Patellofemoral Contact Force Research Articles

The influence of different walking strategies on patellofemoral and tibiofemoral contact forces in individuals with patellofemoral instability

The influence of different walking strategies on patellofemoral and tibiofemoral contact forces in individuals with patellofemoral instability

Patella height influences patellofemoral contact and kinematics following cruciate-retaining total knee replacement.

The role of patella height is discussed controversially in total knee arthroplasty (TKA). Therefore, this computational study aims to systematically analyze the biomechanical effect of different patella heights on patellofemoral (PF) forces and kinematics after cruciate-retaining (CR) TKA. We implemented a CR bicondylar TKA with a dome patellar button in a validated dynamic musculoskeletal multibody model of a male human knee joint. Retropatellar dynamics (contact force [N], shear force [N], patellar shift [mm], tilt [°], and rotation [°]) were evaluated during dual-limb squat motion (flexion from 0° to 90°) with simulated active muscle forces and the effects of different patella heights (Blackburne-Peel [BP] ratio of 0.39, 0.49, 0.65, 0.85, 1.01, and 1.1 were systematically examined). As active knee flexion increased, PF contact force also increased. Patella alta (BP = 1.1) resulted in higher PF contact forces compared to normal patella height (BP = 0.65) by up to 16%. Contrarily, patella baja was associated with decreased PF forces by 7%. Compared to patella baja (BP = 0.39), patella alta (BP = 1.1) considerably increased the contact force by up to 25%. Different patellar heights mainly affected PF shear forces during early knee flexion. Concerning PF kinematics, patella alta (BP = 1.1) yielded a greater lateral tilt of more than 4° and higher patellar rotation by up to 3° during deep knee flexion, compared to normal patella height (BP = 0.65). Our computational study indicates that patella alta is associated with the highest PF contact and shear force after the implantation of a CR bicondylar TKA. This should be considered in PF disorders following TKA.

Tibial sagittal and rotational alignment reduce patellofemoral stresses in posterior stabilized total knee arthroplasty

Patellofemoral joint complications remain an important issue in total knee arthroplasty. We compared the patellofemoral contact status between cruciate-retaining and posterior-stabilized designs with varying degrees of tibial sagittal and rotational alignment using a computer simulation to ensure proper alignments in total knee arthroplasty. Knee kinematics, patellofemoral contact force and quadriceps force were computed using a musculoskeletal modeling program (LifeMOD/KneeSIM 2010; LifeModeler, Inc., San Clemente, California) during a weight-bearing deep knee bend. Two different posterior tibial slope (PTS)s (3° and 7°) and five different tibial tray rotational alignments (neutral, internal 5° and 10°, and external 5° and 10°) were simulated. Patellofemoral contact area and stresses were next computed using finite element analysis. The patellofemoral contact force for the posterior-stabilized design was substantially lower than the cruciate-retaining design after post-cam contact because of increasing femoral roll-back. Neutral rotational alignment of the tibial component resulted in smaller differences in patellofemoral contact stresses between cruciate-retaining and posterior-stabilized designs for PTSs of 3° or 7°. However, the patellar contact stresses in the cruciate-retaining design were greater than those in posterior-stabilized design at 120° of knee flexion with PTS of 3° combined with internal rotation of the tibial component. Our study provides biomechanical evidence implicating lower PTSs combined with internal malrotation of the tibial component and the resultant increase in patellofemoral stresses as a potential source of anterior knee pain in cruciate-retaining design.

Techniques to determine knee joint contact forces during squatting: A systematic review.

This review article provides an overview of techniques used to determine human knee joint contact forces during squatting. The main two approaches are experimental and theoretical. Thigh calf contact has a significant effect on knee forces and should not be neglected. In this study, data were searched electronically and organized by techniques to find knee joint contact force during squatting theoretically and experimentally. There was a large variation in peak tibiofemoral (CV = 0.45) and patellofemoral (CV = 0.38) contact forces predicted theoretically. However, very little variation was observed between peak tibiofemoral contact forces (CV = 0.12) measured in vivo experimentally but measured knee joint force is available up to a limited knee flexion angle. There was a reduction in knee joint contact forces due to thigh calf contact. Literature of knee joint contact force prediction theoretically during squatting incorporating thigh calf contact force is very limited.

