bone Joint J 2020;102-B(1):108–116

Investigation of Regression Methods for Reduction of Errors Caused by Bending of FSR-Based Pressure Sensing Systems Used for Prosthetic Applications

The pressure map at the interface of a prosthetic socket and a residual limb contains information that can be used in various prosthetic applications including prosthetic control and prosthetic fitting. The interface pressure is often obtained using force sensitive resistors (FSRs). However, as reported by multiple studies, accuracies of the FSR-based pressure sensing systems decrease when sensors are bent to be positioned on a limb. This study proposes the use of regression-based methods for sensor calibration to address this problem. A sensor matrix was placed in a pressure chamber as the pressure was increased and decreased in a cyclic manner. Sensors’ responses were assessed when the matrix was placed on a flat surface or on one of five curved surfaces with various curvatures. Three regression algorithms, namely linear regression (LR), general regression neural network (GRNN), and random forest (RF), were assessed. GRNN was selected due to its performance. Various error compensation methods using GRNN were investigated and compared to improve instability of sensors’ responses. All methods showed improvements in results compared to the baseline. Developing a different model for each of the curvatures yielded the best results. This study proved the feasibility of using regression-based error compensation methods to improve the accuracy of mapping sensor readings to pressure values. This can improve the overall accuracy of FSR-based sensory systems used in prosthetic applications.

Walking challenges in moderate knee osteoarthritis: A biomechanical and neuromuscular response to medial walkway surface translations

Sensations of knee instability are self-reported in 60-80% of individuals with knee osteoarthritis. These sensations are most often reported during walking; however, it remains unclear how they affect knee joint biomechanics and muscle activation patterns as indicators of joint function. Perturbation paradigms may provide insight into how the knee joint responds to walking challenges. Thus, the purpose of this study was to determine how individuals with moderate medial compartment knee osteoarthritis respond to unexpected, 3 cm medial walkway surface translations during gait compared to an asymptomatic control group. It is hypothesized that individuals with knee osteoarthritis will demonstrate altered biomechanics, and elevated and prolonged muscle activation compared to the asymptomatic group. Twenty asymptomatic individuals and 20 individuals with knee osteoarthritis walked on a dual-belt instrumented treadmill. Participants experienced 24 unexpected medial/lateral, 1 cm/3 cm walkway translations during mid-stance on each leg. Joint motions, moments and maximal voluntary isometric contraction amplitude normalized muscle activations were analyzed for the 3 cm walkway translations. Discrete measures were extracted from each biomechanical waveform and Principal Component Analysis (PCA) was used to determine knee joint muscle activation patterns. PCA is a factorization method to reduce dimensionality of EMG envelopes into linearly uncorrelated principal patterns (PP1, PP2, PP3) that explain the largest possible variance in the dataset. PP1 is often interpreted as a feature that explains the overall amplitude, while PP2 and PP3 are features that explain the variance in temporal activation patterns (i.e. how activation patterns change over the gait cycle). Statistical significance was determined using Analysis of Covariance models (alpha = 0.05). In response to the medial 3 cm walkway translation, increased activation amplitudes in the hamstring and gastrocnemius, captured by PP1 were found in both groups, as well as alterations in temporal activation patterns (captured by combinations of PP2 and PP3 patterns) across all muscle sites (p < 0.05). No group differences were demonstrated in joint motion and moment discrete metrics (p > 0.05) in response to the 3 cm translation. These findings suggest that the medial 3 cm walkway translation posed a challenged to knee function, however the biomechanical and neuromuscular response was similar between individuals with moderate knee osteoarthritis and asymptomatic individuals.

Patient-Specific Functional Analysis: The Key to the Next Revolution Towards the Treatment of Hip and Knee Osteoarthritis

Lower extremity joint arthroplasty surgery remains one of the most successful interventions in orthopaedics. While improvements in patient mobility and physical functioning following surgery are well-documented, there remains significant post-operative functional deficits in many patients. This highlights a need and an opportunity towards improving functional and patient-reported outcomes of arthroplasty surgery. This review summarizes key opportunities arising from the recent 2018 Orthopaedic Research Society Meeting in New Orleans, USA. In this review, the Canadian Orthopaedic Research Society (i.e., CORS) highlights key research advances, case examples, scientific messages, and personalized medical care approaches toward improving physical functioning in our knee and hip joint arthroplasty patients. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:1754-1759, 2019.

