Do Interlimb Knee Joint Loading Asymmetries Persist throughout Stance during Uphill Walking Following Total Knee Arthroplasty?

The purpose of this study was to determine differences in total (TCF), medial compartment (MCF), and lateral compartment (LCF) tibiofemoral joint compressive forces and related muscle forces between replaced and non-replaced limbs during level and uphill walking at an incline of 10°. A musculoskeletal modeling and simulation approach using static optimization was used to determine the muscle forces and TCF, MCF, and LCF for 25 patients with primary TKA. A statistical parametric mapping repeated-measures ANOVA was conducted on knee compressive forces and muscle forces using statistical parametric mapping. Greater TCF, MCF, and LCF values were observed throughout the loading response, mid-stance, and late stance during uphill walking. During level walking, knee extensor muscle forces were greater throughout the first 50% of the stance during level walking, yet greater during uphill walking during the last 50% of the stance. Conversely, knee flexor muscle forces were greater through the loading response and push-off phases of the stance. No between-limb differences were observed for compressive or muscle forces, suggesting that uphill walking may promote a more balanced loading of replaced and non-replaced limbs. Additionally, patients with TKA appear to rely on the hamstrings muscle group during the late stance for knee joint control, thus supporting uphill walking as an effective exercise modality to improve posterior chain muscle strength.

Radiographic Measures for the Assessment of Frontal and Sagittal Knee Alignments and the Associated Normality Values: A Meta-Analysis

Objective

The purpose of this literature review was to identify knee alignment assessment methods using radiography in the sagittal and frontal planes and to identify normality values for classifying knee alignment using these methods.

Methods

A systematic review with a meta-analysis was conducted. The eligibility criterion was studies that performed radiographic examinations to assess the knee alignment of adults without a history of hip or knee prosthesis surgery. The methodological qualities of the included studies were assessed using the QUADAS-2 tool. A meta-analysis was performed to measure the normality values of knee alignment in the frontal plane.

Results

The hip-knee-ankle (HKA) angle was the measure most frequently used to assess knee alignment. Only a meta-analysis of HKA normality values was possible. Thereby, we found normality values of the HKA angle for the overall population, men, and women. The normality values of knee alignment for healthy adults that were found in this study were as follows: overall sample (male and female patients) HKA angle = -0.2° (-2.8° to 2.41°), male patient HKA angle = 0.77° (-2.91° to 7.94°), and female patient HKA angle = -0.67° (-5.32° to 3.98°).

Conclusion

This review identified the most common methods and expected values for knee alignment assessment methods using radiography in the sagittal and frontal planes. We suggest HKA angles ranging from -3° to 3° as the cutoff for classifying knee alignment in the frontal plane, in accordance with the normality limits found in the meta-analysis.

Tibiofemoral compressive force during downhill walking in patients with primary total knee arthroplasty: A statistical parametric mapping approach

BACKGROUND

Downhill walking is a necessary part of daily life and an effective activity in post-operative rehabilitation following total knee arthroplasty. The purpose of this study was to determine differences in the behavior of total, medial, and lateral tibiofemoral compressive forces as well as knee extensor and flexor muscle forces between different limbs of patients with total knee arthroplasty (replaced, non-replaced) during downhill and level walking.

METHODS

Musculoskeletal modeling and simulation were implemented to determine muscle forces and tibiofemoral compressive forces in 25 patients with total knee arthroplasty. A 2 × 2 [Limb (replaced, non-replaced) × Slope (0°, 10°)] Statistical parametric mapping repeated measures analysis of variance was conducted on selected variables.

FINDINGS

Statistical parametric mapping did not identify any between-limb differences for compressive or muscle forces. Differences in joint compressive and muscle forces persisted throughout different intervals of stance-phase between level and downhill walking. Knee extensor muscle forces were distinctly greater during level walking for nearly all of stance phase. Knee flexor muscle force was greater during downhill walking for >60% of stance. Statistical parametric mapping did identify regions of significance between level and downhill walking that coincided temporally (near loading response and push off) with peak joint moment and joint compressive forces traditionally reported using discrete variable analyses.

INTERPRETATION

Downhill walking may be a safe and useful rehabilitation tool for post-knee arthroplasty rehabilitation that will not disproportionally load either the replaced or the non-replaced joint and where the quadriceps muscles can be strengthened during a gait-specific task.