Effects of the Anterolateral Ligament and Anterior Cruciate Ligament on Knee Joint Mechanics: A Biomechanical Study Using Computational Modeling.

Background:Recent studies on lateral knee anatomy have reported the presence of a true ligament structure, the anterolateral ligament (ALL), in the anterolateral region of the knee joint. However, its biomechanical effects have not been fully elucidated.Purpose:To investigate, by using computer simulation, the association between the ALL and anterior cruciate ligament (ACL) under dynamic loading conditions.Study Design:Descriptive laboratory study; Level of evidence, 5.Methods:The authors combined medical imaging from 5 healthy participants with motion capture to create participant-specific knee models that simulated the entire 12 degrees of freedom of tibiofemoral (TF) and patellofemoral (PF) joint behaviors. These dynamic computational models were validated using electromyographic data, muscle activation data, and data from previous experimental studies. Forces exerted on the ALL with ACL deficiency and on the ACL with ALL deficiency, as well as TF and PF contact forces with deficiencies of the ACL, ALL, and the entire ligament structure, were evaluated under gait and squat loading. A single gait cycle and squat cycle were divided into 11 time points (periods 0.0-1.0). Simulated ligament forces and contact forces were compared using nonparametric repeated-measures Friedman tests.Results:Force exerted on the ALL significantly increased with ACL deficiency under both gait- and squat-loading conditions. With ACL deficiency, the mean force on the ALL increased by 129.7% under gait loading in the 0.4 period (P < .05) and increased by 189% under high flexion during the entire cycle of squat loading (P < .05). A similar trend of significantly increased force on the ACL was observed with ALL deficiency. Contact forces on the TF and PF joints with deficiencies of the ACL, ALL, and entire ligament structure showed a complicated pattern. However, contact force exerted on TF and PF joints with respect to deficiencies of ACL and ALL significantly increased under both gait- and squat-loading conditions.Conclusion:The results of this computer simulation study indicate that the ACL and the ALL of the lateral knee joint act as secondary stabilizers to each other under dynamic load conditions.

Patellofemoral contact forces after ACL reconstruction: A longitudinal study

Osteoarthritis (OA) development after ACL reconstruction (ACLR) is common. Patellofemoral OA after ACLR is as prevalent as tibiofemoral OA; however, few have explored the mechanisms leading to disease development in this compartment. Biomechanical alterations may be one mechanism responsible for post-traumatic knee OA. Patellofemoral contact forces during dynamic tasks, such as running and single leg hops, have been assessed at return to sport and later time points. The results of these studies, however, contradict each other, are only cross-sectional in nature, and are limited to specific points in time within the movement pattern. The purpose of this study was to assess patellofemoral contact forces 3, 6, and 24 months after ACLR during level walking over the entirety of the movement pattern. Patellofemoral contact forces were calculated after determination of muscle forces from a validated, subject-specific, EMG-driven neuromusculoskeletal model. Statistical parametric mapping was used to compare patellofemoral contact forces between limbs and across time points. Patellofemoral underloading of the involved limb (vs. uninvolved) was present at 3 months (p < 0.001 from 7 to 30% of stance) and 6 months (p = 0.001 from 11 to 23% of stance and p = 0.025 from 27 to 32%) after ACLR but was resolved by 24 months. Both limbs’ load increased from 3 to 6 months. The involved limb displayed relatively consistent loads from 6 months onward, while the uninvolved limb’s decreased back down towards their 3-month values. Overall, these results suggest that early patellofemoral underloading exists after ACLR and may be leading to patellofemoral OA development.