Patients With Medial Knee Osteoarthritis Reduce Medial Knee Contact Forces by Altering Trunk Kinematics, Progression Speed, and Stepping Strategy During Stair Ascent and Descent: A Pilot Study

Medial knee loading during stair negotiation in individuals with medial knee osteoarthritis, has only been reported in terms of joint moments, which may underestimate the knee loading. This study assessed knee contact forces (KCF) and contact pressures during different stair negotiation strategies. Motion analysis was performed in five individuals with medial knee osteoarthritis (52.8±11.0 years) and eight healthy subjects (51.0±13.4 years) while ascending and descending a staircase. KCF and contact pressures were calculated using a multi-body knee model while performing step-over-step at controlled and self-selected speed, and step-by-step strategies. At controlled speed, individuals with osteoarthritis showed decreased peak KCF during stair ascent but not during stair descent. Osteoarthritis patients showed higher trunk rotations in frontal and sagittal planes than controls. At lower self-selected speed, patients also presented reduced medial KCF during stair descent. While performing step-by-step, medial contact pressures decreased in osteoarthritis patients during stair descent. Osteoarthritis patients reduced their speed and increased trunk flexion and lean angles to reduce KCF during stair ascent. These trunk changes were less safe during stair descent where a reduced speed was more effective. Individuals should be recommended to use step-over-step during stair ascent and step-by-step during stair descent to reduce medial KCF.

Comparison of medial femoral cartilage deformation in normal adults according to gait conditions

This study aimed to explore the deformation of medial femoral cartilage in normal adults according to gait conditions. Overall, 76 normal adults without degenerative arthritis or a knee injury on medical history were randomly assigned into control, flatland walk, slope walk, and stepper walk groups. The control group was rested for 30 min, the test group performed flatland walking, 16° slope walking, and stepper walking, respectively. The thickness of medial femoral cartilage before and after gait was evaluated through ultrasound test. Compared with the control group, a significant difference was noted for medial femoral cartilage deformation before and after gait in all the three groups. Comparison of the medial femoral cartilage deformation among the groups revealed a significant difference between the control group and the flatland walk, slope walk, and stepper walk groups (P<0.05). The flatland walk group had a significant difference between the slope walk group and stepper walk group (P<0.05), whereas no significant difference was noted between the slope walk and stepper walk groups (P>0.05). After a 30-min walk, the thickness of medial femoral cartilage was reduced, and a difference in deformation was noted according to gait conditions. The thickness of medial femoral cartilage was reduced more in the stepper walk and slope walk groups, wherein more load operates on the knee, than the flatland walk group.

Combined enzymatic degradation of proteoglycans and collagen significantly alters intratissue strains in articular cartilage during cyclic compression

As degenerative joint diseases such as osteoarthritis (OA) progress, the matrix constituents, particularly collagen fibrils and proteoglycans, become damaged, therefore deteriorating the tissue's mechanical properties. This study aims to further the understanding of the effect of degradation of the different cartilage constituents on the mechanical loading environment in early stage OA. To this end, intact, collagen- and proteoglycan-depleted cartilage plugs were cyclically loaded in axial compression using an experimental model simulating in vivo cartilage-on-cartilage contact conditions in a micro-MRI scanner. Depletion of collagen and proteoglycans was achieved through enzymatic degradation with collagenase and chondroitinase ABC, respectively. Using a displacement-encoded imaging sequence (DENSE), strains were computed and compared in intact and degraded samples. The results revealed that, while degradation with one or the other enzyme had little effect on the contact strains, degradation with a combination of both enzymes caused an increase in the means and variance of the transverse, axial and shear strains, particularly in the superficial zone of the cartilage. This effect indicates that the balance between cartilage matrix constituents plays an essential role in maintaining the mechanical properties of the tissue, and a disturbance in this balance leads to a decrease of the load bearing capacity associated with degenerative joint diseases such as OA.

