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Christopher M. Powers - One of the best experts on this subject based on the ideXlab platform.

  • Changes in Patellofemoral pain resulting from repetitive impact landings are associated with the magnitude and rate of Patellofemoral Joint loading.
    Clinical biomechanics (Bristol Avon), 2018
    Co-Authors: Lee T. Atkins, C. Roger James, Hyung Suk Yang, Phillip S. Sizer, Jean-michel Brismée, Steven F. Sawyer, Christopher M. Powers
    Abstract:

    Abstract Background Although a relationship between elevated Patellofemoral forces and pain has been proposed, it is unknown which Joint loading variable (magnitude, rate) is best associated with pain changes. The purpose of this study was to examine associations among Patellofemoral Joint loading variables and changes in Patellofemoral pain across repeated single limb landings. Methods Thirty-one females (age: 23.5(2.8) year; height: 166.8(5.8) cm; mass: 59.6(8.1) kg) with PFP performed 5 landing trials from 0.25 m. The dependent variable was rate of change in pain obtained from self-reported pain scores following each trial. Independent variables included 5-trial averages of peak, time-integral, and average and maximum development rates of the Patellofemoral Joint reaction force obtained using a previously described model. Pearson correlation coefficients were calculated to evaluate individual associations between rate of change in pain and each independent variable (α = 0.05). Stepwise linear multiple regression (αenter = 0.05; αexit = 0.10) was used to identify the best predictor of rate of change in pain. Findings Subjects reported an average increase of 0.38 pain points with each landing trial. Although, rate of change in pain was positively correlated with peak force (r = 0.44, p = 0.01), and average (r = 0.41, p = 0.02) and maximum force development rates (r = 0.39, p = 0.03), only the peak force entered the predictive model explaining 19% of variance in rate of change in pain (r2 = 0.19, p = 0.01). Interpretation Peak Patellofemoral Joint reaction force was the best predictor of the rate of change in pain following repetitive singe limb landings. The current study supports the theory that Patellofemoral Joint loading contributes to changes in Patellofemoral pain.

  • Sagittal Plane Trunk Posture Influences Patellofemoral Joint Stress During Running
    Journal of Orthopaedic & Sports Physical Therapy, 2014
    Co-Authors: Hsiang-ling Teng, Christopher M. Powers
    Abstract:

    Study Design Cross-sectional, repeated-measures. Objectives To examine the association between sagittal plane trunk posture and Patellofemoral Joint (PFJ) stress, and to determine whether modifying sagittal plane trunk posture influences PFJ stress during running. Background Patellofemoral pain is the most common injury among runners and is thought to be the result of elevated PFJ stress. While sagittal plane trunk posture has been shown to influence tibiofemoral Joint mechanics, no study has examined the influence of trunk posture on PFJ kinetics. Methods Twenty-four asymptomatic recreational runners (12 women, 12 men) ran overground at a speed of 3.4 m/s under 3 trunk-posture conditions: self-selected, flexed, and extended. Trunk and knee kinematics, ground reaction forces, and electromyographic signals from selected lower extremity muscles were obtained. A previously described PFJ biomechanical model was used to quantify PFJ stress. Results The mean ± SD trunk flexion angles under the self-selected, fl...

  • Patellofemoral Joint stress during weight bearing and non weight bearing quadriceps exercises
    Journal of Orthopaedic & Sports Physical Therapy, 2014
    Co-Authors: Christopher M. Powers, Richard B Souza, Yujen Chen, Kaiyu Ho, Shawn Farrokhi
    Abstract:

    Study Design Single-group, repeated-measures design. Objective To compare Patellofemoral Joint (PFJ) stress among weight-bearing and non-weight-bearing quadriceps exercises. Background An important consideration when prescribing exercises to strengthen the quadriceps in persons with Patellofemoral pain is to minimize PFJ loading. Currently, there is disagreement in the literature as to which exercises and ranges of motion best accomplish this goal. Methods Ten healthy subjects participated. Lower extremity kinematics, kinetics, and electromyography of the knee musculature were obtained during a weight-bearing squatting exercise and 2 non-weight-bearing knee extension exercises: (1) knee extension with variable resistance, and (2) knee extension with constant resistance. A previously described biomechanical model was used to estimate PFJ stress at 0°, 15°, 30°, 45°, 60°, 75°, and 90° of knee flexion. PFJ stress was compared among the 3 exercises using a 2-way analysis of variance with repeated measures. Re...