Computational biomechanics of human knee joint in stair ascent: Muscle-ligament-contact forces and comparison with level walking

About a third of knee joint disorders originate from the patellofemoral (PF) site that makes stair ascent a difficult activity for patients. A detailed finite element model of the knee joint is coupled to a lower extremity musculoskeletal model to simulate the stance phase of stair ascent. It is driven by the mean of measurements on the hip-knee-ankle moments-angles as well as ground reaction forces reported in healthy individuals. Predicted muscle activities compare well to the recorded electromyography data. Peak forces in quadriceps (3.87 BW, body weight, at 20% instance in our 607 N subject), medial hamstrings (0.77 BW at 20%), and gastrocnemii (1.21 BW at 80%) are estimated. Due to much greater flexion angles-moments in the first half of stance, large PF contact forces (peak of 3.1 BW at 20% stance) and stresses (peak of 4.83 MPa at 20% stance) are estimated that exceed their peaks in level walking by fourfold and twofold, respectively. Compared with level walking, ACL forces diminish in the first half of stance but substantially increase later in the second half (peak of 0.76 BW at 75% stance). Under nearly similar contact forces at 20% of stance, the contact stress on the tibiofemoral (TF) medial plateau reaches a peak (9.68 MPa) twice that on the PF joint suggesting the vulnerability of both joints. Compared with walking, stair ascent increases peak ACL force and both peak TF and PF contact stresses. Reductions in the knee flexion moment and/or angle appear as a viable strategy to mitigate internal loads and pain.

The effect of hip abductor fatigue on knee kinematics and kinetics during normal gait

Objective

To investigate the effect of hip abductor fatigue on the kinematics and kinetics of the knee joint during walking in healthy people to provide a new approach for the prevention and treatment of knee-related injuries and diseases.

Methods

Twenty healthy participants, ten females, and ten males, with a mean age of 25.10 ± 1.2 years, were recruited. Isometric muscle strength testing equipment was used to measure the changes in muscle strength before and after fatigue, and the surface electromyography (SEMG) data during fatigue were recorded synchronously. The Vicon system and an AMTI© force platform were used to record the kinematic parameters and ground reaction force (GRF) of twenty participants walking at a self-selected speed before and after fatigue. Visual 3D software was used to calculate the angles and torques of the hip and knee joints.

Results

After fatigue, the muscle strength, median frequency (MF) and mean frequency (MNF) of participants decreased significantly (P < 0.001). The sagittal plane range of motion (ROM) of the knee (P < 0.0001) and hip joint (P < 0.01) on the fatigue side was significantly smaller than before fatigue. After fatigue, the first and second peaks of the external knee adduction moment (EKAM) in participants were greater than before fatigue (P < 0.0001), and the peak values of the knee abduction moment were also higher than those before fatigue (P < 0.05). On the horizontal plane, there is also a larger peak of internal moment during walking after fatigue (P < 0.01).

Conclusion

Hip abductor fatigue affects knee kinematics and kinetics during normal gait. Therefore, evaluating hip abductor strength and providing intensive training for patients with muscle weakness may be an important part of preventing knee-related injuries.

A subject-specific musculoskeletal model to predict the tibiofemoral contact forces during daily living activities

Accurate prediction of tibiofemoral contact force (TFCF) during daily living activities is significant for understanding the initiation, progression, and treatment of knee osteoarthritis (KOA). However, the diversity of target activities, prediction accuracy, and computational efficiency of the current musculoskeletal simulations need to be further improved. In this study, a subject-specific musculoskeletal model considered the tibiofemoral alignment, medial-lateral contact locations, secondary tibiofemoral and all patellofemoral motions, and knee ligaments was proposed to predict the TFCFs during the five daily activities (normal walking, sit-to-stand, stand-to-sit, stair ascent, and stair descent) in OpenSim software. The standing lower-limbs-full-length radiograph, local radiograph of knee joint, motion capture data, and force plate data of eighteen subjects were acquired as the input data of the musculoskeletal model. The results showed good agreements of TFCFs between the predictions based on our proposed musculoskeletal model and the in-vivo measurements based on instrumented knee implants during the five daily activities (RMSE: 0.16 ∼ 0.31 BW, R²: 0.88 ∼ 0.97, M: -0.11 ∼ -0.02, P: 0.03 ∼ 0.10, and C: 0.04 ∼ 0.14). Additionally, the order of the peak total and lateral TFCFs from low to high was normal walking, stair ascent and stand-to-sit, and stair descent and sit-to-stand (P < 0.05), and the peak medial TFCF was stand-to-sit, sit-to-stand, normal walking, stair ascent and stair descent (P < 0.05). The outcomes of this study are valuable for further understanding the knee biomechanics during daily living activities and providing theoretical guidance for the treatments of KOA.