Detection of Early-Stage Degeneration in Human Articular Cartilage by Multiparametric MR Imaging Mapping of Tissue Functionality

To assess human articular cartilage tissue functionality by serial multiparametric quantitative MRI (qMRI) mapping as a function of histological degeneration. Forty-nine cartilage samples obtained during total knee replacement surgeries were placed in a standardized artificial knee joint within an MRI-compatible compressive loading device and imaged in situ and at three loading positions, i.e. unloaded, at 2.5 mm displacement (20% body weight [BW]) and at 5 mm displacement (110% BW). Using a clinical 3.0 T MRI system (Achieva, Philips), serial T1, T1ρ, T2 and T2* maps were generated for each sample and loading position. Histology (Mankin scoring) and biomechanics (Young’s modulus) served as references. Samples were dichotomized as intact (int, n = 27) or early degenerative (deg, n = 22) based on histology and analyzed using repeated-measures ANOVA and unpaired Student’s t-tests after log-transformation. For T1ρ, T2 and T2*, significant loading-induced differences were found in deg (in contrast to int) samples, while for T1 significant decreases in all zones were observed, irrespective of degeneration. In conclusion, cartilage functionality may be visualized using serial qMRI parameter mapping and the response-to-loading patterns are associated with histological degeneration. Hence, loading-induced changes in qMRI parameter maps provide promising surrogate parameters of tissue functionality and status in health and disease.

Biomechanical investigation of the type and configuration of screws used in high tibial osteotomy with titanium locking plate and screw fixation

Background

To maintain the corrected alignment after high tibial osteotomy (HTO), fixation with titanium locking plate and screws is widely used in current practice; however, screw breakage is a common complication. Thus, this study was to investigate the mechanical stability of HTO with locking plate and various screw fixations, including the length as well as the type.

Methods

A finite element (FE) model involving a distal femur, meniscus, and a proximal tibia with HTO fixed with a titanium locking plate and screws was created. The angle of the medial open wedge was 12°, and bone graft was not used. Two types of screws, namely conventional locking and far-cortical locking screws, with various lengths and configurations were used. At the proximal tibia, conventional locking screws with different lengths, 30 and 55 mm, were used; at the tibia shaft, different screw fixations including one-cortical, two-cortical, and far-cortical locking screws were used.

Results

The use of far-cortical locking screw generated the highest equivalent stress on the screws, which was four times (from 137.3 to 541 MPa) higher than that of the one-cortical screw. Also, it led to the maximum deformation of the tibia and a greater gap deformation at the osteotomy site, which was twice (from 0.222 to 0.442 mm) larger than that of the one-cortical screw. The effect of different locking screw length on tibia deformation and implant stress was minor.

Conclusion

Thus, far-cortical locking screws and plates increase interfragmentary movement but the screw stress is relatively high. Increasing the protection time (partial weight duration) is suggested to decrease the risk of screw breakage in HTO through fixation with titanium far-cortical locking screws and plates.

Biomechanical Alterations during Sit-to-Stand Transfer Are Caused by a Synergy between Knee Osteoarthritis and Obesity