  • The influence of heel height on Patellofemoral Joint kinetics during walking.
    Gait & posture, 2012
    Co-Authors: Mark G. Blanchette, Christopher M. Powers
    Abstract:

    Although wearing high-heeled shoes has long been considered a risk factor for the development for Patellofemoral pain (PFP) in women, Patellofemoral Joint kinetics during high-heeled gait has not been examined. The purpose of this study was to determine if heel height increases Patellofemoral Joint loading during walking. Eleven healthy women (mean age 25.0±3.1 yrs) participated. Lower extremity kinematics and kinetics were obtained under 3 different shoe conditions: low heel (1.27 cm), medium heel (6.35 cm), and high heel (9.53 cm). Patellofemoral Joint stress was estimated using a previously described biomechanical model. Model outputs included Patellofemoral Joint reaction force, Patellofemoral Joint stress and utilized contact area as a function of the gait cycle. One-way ANOVAs with repeated measures were used to compare the model outputs and knee Joint angles among the 3 shoe conditions. Peak Patellofemoral Joint stress was found to increase significantly (p=0.002) with increasing heel height (low heel: 1.9±0.7 MPa, medium heel: 2.6±1.2 MPa, and high heel: 3.6±1.5 MPa). The increased Patellofemoral Joint stress was mainly driven by an increase in Joint reaction force owing to higher knee extensor moments and knee flexion angles. Our findings support the premise that wearing high-heeled shoes may be a contributing factor with respect to the development of PFP.

  • Patellofemoral Joint forces and stress during forward step up lateral step up and forward step down exercises
    Journal of Orthopaedic & Sports Physical Therapy, 2011
    Co-Authors: Chatchada Chinkulprasert, Roongtiwa Vachalathiti, Christopher M. Powers
    Abstract:

    Study Design Controlled laboratory study using a repeated-measures design. Objective To quantify Patellofemoral Joint reaction force (PFJRF) and stress (PFJS) during forward step-up (FSU), lateral step-up (LSU), and forward step-down (FSD) exercises. Background Although FSU, LSU, and FSD exercises are commonly used in Patellofemoral Joint rehabilitation programs, the influence of these stepping tasks on Patellofemoral Joint kinetics has not been quantified. Methods Three-dimensional lower extremity kinematics and kinetics and electromyographic (EMG) data were obtained from 20 healthy adults during their performance of FSU, LSU, and FSD exercises. The step height for each participant was adjusted to permit a standardized knee flexion angle of 45°. A previously described biomechanical model of the Patellofemoral Joint was used to quantify PFJRF and PFJS during each task. Peak PFJRF and PFJS during the concentric and eccentric phases of each step task were compared using a 2-factor analysis of variance (ANOV...

Andrew A. Amis - One of the best experts on this subject based on the ideXlab platform.

  • a cadaveric model to evaluate the effect of unloading the medial quadriceps on patellar tracking and Patellofemoral Joint pressure and stability
    Journal of Experimental Orthopaedics, 2018
    Co-Authors: Joanna M. Stephen, Andy Williams, Punyawan Lumpaopong, Avinash Alva, Andrew A. Amis
    Abstract:

    Vastus Medialis Muscles (VMM) damage has been widely identified following patellar dislocation. Rehabilitation programmes have been suggested to strengthen the VMM and reduce clinical symptoms of pain and instability. This controlled laboratory study investigated the hypothesis that reduced Vastus Medialis Obliquus (VMO) and Vastus Medialis Longus (VML) muscle tension would alter patellar tracking, stability and PFJ contact pressures. Nine fresh-frozen dissected cadaveric knees were mounted in a rig with the quadriceps and iliotibial band loaded to 205 N. An optical tracking system measured Joint kinematics and pressure sensitive film between the patella and trochlea measured PFJ contact pressures. Measurements were repeated for three conditions: 1. With all quadriceps heads and iliotibial band (ITB) loaded; 2. as 1, but with the VMO muscle unloaded and 3. as 1, but with the VMO and VML unloaded. Measurements were also repeated for the three conditions with a 10 N lateral displacement force applied to the patella. Reduction of VMM tension resulted in significant increases in lateral patellar tilt (2.8°) and translation (4 mm), with elevated lateral and reduced medial Joint contact pressures from 0.48 to 0.14 MPa, and reduced patellar stability (all p < 0.05). These findings provide basic scientific rationale to support the role of quadriceps strengthening to resist patellar lateral maltracking and rebalance the articular contact pressure away from the lateral facet in patients with normal Patellofemoral Joint anatomy.

  • Effect of anterolateral complex sectioning and tenodesis on patellar kinematics and Patellofemoral Joint contact pressures
    'SAGE Publications', 2018
    Co-Authors: Inderhaug E, Jm Stephen, Williams A, Andrew A. Amis
    Abstract:

    Background: Anterolateral complex injuries are becoming more recognized. While these are known to affect tibiofemoral mechanics, it is not known how they affect Patellofemoral Joint behavior. Purpose: To determine the effect of (1) sectioning the anterolateral complex and (2) performing a MacIntosh tenodesis under various conditions on Patellofemoral contact mechanics and kinematics. Study Design: Controlled laboratory study. Methods: Eight fresh-frozen cadaveric knees were tested in a customized rig, with the femur fixed and tibia free to move, with optical tracking to record patellar kinematics and with thin pressure sensors to record Patellofemoral contact pressures at 0°, 30°, 60°, and 90° of knee flexion. The quadriceps and iliotibial tract were loaded with 205 N throughout testing. Intact and anterolateral complex–sectioned states were tested, followed by 4 randomized tenodeses applying 20- and 80-N graft tension, each with the tibia in its neutral intact alignment or left free to rotate. Statistical analyses were undertaken with repeated measures analysis of variance, Bonferroni post hoc analysis, and paired samples t tests. Results: Patellar kinematics and contact pressures were not significantly altered after sectioning of the anterolateral complex (all: P > .05). Similarly, they were not significantly different from the intact knee in tenodeses performed when fixed tibial rotation was combined with 20- or 80-N graft tension (all: P > .05). However, grafts tensioned with 20 N and 80 N while the tibia was free hanging resulted in significant increases in lateral patellar tilt (P < .05), and significantly elevated lateral peak Patellofemoral pressures (P < .05) were observed for 80 N. Conclusion: This work did not find that an anterolateral injury altered Patellofemoral mechanics or kinematics, but adding a lateral tenodesis can elevate lateral contact pressures and induce lateral patellar tilting if the tibia is pulled into external rotation by the tenodesis. Although these in vitro changes were small and might not be relevant in a fully loaded knee, controlling the position of the tibia at graft fixation is effective in avoiding overconstraint at time zero in a lateral tenodesis. Clinical Relevance: Small changes in lateral patellar tilt and Patellofemoral contact pressures were found at time zero with a MacIntosh tenodesis. These changes were eliminated when the tibia was held in neutral rotation at the time of graft fixation. The risk of overconstraint after a lateral tenodesis therefore seems low and in accordance with recent published reports

  • the effect of tibial tuberosity medialization and lateralization on Patellofemoral Joint kinematics contact mechanics and stability
    American Journal of Sports Medicine, 2015
    Co-Authors: Joanna M. Stephen, Andy Williams, Punyawan Lumpaopong, Alexander L Dodds, Andrew A. Amis
    Abstract:

    Background:Tibial tuberosity (TT) transfer is a common procedure to treat Patellofemoral instability in patients with elevated TT–trochlear groove (TG) distances. However, the effects of TT lateralization or medialization on patellar stability, kinematics, and contact mechanics remain unclear.Hypothesis:Progressive medialization and lateralization will have increasingly adverse effects on Patellofemoral Joint kinematics, contact mechanics, and stability.Study Design:Controlled laboratory study.Methods:Eight fresh-frozen cadaveric knees were placed on a testing rig, with a fixed femur and tibia mobile through 90° of flexion. Individual quadriceps heads and the iliotibial band were separated and loaded with 205 N in anatomic directions using a weighted pulley system. Patellofemoral contact pressures and patellar tracking were measured at 0°, 10°, 20°, 30°, 60°, and 90° of flexion using pressure-sensitive film behind the patella and an optical tracking system. The intact knee was measured with and without a ...

  • sectioning the medial Patellofemoral ligament alters Patellofemoral Joint kinematics and contact mechanics
    Journal of Orthopaedic Research, 2013
    Co-Authors: Joanna M. Stephen, Punyawan Lumpaopong, Deiary F Kader, David J Deehan, Andrew A. Amis
    Abstract:

    Medial Patellofemoral ligament (MPFL) disruption may alter Patellofemoral Joint (PFJ) kinematics and contact mechanics, potentially causing pain and Joint degeneration. In this controlled laboratory study, we investigated the hypothesis that MPFL transection would change patellar tracking and PFJ contact pressures and increase the distance between the attachment points of the MPFL. Eight fresh frozen dissected cadaveric knees were mounted in a rig with the quadriceps and ITB loaded to 205 N. An optical tracking system measured Joint kinematics, and pressure sensitive film between the patella and trochlea measured PFJ contact pressures. Length patterns of the distance between the femoral and patellar attachments of the MPFL were measured using a suture led to a linear displacement transducer. Measurements were repeated with the MPFL intact and following MPFL transection. A significant increase in the distance between the patellar and femoral MPFL attachment points was noted following transection (p < 0.05). MPFL transection resulted in significantly increased lateral translation and lateral tilt of the patella in early flexion (p < 0.05). Peak and mean medial PFJ contact pressures were significantly reduced and peak lateral contact pressures significantly elevated in early knee flexion following MPFL transection (p < 0.05). MPFL transection resulted in significant alterations to PFJ tracking and contact pressures, which may affect articular cartilage health. © 2013 Orthopaedic Research Society Published by Wiley Periodicals, Inc. J Orthop Res 31:1423–1429, 2013

  • the effects of articular retinacular or muscular deficiencies on Patellofemoral Joint stability a biomechanical study in vitro
    Journal of Bone and Joint Surgery-british Volume, 2005
    Co-Authors: Wongwit Senavongse, Andrew A. Amis
    Abstract:

    Normal function of the Patellofemoral Joint is maintained by a complex interaction between soft tissues and articular surfaces. No quantitative data have been found on the relative contributions of these structures to patellar stability. Eight knees were studied using a materials testing machine to displace the patella 10 mm laterally and medially and measure the force required. Patellar stability was tested from 0° to 90° knee flexion with the quadriceps tensed to 175 N. Four conditions were examined: intact, vastus medialis obliquus relaxed, flat lateral condyle, and ruptured medial retinaculae. Abnormal trochlear geometry reduced the lateral stability by 70% at 30° flexion, while relaxation of vastus medialis obliquus caused a 30% reduction. Ruptured medial retinaculae had the largest effect at 0° flexion with 49% reduction. There was no effect on medial stability. There is a complex interaction between these structures, with their contributions to loss of lateral patellar stability varying with knee f...