Effects of Forefoot Shoe on Knee and Ankle Loading during Running in Male Recreational Runners

Objectives: Although overuse running injury risks for the ankle and knee are high, the effect of different shoe designs on Achilles tendon force (ATF) and Patellofemoral joint contact force (PTF) loading rates are unclear. Therefore, the primary objective of this study was to compare the ATF at the ankle and the PTF and Patellofemoral joint stress force (PP) at the knee using different running shoe designs (forefoot shoes vs. normal shoes). Methods: Fourteen healthy recreational male runners were recruited to run over a force plate under two shoe conditions (forefoot shoes vs. normal shoes). Sagittal plane ankle and knee kinematics and ground reaction forces were simultaneously recorded. Ankle joint mechanics (ankle joint angle, velocity, moment and power) and the ATF were calculated. Knee joint mechanics (knee joint angle velocity, moment and power) and the PTF and PP were also calculated. Results: No significant differences were observed in the PTF, ankle plantarflexion angle, ankle dorsiflexion power, peak vertical active force, contact time and PTF between the two shoe conditions. Compared to wearing normal shoes, wearing the forefoot shoes demonstrated that the ankle dorsiflexion angle, knee flexion velocity, ankle dorsiflexion moment extension, knee extension moment, knee extension power, knee flexion power and the peak patellofemoral contact stress were significantly reduced. However, the ankle dorsiflexion velocity, ankle plantarflexion velocity, ankle plantarflexion moment and Achilles tendons force increased significantly. Conclusions: These findings suggest that wearing forefoot shoes significantly decreases the patellofemoral joint stress by reducing the moment of knee extension, however the shoes increased the ankle plantarflexion moment and ATF force. The forefoot shoes effectively reduced the load on the patellofemoral joint during the stance phase of running. However, it is not recommended for new and novice runners and patients with Achilles tendon injuries to wear forefoot shoes.

Underloading, not overloading, of the patellofemoral joint increases the risk of early osteoarthritis after ACL reconstruction

Background: Approximately 50% of adolescents and young adults who rupture their anterior cruciate ligament (ACL) develop osteoarthritis within 10 years. While most reports of osteoarthritis after ACL injury focus on the tibiofemoral joint, patellofemoral osteoarthritis is common and strongly associated with symptoms and impaired function. The mechanisms underpinning the development of patellofemoral osteoarthritis after ACL injury are unknown but may relate to altered joint loading. This study aimed to determine if altered patellofemoral loading is associated with the presence and/or worsening of early patellofemoral osteoarthritis following ACL reconstruction (ACLR). Methods: Forty-six participants (30 men, age 27±5 years, BMI 24.5±3.1 kg.m-2) were randomly selected from a cohort of 111 consecutively recruited patients with primary hamstring-tendon ACLR and completed magnetic resonance imaging (MRI) and biomechanics testing of their index knee 1-year post-ACLR. Biomechanics testing involved recording trunk and lower-limb movement with a 12-camera 3D motion analysis system and ground reaction force data during the landing phase of a standardised forward hop. These data were input into a musculoskeletal model to calculate patellofemoral joint contact forces normalised to body weight. Follow-up MRI was completed on 32 participants 5-years post-ACLR. Early patellofemoral osteoarthritis was defined as the presence of a patellofemoral cartilage lesion by an experienced musculoskeletal radiologist. Generalised linear models (Poisson) assessed the relationship between patellofemoral joint loading and prevalent early patellofemoral osteoarthritis at 1-year and worsening patellofemoral osteoarthritis between 1- and 5-years adjusting for sex and age. Results: At 1-year following ACLR, 14 (30%) participants had early patellofemoral osteoarthritis. Those with a lower peak patellofemoral joint contact force were more likely to have early patellofemoral osteoarthritis (prevalence ratio: 1.37, 95%CI 1.02-1.85). Of the 32 participants with 5-year follow-up data, 9 (28%) displayed worsening patellofemoral osteoarthritis. A lower peak patellofemoral joint contact force at 1-year increased the risk of worsening patellofemoral osteoarthritis (risk ratio: 1.54, 95%CI 1.13-2.11). Discussion: Young adults following ACLR who underload their patellofemoral joint during a hopping task are at high risk of early patellofemoral osteoarthritis onset and progression within the first 5-years after ACLR. For every one unit (i.e., body weight) decrease in peak patellofemoral joint contact force, the risk of incident or progressive early patellofemoral osteoarthritis increases ~50%. These findings challenge traditional thinking that joint overloading drives post-traumatic osteoarthritis and provides new targets for osteoarthritis prevention. Conflict of interest statement: My co-authors and I acknowledge that we have no conflict of interest of relevance to this abstract.