Osteoarthritis is one of the major causes of immobility and its current prevalence in elderly (>60 years) is 18% in women and 9.6% in men. Patients with osteoarthritis display altered movement patterns to avoid pain and overcome movement limitations in activities of daily life, such as sit-to-stand transfers. Currently, there is a lack of evidence that distinguishes effects of knee osteoarthritis on sit-to-stand performance in patients with and without obesity. The purpose of this study was therefore to investigate differences in knee and hip kinetics during sit-to-stand movement between healthy controls and lean and obese knee osteoarthritis patients. Fifty-five subjects were included in this study, distributed over three groups: healthy controls (n=22), lean knee osteoarthritis (n=14), and obese knee OA patients (n=19). All subjects were instructed to perform sit-to-stand transfers at self-selected, comfortable speed. A three-dimensional movement analysis was performed to investigate compensatory mechanisms and knee and hip kinetics during sit-to-stand movement. No difference in sit-to-stand speed was found between lean knee OA patients and healthy controls. Obese knee osteoarthritis patients, however, have reduced hip and knee range of motion, which is associated with reduced peak hip and knee moments. Reduced vertical ground reaction force in terms of body weight and increased medial ground reaction forces indicates use of compensatory mechanisms to unload the affected knee in the obese knee osteoarthritis patients. We believe that an interplay between obesity and knee osteoarthritis leads to altered biomechanics during sit-to-stand movement, rather than knee osteoarthritis alone. From this perspective, obesity might be an important target to restore healthy sit-to-stand biomechanics in obese knee OA patients.

Stance and swing phase knee flexion recover at different rates following total knee arthroplasty: An inertial measurement unit study

Total knee arthroplasty (TKA) is the most common joint replacement in the United States. Range of motion (ROM) monitoring includes idealized clinic measures (e.g. goniometry during passive ROM) that may not accurately represent knee function. Accordingly, a novel, portable, inertial measurement unit (IMU) based ROM measurement method was developed, validated, and implemented. Knee flexion was computed via relative motion between two IMUs and validated via optical motion capture (p > 0.05). Prospective analyses of 10 healthy individuals (5M, 50 ± 19 years) and 20 patients undergoing TKA (3 lost to follow up, 10M, 65 ± 6 years) were completed. Controls wore IMUs for 1-week. Patients wore IMUs for 1-week pre-TKA, 6-weeks immediately post-TKA, and 1-week at 1-year post-TKA. Flexion was computed continuously each day (8-12 h). Metrics included daily maximum flexion and flexion during stance/swing phases of gait. Maximum flexion was equal between cohorts at all time points. Contrastingly, patient stance and swing flexion were reduced pre-TKA, yet improved post-TKA. Specifically, patient stance and swing flexion were reduced below control/pre-TKA values during post-TKA week 1. Stance flexion exceeded pre-TKA and equaled control levels after week 2. However, swing flexion only exceeded pre-TKA and equaled control levels at 1-year post-TKA. This novel method improves upon the accuracy/portability of current methods (e.g. goniometry). Interestingly, surgery did not impact maximum ROM, yet improved the ability to flex during gait allowing more efficient and safe ambulation. This is the first study continuously monitoring long-term flexion before/after TKA. The results offer richer information than clinical measures about expected TKA rehabilitation.

Tibiofemoral joint contact area and stress after single-bundle anterior cruciate ligament reconstruction with transtibial versus anteromedial portal drilling techniques

Background

During single-bundle ACLR, femoral tunnel location plays an important role in restoring the intact knee mechanisms, whereas malplacement of the tunnel was cited as the most common cause of knee instability. The objective of this study is to evaluate, objectively, the tibiofemoral contact area and stress after single-bundle (SB) anterior cruciate ligament reconstruction (ACLR) with femoral tunnel positions drilled by transtibial (TT) or anteromedial (AM) portal techniques.

Methods

Seven fresh human cadaveric knees underwent ACLR by the use of TT or AM portal techniques in a randomized order. These specimens were reused for ACL-R (TT and AM). The tibiofemoral contact area and stresses were gauged by an electronic stress-sensitive film inserted into the joint space. The knee was under the femoral axial compressive load of 1000 N using a biomechanics testing machine at 0°, 10°, 20°, and 30° of flexion. Three conditions were compared: (1) intact ACL, (2) ACLR by the use of the TT method, and (3) ACLR by the use of the AM portal method.

Results

Compared with AM portal ACL-reconstructed knees, a significantly decreased tibiofemoral contact area on the medial compartment was detected in the TT ACL-reconstructed knees at 20°of knee flexion (P = .047). Compared with the intact group, the TT ACLR group showed a higher mean stress at 20° and 30° of flexion on the medial compartments (P = .001, P = .003, respectively), while the AM portal ACLR group showed no significant differences at 30° of flexion (P = .073). The TT ACLR group also showed a higher mean maximum stress at 20° of flexion on the medial compartments (P = .047), while the AM portal ACLR group showed no significant differences at this angle(P = .319).