Scott L Delp - One of the best experts on this subject based on the ideXlab platform.

  • patients with Patellofemoral pain exhibit elevated bone metabolic activity at the Patellofemoral Joint
    Journal of Orthopaedic Research, 2012
    Co-Authors: Christine E Draper, Thor F Besier, Garry E Gold, Gary S Beaupre, Scott L Delp, Michael Fredericson, Andrew Quon
    Abstract:

    Patellofemoral pain is characterized by pain behind the kneecap and is often thought to be due to high stress at the Patellofemoral Joint. While we cannot measure bone stress in vivo, we can visualize bone metabolic activity using 18 F NaF PET/CT, which may be related to bone stress. Our goals were to use 18 F NaF PET/CT to evaluate whether subjects with Patellofemoral pain exhibit elevated bone metabolic activity and to determine whether bone metabolic activity correlates with pain intensity. We examined 20 subjects diagnosed with Patellofemoral pain. All subjects received an 18 F NaF PET/CT scan of their knees. Uptake of 18 F NaF in the patella and trochlea was quantified by computing the standardized uptake value and normalizing by the background tracer uptake in bone. We detected increased tracer uptake in 85% of the painful knees examined. We found that the painful knees exhibited increased tracer uptake compared to the pain-free knees of four subjects with unilateral pain (P ¼ 0.0006). We also found a correlation between increasing tracer uptake and increasing pain intensity (r 2 ¼ 0.55; P ¼ 0.0005). The implication of these results is that Patellofemoral pain may be related to bone metabolic activity at the Patellofemoral Joint. 2011 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 30:209-213, 2012

  • the influence of femoral internal and external rotation on cartilage stresses within the Patellofemoral Joint
    Journal of Orthopaedic Research, 2008
    Co-Authors: Thor F Besier, Garry E Gold, Scott L Delp, Michael Fredericson, Gary S Beaupre
    Abstract:

    Internal and external rotation of the femur plays an important role in defining the orientation of the Patellofemoral Joint, influencing contact areas, pressures, and cartilage stress distributions. The purpose of this study was to determine the influence of femoral internal and external rotation on stresses in the Patellofemoral cartilage. We constructed finite element models of the Patellofemoral Joint using magnetic resonance (MR) images from 16 volunteers (8 male and 8 female). Subjects performed an upright weight-bearing squat with the knee at 608 of flexion inside an open-MR scanner and in a gait laboratory. Quadriceps muscle forces were estimated for each subject using an electromyographic-driven model and input to a finite element analysis. Hydrostatic and octahedral shear stresses within the cartilage were modeled with the tibiofemoral Joint in a ''neutral'' position and also with the femur rotated internally or externally by 58 increments to � 158. Cartilage stresses were more sensitive to external rotation of the femur, compared with internal rotation, with large variation across subjects. Peak patellar shear stresses increased more than 10% with 158 of external rotation in 75% of the subjects. Shear stresses were higher in the patellar cartilage compared to the femoral cartilage and patellar cartilage stresses were more sensitive to femoral rotation compared with femoral cartilage stress. Large variation in the cartilage stress response between individuals reflects the complex nature of the extensor mechanism and has clinical relevance when considering treatment strategies designed to reduce cartilage stresses by altering femoral internal and external rotation. 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 26:1627- 1635, 2008 Articular cartilage plays an integral role in the distribution of Joint loads to underlying bone, and displays unique mechanical properties that allow it to sustain considerable repetitive loads. This is particu- larly important at the Patellofemoral Joint, which experiences contact forces greater than body weight (BW) during everyday activities such as walking (� 1.2 � BW), 1 climbing stairs (3.0 to 3.5 � BW), 2,3 or running (7.0 to 11.0 � BW). 4 Any change in the mechanical environment, via altered Joint kinematics or load distribution, will affect the stress state of the cartilage, subchondral bone, and cancellous bone, ultimately influencing the physiology and morphology

  • the influence of femoral internal and external rotation on cartilage stresses within the Patellofemoral Joint
    Journal of Orthopaedic Research, 2008
    Co-Authors: Thor F Besier, Garry E Gold, Scott L Delp, Michael Fredericson, Gary S Beaupre
    Abstract:

    Internal and external rotation of the femur plays an important role in defining the orientation of the Patellofemoral Joint, influencing contact areas, pressures, and cartilage stress distributions. The purpose of this study was to determine the influence of femoral internal and external rotation on stresses in the Patellofemoral cartilage. We constructed finite element models of the Patellofemoral Joint using magnetic resonance (MR) images from 16 volunteers (8 male and 8 female). Subjects performed an upright weight-bearing squat with the knee at 60 degrees of flexion inside an open-MR scanner and in a gait laboratory. Quadriceps muscle forces were estimated for each subject using an electromyographic-driven model and input to a finite element analysis. Hydrostatic and octahedral shear stresses within the cartilage were modeled with the tibiofemoral Joint in a "neutral" position and also with the femur rotated internally or externally by 5 degrees increments to +/-15 degrees . Cartilage stresses were more sensitive to external rotation of the femur, compared with internal rotation, with large variation across subjects. Peak patellar shear stresses increased more than 10% with 15 degrees of external rotation in 75% of the subjects. Shear stresses were higher in the patellar cartilage compared to the femoral cartilage and patellar cartilage stresses were more sensitive to femoral rotation compared with femoral cartilage stress. Large variation in the cartilage stress response between individuals reflects the complex nature of the extensor mechanism and has clinical relevance when considering treatment strategies designed to reduce cartilage stresses by altering femoral internal and external rotation.

  • a modeling framework to estimate Patellofemoral Joint cartilage stress in vivo
    Medicine and Science in Sports and Exercise, 2005
    Co-Authors: Thor F Besier, Garry E Gold, Gary S Beaupre, Scott L Delp
    Abstract:

    BESIER, T. F., G. E. GOLD, G. S. BEAUPRE´, and S. L. DELP. A Modeling Framework to Estimate Patellofemoral Joint Cartilage Stress In Vivo. Med. Sci. Sports Med., Vol. 37, No. 11, pp. 1924–1930, 2005. Purpose: Patellofemoral (PF) pain is common among athletes and may be caused by increased subchondral bone stress as a result of increased stress in the cartilage of the femur or patella. This article presents a modeling pipeline to estimate in vivo cartilage stress in the PF Joint. Methods: The modeling pipeline uses the finite element method to calculate stresses and strains in the PF Joint cartilage. Model inputs include an accurate geometrical representation of the bones and cartilage from magnetic resonance imaging (MRI), cartilage material properties, and an estimate of muscle forces from an EMG-driven musculoskeletal model. Validation is performed using PF Joint contact area and patellar orientation measured from upright, weight-bearing MRI. Preliminary data from an active, pain-free subject illustrate the modeling pipeline to calculate cartilage stress during a static squat. Results: The quasistatic finite element simulation reproduced the orientation of the patella to within 2.1 mm and predicted the PF Joint contact area to within 2.3%. Octahedral shear stresses were highest in the central, lateral aspect of the patella cartilage with a peak of 2.5 MPa. The corresponding stresses in the femoral cartilage reached only 2.0 MPa. However, peak hydrostatic pressures were higher within the femoral cartilage (3.5 MPa) than the patellar cartilage (2.3 MPa). Conclusion: The methods presented in this article offer a novel approach to calculate PF Joint cartilage stress in vivo. Future efforts will use this modeling pipeline to further our knowledge of PF pain and potential rehabilitation strategies. Key Words: Patellofemoral PAIN, WEIGHT-BEARING MRI, FINITE ELEMENT MODEL, EMG-DRIVEN MODEL

  • Patellofemoral Joint contact area increases with knee flexion and weight bearing
    Journal of Orthopaedic Research, 2005
    Co-Authors: Thor F Besier, Christine E Draper, Garry E Gold, Gary S Beaupre, Scott L Delp
    Abstract:

    Patellofemoral pain is a common and debilitating disorder. Elevated cartilage stress of the Patellofemoral Joint is hypothesized to play a role in the onset of pain. Estimating cartilage stress requires accurate measurements of contact area. The purpose of this study was to estimate Patellofemoral Joint contact areas in a group of healthy, pain-free subjects during upright, weight-bearing conditions. Sixteen subjects (8 female, 8 male) were scanned in a GE Signa SP open configuration MRI scanner, which allowed subjects to stand or squat while reclining 25� from vertical with the knee positioned at 0� ,3 0� ,o r 60� of flexion. A custom-built backrest enabled subjects to be scanned without motion artifact in both weight-bearing (0.45 body weight per leg) and reduced loading conditions (unloaded at 0.15 body weight) at each knee flexion posture. Male subjects displayed mean unloaded Patellofemoral Joint contact areas of 210, 414, and 520 mm 2 at 0� ,3 0� and 60� of knee flexion, respectively. Female subjects unloaded contact areas were similar at full extension (0� ), but significantly smaller at 30� and 60� (p < 0.01), with mean values of 269 and 396 mm 2 , respectively. When normalized by patellar dimensions (height · width), contact areas were not different between genders. Under weight-bearing conditions, contact areas increased by an average of 24% (p < 0.05). This study highlights the differences in Patellofemoral Joint contact area between gender, knee flexion postures, and physiologic loading conditions. � 2004 Orthopaedic Research Society. Published by Elsevier Ltd. All rights reserved.

Gary S Beaupre - One of the best experts on this subject based on the ideXlab platform.