Dysplastic Patellofemoral Joints Lead to a Shift in Contact Forces: A 3D-Printed Cadaveric Model

Background: The distribution of contact forces across the dysplastic patellofemoral joint has not been adequately quantified because models cannot easily mimic the dysplasia of both the trochlea and the patella. Thus, the mechanical consequences of surgical treatments to correct dysplasia cannot be established. Purpose/Hypothesis: The objective of this study was to quantify the contact mechanics and kinematics of normal, mild, and severely dysplastic patellofemoral joints using synthetic mimics of the articulating surfaces on cadavers. We tested the hypothesis that severely dysplastic joints would result in significantly increased patellofemoral contact forces and abnormal kinematics. Study Design: Controlled laboratory study. Method: Patellofemoral dysplasia was simulated in 9 cadaveric knees by replacing the native patellar and trochlear surfaces with synthetic patellar and trochlear implants. For each knee, 3 synthetic surface geometries (normal, showing no signs of dysplasia; mild, exemplifying Dejour type A; and severe, exemplifying Dejour type B) were randomized for implantation and testing. Patellar kinematics and the sum of forces acting on the medial and lateral patellar facets were computed for each knee and for each condition at 10° increments from 0° to 70° of flexion. Results: A pronounced lateral shift in the weighted center of contact of the lateral facet occurred for severely dysplastic knees from 20° to 70° of flexion. Compared with normal geometries, lateral patellar facet forces exhibited a significant increase only with mild dysplasia from 50° to 70° of flexion and with severe dysplasia at 70° of flexion. No measurable differences in medial patellar facet mechanics or joint kinematics occurred. Conclusion: Our hypothesis was rejected: Severely dysplastic joints did not result in significantly increased patellofemoral contact forces and abnormal kinematics in our cadaveric simulation. Rather, severe dysplasia resulted in a pronounced lateral shift in contact forces across the lateral patellar facet, while changes in kinematics and the magnitude of contact forces were not significant. Clinical Relevance: Including dysplasia of both the patella and trochlea is required to fully capture the mechanics of this complex joint. The pronounced lateralization of contact force in severely dysplastic patellofemoral joints should be considered to avoid cartilage overload with surgical manipulation.

Modern femoral component design in total knee arthroplasty shows a lower patellar contact force during knee flexion compared with its predecessor

BackgroundThe relationship between the femoral component design in total knee arthroplasty (TKA) and the patellofemoral contact force, as well as the soft tissue balance, has not been well reported thus far. MethodsTwenty-eight mobile-bearing posterior-stabilized (PS) TKAs using the traditional model (PFC Sigma) and 27 mobile-bearing PS TKAs using the latest model (Attune) were included. Surgeries were performed using the measured resection technique assisted with the computed tomography (CT)-based free-hand navigation system. After all the trial components were placed, patellar contact forces on the medial and lateral sides were measured using two uniaxial ultrathin force transducers with the knee at 0°, 10°, 30°, 60°, 90°, 120°, and 135° of flexion. The joint component gap and the varus ligament balance of the femorotibial joint were also measured. The non-paired Student’s t-test was conducted to compare the values of the two groups. ResultsThe medial patellar contact force was significantly lower for Attune group than for PFC Sigma group at 120° of knee flexion (P = 0.0058). The lateral patellar contact force was also significantly lower for Attune group than PFC Sigma group at 120° and 135° of knee flexion (P = 0.0068 and P = 0.036). The joint component gap, as well as the varus ligament balance, showed no statistically significant difference between the two groups. ConclusionsReduced thickness and width of the anterior flange of the femoral component in the Attune may play a role in low patellar contact force.