Discussion

The alternation of the tibiofemoral joint contact area and stress in reconstructed knees may be caused by the mismatch of the tibiofemoral joint during knee movement procedures compared with intact knees.

Conclusions

SB ACLR by the use of the AM portal method and TT method both alter the tibiofemoral contact area and stress when compared with the intact knee. When compared with the TT technique, ACLR by the AM portal technique more closely restores the intact tibiofemoral contact area and stress at low flexion angles.

Wearable Movement Sensors for Rehabilitation: A Focused Review of Technological and Clinical Advances

Recent technologic advancements have enabled the creation of portable, low-cost, and unobtrusive sensors with tremendous potential to alter the clinical practice of rehabilitation. The application of wearable sensors to track movement has emerged as a promising paradigm to enhance the care provided to patients with neurologic or musculoskeletal conditions. These sensors enable quantification of motor behavior across disparate patient populations and emerging research shows their potential for identifying motor biomarkers, differentiating between restitution and compensation motor recovery mechanisms, remote monitoring, telerehabilitation, and robotics. Moreover, the big data recorded across these applications serve as a pathway to personalized and precision medicine. This article presents state-of-the-art and next-generation wearable movement sensors, ranging from inertial measurement units to soft sensors. An overview of clinical applications is presented across a wide spectrum of conditions that have potential to benefit from wearable sensors, including stroke, movement disorders, knee osteoarthritis, and running injuries. Complementary applications enabled by next-generation sensors that will enable point-of-care monitoring of neural activity and muscle dynamics during movement also are discussed.

Association of malalignment, muscular dysfunction, proprioception, laxity and abnormal joint loading with tibiofemoral knee osteoarthritis - a systematic review and meta-analysis

Background

To investigate (1) the association of specific biomechanical factors with knee osteoarthritis and knee osteoarthritis development, and (2) the impact of other relevant risk factors on this association.

Methods

MEDLINE, EMBASE, CINAHL and SPORTDiscus were searched up until April 2017. Studies were included if they fulfilled the following criteria: the study 1) assessed the association of a biomechanical factor with knee osteoarthritis, or knee osteoarthritis development; 2) reported on skeletal malalignment, muscular dysfunction, impaired proprioception, laxity and abnormal loading during gait; 3) was a cohort study with participants developing knee osteoarthritis and participants not developing knee osteoarthritis, or a case-control or cross-sectional study with participants with knee osteoarthritis and without knee osteoarthritis. Risk of bias was assessed with the QUIPS tool and meta-analyses were performed using random effects models.

Results

Of 6413 unique studies identified, 59 cross-sectional studies were eligible for meta-analyses (9825 participants, 5328 with knee osteoarthritis). No cohort studies fulfilled the inclusion criteria. Compared with healthy controls, patients with knee osteoarthritis have higher odds of having lower muscle strength, proprioception deficits, more medial varus-valgus laxity and less lateral varus-valgus laxity. Patients with medial knee osteoarthritis have higher odds of having a higher knee adduction moment than healthy controls. Level of evidence was graded as ‘very low’ to ‘moderate’ quality. Due to large between study differences moderation of other risk factors on biomechanical risk factors could not be evaluated.

Conclusions

Patients with knee osteoarthritis are more likely to display a number of biomechanical characteristics. The causal relationship between specific biomechanical factors and the development of knee osteoarthritis could not be determined as no longitudinal studies were included. There is an urgent need for high quality, longitudinal studies to evaluate the impact of specific biomechanical factors on the development of knee osteoarthritis.

Trial Registration

(PROSPERO ID: CRD42015025092).

Electronic supplementary material

The online version of this article (10.1186/s12891-018-2202-8) contains supplementary material, which is available to authorized users.