  • patients with Patellofemoral pain exhibit elevated bone metabolic activity at the Patellofemoral Joint
    Journal of Orthopaedic Research, 2012
    Co-Authors: Christine E Draper, Thor F Besier, Garry E Gold, Gary S Beaupre, Scott L Delp, Michael Fredericson, Andrew Quon
    Abstract:

    Patellofemoral pain is characterized by pain behind the kneecap and is often thought to be due to high stress at the Patellofemoral Joint. While we cannot measure bone stress in vivo, we can visualize bone metabolic activity using 18 F NaF PET/CT, which may be related to bone stress. Our goals were to use 18 F NaF PET/CT to evaluate whether subjects with Patellofemoral pain exhibit elevated bone metabolic activity and to determine whether bone metabolic activity correlates with pain intensity. We examined 20 subjects diagnosed with Patellofemoral pain. All subjects received an 18 F NaF PET/CT scan of their knees. Uptake of 18 F NaF in the patella and trochlea was quantified by computing the standardized uptake value and normalizing by the background tracer uptake in bone. We detected increased tracer uptake in 85% of the painful knees examined. We found that the painful knees exhibited increased tracer uptake compared to the pain-free knees of four subjects with unilateral pain (P ¼ 0.0006). We also found a correlation between increasing tracer uptake and increasing pain intensity (r 2 ¼ 0.55; P ¼ 0.0005). The implication of these results is that Patellofemoral pain may be related to bone metabolic activity at the Patellofemoral Joint. 2011 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 30:209-213, 2012

  • the influence of femoral internal and external rotation on cartilage stresses within the Patellofemoral Joint
    Journal of Orthopaedic Research, 2008
    Co-Authors: Thor F Besier, Garry E Gold, Scott L Delp, Michael Fredericson, Gary S Beaupre
    Abstract:

    Internal and external rotation of the femur plays an important role in defining the orientation of the Patellofemoral Joint, influencing contact areas, pressures, and cartilage stress distributions. The purpose of this study was to determine the influence of femoral internal and external rotation on stresses in the Patellofemoral cartilage. We constructed finite element models of the Patellofemoral Joint using magnetic resonance (MR) images from 16 volunteers (8 male and 8 female). Subjects performed an upright weight-bearing squat with the knee at 608 of flexion inside an open-MR scanner and in a gait laboratory. Quadriceps muscle forces were estimated for each subject using an electromyographic-driven model and input to a finite element analysis. Hydrostatic and octahedral shear stresses within the cartilage were modeled with the tibiofemoral Joint in a ''neutral'' position and also with the femur rotated internally or externally by 58 increments to � 158. Cartilage stresses were more sensitive to external rotation of the femur, compared with internal rotation, with large variation across subjects. Peak patellar shear stresses increased more than 10% with 158 of external rotation in 75% of the subjects. Shear stresses were higher in the patellar cartilage compared to the femoral cartilage and patellar cartilage stresses were more sensitive to femoral rotation compared with femoral cartilage stress. Large variation in the cartilage stress response between individuals reflects the complex nature of the extensor mechanism and has clinical relevance when considering treatment strategies designed to reduce cartilage stresses by altering femoral internal and external rotation. 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 26:1627- 1635, 2008 Articular cartilage plays an integral role in the distribution of Joint loads to underlying bone, and displays unique mechanical properties that allow it to sustain considerable repetitive loads. This is particu- larly important at the Patellofemoral Joint, which experiences contact forces greater than body weight (BW) during everyday activities such as walking (� 1.2 � BW), 1 climbing stairs (3.0 to 3.5 � BW), 2,3 or running (7.0 to 11.0 � BW). 4 Any change in the mechanical environment, via altered Joint kinematics or load distribution, will affect the stress state of the cartilage, subchondral bone, and cancellous bone, ultimately influencing the physiology and morphology

  • the influence of femoral internal and external rotation on cartilage stresses within the Patellofemoral Joint
    Journal of Orthopaedic Research, 2008
    Co-Authors: Thor F Besier, Garry E Gold, Scott L Delp, Michael Fredericson, Gary S Beaupre
    Abstract:

    Internal and external rotation of the femur plays an important role in defining the orientation of the Patellofemoral Joint, influencing contact areas, pressures, and cartilage stress distributions. The purpose of this study was to determine the influence of femoral internal and external rotation on stresses in the Patellofemoral cartilage. We constructed finite element models of the Patellofemoral Joint using magnetic resonance (MR) images from 16 volunteers (8 male and 8 female). Subjects performed an upright weight-bearing squat with the knee at 60 degrees of flexion inside an open-MR scanner and in a gait laboratory. Quadriceps muscle forces were estimated for each subject using an electromyographic-driven model and input to a finite element analysis. Hydrostatic and octahedral shear stresses within the cartilage were modeled with the tibiofemoral Joint in a "neutral" position and also with the femur rotated internally or externally by 5 degrees increments to +/-15 degrees . Cartilage stresses were more sensitive to external rotation of the femur, compared with internal rotation, with large variation across subjects. Peak patellar shear stresses increased more than 10% with 15 degrees of external rotation in 75% of the subjects. Shear stresses were higher in the patellar cartilage compared to the femoral cartilage and patellar cartilage stresses were more sensitive to femoral rotation compared with femoral cartilage stress. Large variation in the cartilage stress response between individuals reflects the complex nature of the extensor mechanism and has clinical relevance when considering treatment strategies designed to reduce cartilage stresses by altering femoral internal and external rotation.