Knee biomechanics during squat rising with patella alta and after distal transfer of tibial tubercular surgery

Patella alta has commonly seen in prior adolescent cerebral palsy population with crouch gait pattern. Unfortunately, for the treatments of PA and crouch gait, the outcomes of physical therapy, orthotic and surgical treatments are highly questionable. The purpose of this study is to investigate the effects of patella alta on knee biomechanics and to analyze the benefits of distal transfer of tibial tubercule (DTTT) during dual limb knee squat extension. A three-dimensional dynamic knee model comprising patellofemoral and tibiofemoral joints was developed. Patellar tendon length was increased 25% and 50% of its original length to simulate the patology. Tibiofemoral and patellofemoral contact forces, loads on ligament bundles, tibial rotations and quadriceps efficiencies were compared for patology, normal and after DTTT surgery (DTTTS). The results showed that patella alta, increases the tibiofemoral and patellofemoral compressive force, alters the neutral tension of ligament bundles, reduces the medio-lateral knee stability and increases the efficiency of the quadriceps muscle during squat rising. Even though DTTTS normalized some of the biomechanical alterations, internal rotation in higher flexion angles, valgus-varus rotation of the tibia and the tension of aACL and PCL remained different than normal. These alterations may play a contributory role to develop cartilage degeneration on tibiofemoral and patellofermoral joints. Inadequate quadriceps force and abnormal loading pattern on some of the ligaments may also contribute to the recurrence mechanism of crouch gait after DTTTS surgery.

Load Distribution at the Patellofemoral Joint During Walking.

We combined computational modelling with experimental gait data to describe and explain load distribution across the medial and lateral facets of the patella during normal walking. The body was modelled as a 13-segment, 32-degree-of-freedom (DOF) skeleton actuated by 80 muscles. The knee was represented as a 3-body, 12-DOF mechanical system with deformable articular cartilage surfaces at the tibiofemoral (TF) and patellofemoral (PF) joints. Passive responses of the knee model to 100 N anterior-posterior drawer and 5 Nm axial torque tests were consistent with cadaver data reported in the literature. Trajectories of 6-DOF TF and PF joint motion and articular joint contact calculated for walking were also consistent with measurements obtained from biplane X-ray imaging. The force acting on the lateral patellar facet was considerably higher than that on the medial facet throughout the gait cycle. The vastus medialis, vastus lateralis and patellar tendon forces contributed substantially to the first peak in the PF contact force during stance whereas all three portions of the vasti and rectus femoris were responsible for the second peak during swing. A higher lateral patellar contact force was caused mainly by the laterally-directed shear force applied by the quadriceps muscles, especially the vastus lateralis, intermedius and rectus femoris. A better understanding of the contributions of the individual knee muscles to load distribution in the PF compartment may lead to improved surgical and physiotherapy methods to treat PF disorders.

Musculoskeletal Multibody Simulation Analysis on the Impact of Patellar Component Design and Positioning on Joint Dynamics after Unconstrained Total Knee Arthroplasty.

Patellofemoral (PF) disorders are considered a major clinical complication after total knee replacement (TKR). Malpositioning and design of the patellar component impacts knee joint dynamics, implant fixation and wear propagation. However, only a limited number of studies have addressed the biomechanical impact of the patellar component on PF dynamics and their results have been discussed controversially. To address these issues, we implemented a musculoskeletal multibody simulation (MMBS) study for the systematical analysis of the patellar component’s thickness and positioning on PF contact forces and kinematics during dynamic squat motion with virtually implanted unconstrained cruciate-retaining (CR)-TKR. The patellar button thickness clearly increased the contact forces in the PF joint (up to 27%). Similarly, the PF contact forces were affected by superior–inferior positioning (up to 16%) and mediolateral positioning (up to 8%) of the patellar button. PF kinematics was mostly affected by the mediolateral positioning and the thickness of the patellar component. A medialization of 3 mm caused a lateral patellar shift by up to 2.7 mm and lateral patellar tilt by up to 1.6°. However, deviations in the rotational positioning of the patellar button had minor effects on PF dynamics. Aiming at an optimal intraoperative patellar component alignment, the orthopedic surgeon should pay close attention to the patellar component thickness in combination with its mediolateral and superior–inferior positioning on the retropatellar surface. Our generated MMBS model provides systematic and reproducible insight into the effects of patellar component positioning and design on PF dynamics and has the potential to serve as a preoperative analysis tool.