Radiographic Changes in Nonoperative Contralateral Knee After Unilateral Total Knee Arthroplasty

BACKGROUND

Some patients perceive symptomatic improvement in the contralateral knee after unilateral total knee arthroplasty (TKA). This so-called "splinting effect" has been observed but has not been radiographically evaluated.

METHODS

A retrospective review of patients with bilateral knee osteoarthritis treated with unilateral TKA was performed. Patients were subcategorized into 2 groups based on whether contralateral TKA was performed within the 2-year period. Contralateral radiographic measurements were performed.

RESULTS

Forty-four of 203 patients had contralateral TKA performed within 2 years. Preoperative parameters were significantly worse in the bilateral group. By 6 weeks postoperatively, mechanical axis plumbline improved approximately 1°, with more change in those patients with preoperative varus alignment. Larger delta changes were also present in bilateral group preoperative to 1-year radiographs for tibiofemoral angle and joint space widening.

CONCLUSION

In patients with bilateral knee osteoarthritis who undergo unilateral TKA, a splinting effect may be present and measurable radiographically with improvement of contralateral mechanical axis plumbline. Further research is necessary to determine whether this improvement may delay contralateral TKA implantation.

Comparison of Gait Biomechanics in Patients with and without Knee Osteoarthritis during Different Phases of Gait

Background

This study aimed to characterise knee adduction angles (KAA) and knee adduction moments (KAM) and compare this with foot centre of pressure (COP) in volunteers with and without knee osteoarthritis (OA).

Methods

A total of 108 participants were recruited; 84 had no known pathology, 18 had medial knee OA, and six had lateral knee OA. Linear regression was used to determine correlations between the normalised COP, KAM, and KAA during each phase of gait for all participants.

Results

The first phase of gait demonstrated significant differences between groups for all measures: KAA in all phases, COP in phases one and two, and KAM in phase one only.

Conclusion

The largest mechanical changes are seen in the first phase of gait in osteoarthritic patients. Although COP is an easy to measure tool, it is not as sensitive as KAA and did not demonstrate a significant difference between healthy and medial OA patients.

Research methodology for orthopaedic surgeons, with a focus on outcome

Since improving the patient's condition is the ultimate goal of clinical care and research, this review of research methodology focuses on outcomes in the musculoskeletal field.This paper provides an overview of conceptual models, different types of outcomes and commonly assessed outcomes in orthopaedics as well as epidemiological and statistical aspects of outcomes determination, measurement and interpretation.Clinicians should determine the outcome(s) most important to patients and/or public health in collaboration with the patients, epidemiologists/statisticians and other stakeholders.Key points in outcome choice are to evaluate both the benefit and harm of a health intervention, and to consider short- and longer-term outcomes including patient-reported outcomes.Outcome estimation should aim at identifying a clinically important difference (not the same as a statistically significant difference), at presenting measures of effects with confidence intervals and at taking the necessary steps to minimize bias. Cite this article: EFORT Open Rev 2018;3 DOI: 10.1302/2058-5241.3.170064.

The effect of ageing and osteoarthritis on the mechanical properties of cartilage and bone in the human knee joint

Osteoarthritis is traditionally associated with cartilage degeneration although is now widely accepted as a whole-joint disease affecting the entire osteochondral unit; however site-specific cartilage and bone material properties during healthy ageing and disease are absent limiting our understanding. Cadaveric specimens (n = 12; 31–88 years) with grades 0–4 osteoarthritis, were dissected and spatially correlated cartilage, subchondral and trabecular bone samples (n = 8 per cadaver) were harvested from femoral and tibial localities. Nanoindentation was utilised to obtain cartilage shear modulus (G′) and bone elastic modulus (E). Cartilage G′ is strongly correlated to age (p = 0.003) and osteoarthritis grade (p = 0.007). Subchondral bone E is moderately correlated to age (p = 0.072) and strongly correlated to osteoarthritis grade (p = 0.013). Trabecular bone E showed no correlation to age (p = 0.372) or osteoarthritis grade (p = 0.778). Changes to cartilage G′ was significantly correlated to changes in subchondral bone E (p = 0.007). Results showed preferential medial osteoarthritis development and moderate correlations between cartilage G′ and sample location (p = 0.083). Also demonstrated for the first time was significant correlations between site-matched cartilage and subchondral bone material property changes during progressive ageing and osteoarthritis, supporting the role of bone in disease initiation and progression. This clinically relevant data indicates a causative link with osteoarthritis and medial habitual loading.