Increased Q-factor increases medial compartment knee joint contact force during cycling

As Q-Factor (QF: inter-pedal distance) is increased, the internal knee abduction moment (KAbM) also increases, however it is unknown if this increased KAbM is associated with increased medial compartment knee joint contact force in cycling. In the absence of in vivo measurement, musculoskeletal modeling simulations may provide a viable option for estimating knee joint contact forces in cycling. The primary purpose of this study was to investigate the effect of increasing QF on knee joint total (TCF), and medial (MCF) compartment contact force during ergometer cycling. The secondary purpose was to evaluate whether KAbM and knee extension moment are accurate predictors of MCF in cycling. Musculoskeletal simulations were performed to estimate TCF and MCF for sixteen participants cycling at an original QF (150 mm), and wide QF (276 mm), at 80 W and 80 rotations per minute. Paired samples t-tests were used to detect differences between QF conditions. MCF increased significantly, however, TCF did not change at wide QF. Peak knee extensor muscle force did not change at wide QF. Peak knee flexor muscle force was significantly reduced with wide QF. Regression analyses showed KAbM and knee extension moments explained 87.4% of the variance in MCF when considered alongside QF. The increase of MCF may be attributed to increased frontal-plane pedal reaction force moment arm. Future research may seek to implement QF modulation as a part of rehabilitation or training procedures utilizing cycling in cases where medial compartment joint loading is of importance.

Modified vector coding analysis of trunk and lower extremity kinematics during maximum and sub-maximum back squats

The back squat is a complex movement with significant demands on the lower extremities and trunk to raise an external load. The back squat is simultaneously an open and closed kinetic chain movement that requires coordination of the entire body for successful completion of the lift. Therefore, this study aimed to examine coordination of the thigh and shank, trunk and thigh, and the hip and knee during the concentric phase of maximum, supra-maximum (at 105% max), and sub-maximum (at 80% max) back squats. Fourteen resistance trained adults participated in this study. Maximum back squat loads were determined using a previously determined progressive load protocol. Motion capture of the trunk and lower extremities and ground reaction force data were recorded during all squats. Angle-angle plots and modified vector coding were performed to analyze segment and joint coupling angles and knee-hip moments. Overall, the concentric phase of back squats depict a transition from early knee dominance to hip dominance as the system ascends. Interestingly, all squats presented with coupling of thigh-rising and trunk-falling. Based on the angle-angle plots and the modified vector coding results, the prolonged coupling of trunk falling and thigh rising likely resulted in too large of a moment arm for the external load for the participants to overcome during Supramax conditions.

Predicting Knee Joint Instability Using a Tibio-Femoral Statistical Shape Model

Statistical shape models (SSMs) are a well established computational technique to represent the morphological variability spread in a set of matching surfaces by means of compact descriptive quantities, traditionally called "modes of variation" (MoVs). SSMs of bony surfaces have been proposed in biomechanics and orthopedic clinics to investigate the relation between bone shape and joint biomechanics. In this work, an SSM of the tibio-femoral joint has been developed to elucidate the relation between MoVs and bone angular deformities causing knee instability. The SSM was built using 99 bony shapes (distal femur and proximal tibia surfaces obtained from segmented CT scans) of osteoarthritic patients. Hip-knee-ankle (HKA) angle, femoral varus-valgus (FVV) angle, internal-external femoral rotation (IER), tibial varus-valgus (TVV) angles, and tibial slope (TS) were available across the patient set. Discriminant analysis (DA) and logistic regression (LR) classifiers were adopted to underline specific MoVs accounting for knee instability. First, it was found that thirty-four MoVs were enough to describe 95% of the shape variability in the dataset. The most relevant MoVs were the one encoding the height of the femoral and tibial shafts (MoV #2) and the one representing variations of the axial section of the femoral shaft and its bending in the frontal plane (MoV #5). Second, using quadratic DA, the sensitivity results of the classification were very accurate, being all >0.85 (HKA: 0.96, FVV: 0.99, IER: 0.88, TVV: 1, TS: 0.87). The results of the LR classifier were mostly in agreement with DA, confirming statistical significance for MoV #2 (p = 0.02) in correspondence to IER and MoV #5 in correspondence to HKA (p = 0.0001), FVV (p = 0.001), and TS (p = 0.02). We can argue that the SSM successfully identified specific MoVs encoding ranges of alignment variability between distal femur and proximal tibia. This discloses the opportunity to use the SSM to predict potential misalignment in the knee for a new patient by processing the bone shapes, removing the need for measuring clinical landmarks as the rotation centers and mechanical axes.

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.