Patellofemoral joint contact forces at different activities - effects of modeling assumptions

Purpose: Osteoarthritis (OA) at the knee most commonly begins at the patellofemoral (PF) joint. A dominant theory of OA aetiology is that mechanical overloading disrupts the physiological remodeling processes (homeostasis) of the cartilage, to eventually result in its breakdown, causing severe pain and disability. Besides reduced PF contact area it is increased load(i.e. the PF joint contact force = PFJCF) that increases cartilage stress. Neither stress, nor the PFJCF can be measured directly, but can be estimated from the force in the patellar tendon, as a resultant of the force in the quadriceps.

Immediate Effects of Medially Posted Insoles on Lower Limb Joint Contact Forces in Adult Acquired Flatfoot: A Pilot Study.

Flatfoot is linked to secondary lower limb joint problems, such as patellofemoral pain. This study aimed to investigate the influence of medial posting insoles on the joint mechanics of the lower extremity in adults with flatfoot. Gait analysis was performed on fifteen young adults with flatfoot under two conditions: walking with shoes and foot orthoses (WSFO), and walking with shoes (WS) in random order. The data collected by a vicon system were used to drive the musculoskeletal model to estimate the hip, patellofemoral, ankle, medial and lateral tibiofemoral joint contact forces. The joint contact forces in WSFO and WS conditions were compared. Compared to the WS group, the second peak patellofemoral contact force (p < 0.05) and the peak ankle contact force (p < 0.05) were significantly lower in the WSFO group by 10.2% and 6.8%, respectively. The foot orthosis significantly reduced the peak ankle eversion angle (p < 0.05) and ankle eversion moment (p < 0.05); however, the peak knee adduction moment increased (p < 0.05). The reduction in the patellofemoral joint force and ankle contact force could potentially inhibit flatfoot-induced lower limb joint problems, despite a greater knee adduction moment.

A greater reduction in the distal femoral anterior condyle improves flexion after total knee arthroplasty in patients with osteoarthritis

BackgroundThe effect of an anterior condylar height (ACH) change after total knee arthroplasty (TKA) is not well-known. The effect of an ACH change was evaluated on postoperative knee flexion, New Knee Society Scores (2011KSS), and patellofemoral contact force. MethodsThe study included 101 knees that underwent TKA. The medial or lateral ACH was measured using pre-operative and postoperative computed tomography. Pearson correlation between the change in ACH and knee flexion was calculated. The determinant of the change in flexion was evaluated using multivariable linear regression. The association between ACH and 2011KSS was assessed. Using the cases with the three highest and three lowest pre-operative medial ACHs, computer simulation was performed to detect the changes in patellofemoral contact forces. ResultsA postoperative reduction in ACH correlated with increased flexion at one year (medial ACH, R = 0.58; lateral ACH, R = 0.48). On multivariable linear regression, reductions in medial ACH (β = 1.7, P < 0.001) and pre-operative flexion (β = −0.3, P < 0.001) were associated with increased flexion. A decrease in ACH was associated with improvements in advanced activities (medial, R2 = 0.06; lateral, R2 = 0.08) in 2011KSS. On computer simulation, all three cases with reduced and increased medial ACHs showed decreased and increased patellofemoral contact forces, respectively. ConclusionsA change in ACH was an independent predictor of knee flexion after TKA. Greater reduction in ACH was associated with improved flexion after TKA, whereas an increase in postoperative ACH may be a risk factor for flexion loss.

Patellofemoral Joint Loads during Running Immediately Changed by Shoes with Different Minimalist Indices: A Cross-sectional Study

Purpose: Given the high incidence of patellofemoral pain syndrome (PFPS) in runners, this study aimed to investigate the immediate effect of shoes with different minimalist indices (MI) on the mechanical loads of the patellofemoral joint. Methods: Fifteen healthy male rearfoot strike runners were recruited to complete overground running trials at 3.33 m/s (±5%) in two running shoe conditions (MI = 26% versus MI = 86%). The amount of ten Vicon infrared cameras (100 Hz) and two Kistler force plates (1000 Hz) were used to collect kinematic and ground reaction force (GRF) data simultaneously. Quadriceps strength, patellofemoral contact force, patellofemoral contact area, and patellofemoral contact stress were calculated. Results: No significant differences were observed in the impact force and the second peak of the vertical GRF between the two shoe conditions. Compared to wearing low-MI shoes, wearing high-MI shoes showed that the maximum flexion angle of the knee, the contact area of patellofemoral joint and the peak knee extension moment reduced significantly (p &lt; 0.01), and the peak patellofemoral contact force and stress decreased significantly (p &lt; 0.05). Conclusion: These findings suggest that wearing high-MI shoes significantly decreases the patellofemoral contact force and patellofemoral joint stress by reducing the moment of knee extension, thus effectively reducing the load of the patellofemoral joint during the stance phase of running and potentially lowering the risk of PFPS.