High occurrence of osteoarthritic histopathological features unaccounted for by traditional scoring systems in lateral femoral condyles from total knee arthroplasty patients with varus alignment

Background and purpose - A better understanding of the patterns and variation in initiation and progression of osteoarthritis (OA) in the knee may influence the design of therapies to prevent or slow disease progression. By studying cartilage from the human lateral femoral condyle (LFC), we aimed to: (1) assess specimen distribution into early, mild, moderate, and severe OA as per the established histopathological scoring systems (HHGS and OARSI); and (2) evaluate whether these 2 scoring systems provide sufficient tools for characterizing all the features and variation in patterns of OA. Patients and methods - 2 LFC osteochondral specimens (4 x 4 x 8 mm) were collected from 50 patients with idiopathic OA varus knee and radiographically preserved lateral compartment joint space undergoing total knee arthroplasty. These were fixed, sectioned, and stained with HE and Safranin O-Fast Green (SafO). Results - The histopathological OA severity distribution of the 100 specimens was: 6 early, 62 mild, 30 moderate, and 2 severe. Overall, 45/100 specimens were successfully scored by both HHGS and OARSI: 12 displayed low OA score and 33 displayed cartilage surface changes associated with other histopathological features. However, 55/100 samples exhibited low surface structure scores, but were deemed to be inadequately scored by HHGS and OARSI because of anomalous features in the deeper zones not accounted for by these systems: 27 exhibited both SafO and tidemark abnormal features, 16 exhibited only SafO abnormal features, and 12 exhibited tidemark abnormal features. Interpretation - LFC specimens were scored as mild to moderate OA by HHGS and OARSI. Yet, several specimens exhibited deep zone anomalies while maintaining good surface structure, inconsistent with mild OA. Overall, a better classification of these anomalous histopathological features could help better understand idiopathic OA and potentially recognize different subgroups of disease.

Kinematic features in patients with lateral discoid meniscus injury during walking

At present, there few studies on the kinematic features of lateral discoid meniscus injury. In this study, a motion capture system was used to investigate the motion characteristics of knees with lateral discoid meniscus after injury, and the differences between the knees with lateral meniscus and intact knees were compared. Fourteen patients diagnosed with unilateral lateral discoid meniscus injury, fourteen patients diagnosed with unilateral lateral meniscus injury, and fourteen normal subjects with healthy knees were recruited and grouped. Through kinematic gait analysis, it was found that the subjects in the two groups with meniscus injuries exhibited significantly smaller ranges of rotation and translation than those with healthy knees on the sagittal, coronal, and horizontal planes, but not in proximal-distal translation. Maximum lateral tibial translation and maximum internal tibial rotation in the knees with lateral discoid meniscus injury were significantly decreased compared to those with lateral meniscus injury. The results show that the kinematic features of knees with lateral discoid meniscus injury are statistically different than those of healthy knees and knees with lateral meniscus injury. This study provides an important reference for the dynamic function of knees with lateral discoid meniscus injury.

Reduction of frontal plane knee load caused by lateral trunk lean depends on step width