  • a modeling framework to estimate Patellofemoral Joint cartilage stress in vivo
    Medicine and Science in Sports and Exercise, 2005
    Co-Authors: Thor F Besier, Garry E Gold, Gary S Beaupre, Scott L Delp
    Abstract:

    BESIER, T. F., G. E. GOLD, G. S. BEAUPRE´, and S. L. DELP. A Modeling Framework to Estimate Patellofemoral Joint Cartilage Stress In Vivo. Med. Sci. Sports Med., Vol. 37, No. 11, pp. 1924–1930, 2005. Purpose: Patellofemoral (PF) pain is common among athletes and may be caused by increased subchondral bone stress as a result of increased stress in the cartilage of the femur or patella. This article presents a modeling pipeline to estimate in vivo cartilage stress in the PF Joint. Methods: The modeling pipeline uses the finite element method to calculate stresses and strains in the PF Joint cartilage. Model inputs include an accurate geometrical representation of the bones and cartilage from magnetic resonance imaging (MRI), cartilage material properties, and an estimate of muscle forces from an EMG-driven musculoskeletal model. Validation is performed using PF Joint contact area and patellar orientation measured from upright, weight-bearing MRI. Preliminary data from an active, pain-free subject illustrate the modeling pipeline to calculate cartilage stress during a static squat. Results: The quasistatic finite element simulation reproduced the orientation of the patella to within 2.1 mm and predicted the PF Joint contact area to within 2.3%. Octahedral shear stresses were highest in the central, lateral aspect of the patella cartilage with a peak of 2.5 MPa. The corresponding stresses in the femoral cartilage reached only 2.0 MPa. However, peak hydrostatic pressures were higher within the femoral cartilage (3.5 MPa) than the patellar cartilage (2.3 MPa). Conclusion: The methods presented in this article offer a novel approach to calculate PF Joint cartilage stress in vivo. Future efforts will use this modeling pipeline to further our knowledge of PF pain and potential rehabilitation strategies. Key Words: Patellofemoral PAIN, WEIGHT-BEARING MRI, FINITE ELEMENT MODEL, EMG-DRIVEN MODEL

  • Patellofemoral Joint contact area increases with knee flexion and weight bearing
    Journal of Orthopaedic Research, 2005
    Co-Authors: Thor F Besier, Christine E Draper, Garry E Gold, Gary S Beaupre, Scott L Delp
    Abstract:

    Patellofemoral pain is a common and debilitating disorder. Elevated cartilage stress of the Patellofemoral Joint is hypothesized to play a role in the onset of pain. Estimating cartilage stress requires accurate measurements of contact area. The purpose of this study was to estimate Patellofemoral Joint contact areas in a group of healthy, pain-free subjects during upright, weight-bearing conditions. Sixteen subjects (8 female, 8 male) were scanned in a GE Signa SP open configuration MRI scanner, which allowed subjects to stand or squat while reclining 25� from vertical with the knee positioned at 0� ,3 0� ,o r 60� of flexion. A custom-built backrest enabled subjects to be scanned without motion artifact in both weight-bearing (0.45 body weight per leg) and reduced loading conditions (unloaded at 0.15 body weight) at each knee flexion posture. Male subjects displayed mean unloaded Patellofemoral Joint contact areas of 210, 414, and 520 mm 2 at 0� ,3 0� and 60� of knee flexion, respectively. Female subjects unloaded contact areas were similar at full extension (0� ), but significantly smaller at 30� and 60� (p < 0.01), with mean values of 269 and 396 mm 2 , respectively. When normalized by patellar dimensions (height · width), contact areas were not different between genders. Under weight-bearing conditions, contact areas increased by an average of 24% (p < 0.05). This study highlights the differences in Patellofemoral Joint contact area between gender, knee flexion postures, and physiologic loading conditions. � 2004 Orthopaedic Research Society. Published by Elsevier Ltd. All rights reserved.

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  • patients with Patellofemoral pain exhibit elevated bone metabolic activity at the Patellofemoral Joint
    Journal of Orthopaedic Research, 2012
    Co-Authors: Christine E Draper, Thor F Besier, Garry E Gold, Gary S Beaupre, Scott L Delp, Michael Fredericson, Andrew Quon
    Abstract:

    Patellofemoral pain is characterized by pain behind the kneecap and is often thought to be due to high stress at the Patellofemoral Joint. While we cannot measure bone stress in vivo, we can visualize bone metabolic activity using 18 F NaF PET/CT, which may be related to bone stress. Our goals were to use 18 F NaF PET/CT to evaluate whether subjects with Patellofemoral pain exhibit elevated bone metabolic activity and to determine whether bone metabolic activity correlates with pain intensity. We examined 20 subjects diagnosed with Patellofemoral pain. All subjects received an 18 F NaF PET/CT scan of their knees. Uptake of 18 F NaF in the patella and trochlea was quantified by computing the standardized uptake value and normalizing by the background tracer uptake in bone. We detected increased tracer uptake in 85% of the painful knees examined. We found that the painful knees exhibited increased tracer uptake compared to the pain-free knees of four subjects with unilateral pain (P ¼ 0.0006). We also found a correlation between increasing tracer uptake and increasing pain intensity (r 2 ¼ 0.55; P ¼ 0.0005). The implication of these results is that Patellofemoral pain may be related to bone metabolic activity at the Patellofemoral Joint. 2011 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 30:209-213, 2012