Biomechanical modeling of deep squatting: Effects of the interface contact between posterior thigh and shank

Epidemiological studies indicate that occupational activities that require extended deep knee flexion or kneeling are associated with a higher prevalence of knee osteoarthritis. In many sport activities, such as a catcher in a baseball or a softball game, athletes have to make repetitive deep squatting motions, which have been associated with the development of osteochondritis dissecans. Excessive deep knee flexion postures may cause excessive loading in the knee joint. In deep knee flexion postures, the posterior aspect of the shank will contact the posterior thigh, resulting in a compressive force within the soft tissues. The current study was aimed at analyzing the effects of the posterior thigh/shank contact on the joint loading during deep knee flexion in a natural knee. An existing, whole body model with detailed anatomical components of the knee (AnyBody) has been adopted and modified for this study. The effects of the posterior thigh/shank contact were evaluated by comparing the results of the inverse dynamic analysis for two scenarios: with and without the posterior thigh/shank contact force. Our results showed that, in a deep squatting posture (knee flexion 120+ degrees), the posterior thigh/shank contact helps reduce the patellofemoral (PF) and tibiofemoral (TF) normal contact forces by 42% and 57%, respectively.

Influence of Variation in Sagittal Placement of the Femoral Component after Cruciate-Retaining Total Knee Arthroplasty.

Prosthetic alignment is an important factor for long-term survival in cruciate-retaining (CR) total knee arthroplasty (TKA). The purpose of this study is to investigate the influence of sagittal placement of the femoral component on tibiofemoral (TF) kinematics and kinetics in CR-TKA. Five sagittal placements of femoral component models with -3, 0, 3, 5, and 7 degrees of flexion are developed. The TF joint kinematics, quadriceps force, patellofemoral contact force, and posterior cruciate ligament force are evaluated using the models under deep knee-bend loading. The kinematics of posterior TF translation is found to occur with the increase in femoral-component flexion. The quadriceps force and patellofemoral contact force decrease with the femoral-component flexion increase. In addition, extension of the femoral component increases with the increase in posterior cruciate ligament force. The flexed femoral component in CR-TKA provides a positive biomechanical effect compared with a neutral position. Slight flexion could be an effective alternative technique to enable positive biomechanical effects with TKA prostheses.

The effects of pediatric obesity on patellofemoral joint contact force during walking

BackgroundObesity increases a child’s risk of developing knee pain across the lifespan, potentially through elevated patellofemoral joint loads that occur during habitual weight-bearing activities. Research questionDo obese children have greater absolute and patellar-area-normalized patellofemoral joint forces compared to healthy weight children during walking? MethodsWe utilized a cross-sectional design to address the aims of this study. Experimental biomechanics data were collected during treadmill walking in 10 healthy-weight and 10 obese 8–12 year-olds. We used radiographic images to develop subject-specific musculoskeletal models, generated walking simulations from the experimental data, and predicted patellofemoral joint contact force using established techniques. ResultsWe found that the obese children had 1.98 times greater absolute (p = 0.002) and 1.81 times greater patellar-area-normalized (p = 0.008) patellofemoral joint contact forces compared to the healthy-weight children. We observed a stronger relationship between absolute patellofemoral joint contact force and BMI (r2=0.58) than between patellofemoral joint contact force and body fat percentage (r2=0.38). SignificanceOur results indicate that obese children walk with increased patellofemoral loads in absolute terms and also relative to the area of the articulating surfaces, which likely contributes to the increased risk of knee pain in this pediatric population. This information, which provides a baseline comparison for future longitudinal studies, also informs the type and frequency of physical activity prescription aimed at reducing the risk of knee injury and improving long-term outcomes.