The internal knee abduction moment (KAM) in osteoarthritis is reduced by increased lateral trunk lean (TL). Mechanistically, this occurs as the Centre of Mass (COM) moves further over the stance leg. Since the size of the base of support constrains the COM, an associated increase in step width (SW) would be expected to maintain stability. This study tested the effects of TL on SW and KAM in healthy participants (n = 21) who performed normal and 6° TL walks. The latter was controlled via audio-visual biofeedback. We found two distinct gait strategies in TL walk: widening the step width substantially (>50%) to permit an increase in the COM displacement (WSW, n = 13), or maintaining a baseline SW and minimally displacing the COM by moving the hip/pelvic complex in the opposite direction (NSW, n = 8). WSW doubled SW (11.3 ± 2.4 v. 24.7 ± 5.5 cm, p < .0001), NSW did not change SW (12.2 ± 2.8 v. 13.7 ± 4.7 cm, p > .05). These two distinct gait strategies resulted in unique patterns of KAM reduction across the stance phase. NSW reduced KAM impulse significantly in the initial half (0.08 ± 0.02 v. 0.06 ± 0.02, p = .04) but not in the later stance phase (0.07 ± 0.02 v. 0.07 ± 0.04, p > .05). WSW reduced KAM significantly in both initial (0.11 ± 0.03 v. 0.08 ± 0.04, p < .001) and later stance phase (0.09 ± 0.02 v. 0.06 ± 0.03, p < .001). KAM peak results followed the pattern of impulse. This study has revealed two distinct mechanisms for increasing lateral trunk lean which can be used to explain discrepancies in past research and in the future could be used to individualise gait re-training strategies.

Effects of sex and obesity on gait biomechanics before and six months after total knee arthroplasty: A longitudinal cohort study

BACKGROUND

Gait biomechanics, sex, and obesity can contribute to suboptimal outcomes from primary total knee arthroplasty. The aims of this study were to i) determine if sex and/or obesity influence the amount of change in gait biomechanics from pre-surgery to six months post-surgery and; ii) assess if gait returns to normal in men and women.

METHODS

Three-dimensional gait analysis was performed on 43 patients undergoing primary total knee arthroplasty for knee osteoarthritis (pre- and six months post-operative) and 40 asymptomatic controls. Mixed linear regression models were fit to assess which factors influenced change in gait biomechanics within the arthroplasty cohort, and interaction terms were included to assess if biomechanics returned to normal following surgery.

FINDINGS

Male peak knee adduction moment (p < 0.001) and impulse (p < 0.001) decreased six months following arthroplasty, whilst gait in women remained unchanged after surgery. Obesity did not influence gait changes in men or women. Gait of female arthroplasty participants did not differ from female controls after surgery except for sagittal plane knee range of motion (p = 0.003), whilst men differed from controls for peak knee adduction moment (p = 0.011), knee range of motion (p < 0.001), and peak knee flexion moment (p < 0.001).

INTERPRETATION

Sex, but not obesity, influenced changes in gait biomechanics after arthroplasty. Men retained abnormal gait patterns after surgery, whilst women did not. Further research should determine the long-term implications of gait abnormalities seen in men after arthroplasty.

Knee medial and lateral contact forces in a musculoskeletal model with subject-specific contact point trajectories

Contact point (CP) trajectory is a crucial parameter in estimating medial/lateral tibio-femoral contact forces from the musculoskeletal (MSK) models. The objective of the present study was to develop a method to incorporate the subject-specific CP trajectories into the MSK model. Ten healthy subjects performed 45 s treadmill gait trials. The subject-specific CP trajectories were constructed on the tibia and femur as a function of extension-flexion using low-dose bi-plane X-ray images during a quasi-static squat. At each extension-flexion position, the tibia and femur CPs were superimposed in the three directions on the medial side, and in the anterior-posterior and proximal-distal directions on the lateral side to form the five kinematic constraints of the knee joint. The Lagrange multipliers associated to these constraints directly yielded the medial/lateral contact forces. The results from the personalized CP trajectory model were compared against the linear CP trajectory and sphere-on-plane CP trajectory models which were adapted from the commonly used MSK models. Changing the CP trajectory had a remarkable impact on the knee kinematics and changed the medial and lateral contact forces by 1.03 BW and 0.65 BW respectively, in certain subjects. The direction and magnitude of the medial/lateral contact force were highly variable among the subjects and the medial-lateral shift of the CPs alone could not determine the increase/decrease pattern of the contact forces. The suggested kinematic constraints are adaptable to the CP trajectories derived from a variety of joint models and those experimentally measured from the 3D imaging techniques.