  • the influence of femoral internal and external rotation on cartilage stresses within the Patellofemoral Joint
    Journal of Orthopaedic Research, 2008
    Co-Authors: Thor F Besier, Garry E Gold, Scott L Delp, Michael Fredericson, Gary S Beaupre
    Abstract:

    Internal and external rotation of the femur plays an important role in defining the orientation of the Patellofemoral Joint, influencing contact areas, pressures, and cartilage stress distributions. The purpose of this study was to determine the influence of femoral internal and external rotation on stresses in the Patellofemoral cartilage. We constructed finite element models of the Patellofemoral Joint using magnetic resonance (MR) images from 16 volunteers (8 male and 8 female). Subjects performed an upright weight-bearing squat with the knee at 608 of flexion inside an open-MR scanner and in a gait laboratory. Quadriceps muscle forces were estimated for each subject using an electromyographic-driven model and input to a finite element analysis. Hydrostatic and octahedral shear stresses within the cartilage were modeled with the tibiofemoral Joint in a ''neutral'' position and also with the femur rotated internally or externally by 58 increments to � 158. Cartilage stresses were more sensitive to external rotation of the femur, compared with internal rotation, with large variation across subjects. Peak patellar shear stresses increased more than 10% with 158 of external rotation in 75% of the subjects. Shear stresses were higher in the patellar cartilage compared to the femoral cartilage and patellar cartilage stresses were more sensitive to femoral rotation compared with femoral cartilage stress. Large variation in the cartilage stress response between individuals reflects the complex nature of the extensor mechanism and has clinical relevance when considering treatment strategies designed to reduce cartilage stresses by altering femoral internal and external rotation. 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 26:1627- 1635, 2008 Articular cartilage plays an integral role in the distribution of Joint loads to underlying bone, and displays unique mechanical properties that allow it to sustain considerable repetitive loads. This is particu- larly important at the Patellofemoral Joint, which experiences contact forces greater than body weight (BW) during everyday activities such as walking (� 1.2 � BW), 1 climbing stairs (3.0 to 3.5 � BW), 2,3 or running (7.0 to 11.0 � BW). 4 Any change in the mechanical environment, via altered Joint kinematics or load distribution, will affect the stress state of the cartilage, subchondral bone, and cancellous bone, ultimately influencing the physiology and morphology

  • the influence of femoral internal and external rotation on cartilage stresses within the Patellofemoral Joint
    Journal of Orthopaedic Research, 2008
    Co-Authors: Thor F Besier, Garry E Gold, Scott L Delp, Michael Fredericson, Gary S Beaupre
    Abstract:

    Internal and external rotation of the femur plays an important role in defining the orientation of the Patellofemoral Joint, influencing contact areas, pressures, and cartilage stress distributions. The purpose of this study was to determine the influence of femoral internal and external rotation on stresses in the Patellofemoral cartilage. We constructed finite element models of the Patellofemoral Joint using magnetic resonance (MR) images from 16 volunteers (8 male and 8 female). Subjects performed an upright weight-bearing squat with the knee at 60 degrees of flexion inside an open-MR scanner and in a gait laboratory. Quadriceps muscle forces were estimated for each subject using an electromyographic-driven model and input to a finite element analysis. Hydrostatic and octahedral shear stresses within the cartilage were modeled with the tibiofemoral Joint in a "neutral" position and also with the femur rotated internally or externally by 5 degrees increments to +/-15 degrees . Cartilage stresses were more sensitive to external rotation of the femur, compared with internal rotation, with large variation across subjects. Peak patellar shear stresses increased more than 10% with 15 degrees of external rotation in 75% of the subjects. Shear stresses were higher in the patellar cartilage compared to the femoral cartilage and patellar cartilage stresses were more sensitive to femoral rotation compared with femoral cartilage stress. Large variation in the cartilage stress response between individuals reflects the complex nature of the extensor mechanism and has clinical relevance when considering treatment strategies designed to reduce cartilage stresses by altering femoral internal and external rotation.

  • a modeling framework to estimate Patellofemoral Joint cartilage stress in vivo
    Medicine and Science in Sports and Exercise, 2005
    Co-Authors: Thor F Besier, Garry E Gold, Gary S Beaupre, Scott L Delp
    Abstract:

    BESIER, T. F., G. E. GOLD, G. S. BEAUPRE´, and S. L. DELP. A Modeling Framework to Estimate Patellofemoral Joint Cartilage Stress In Vivo. Med. Sci. Sports Med., Vol. 37, No. 11, pp. 1924–1930, 2005. Purpose: Patellofemoral (PF) pain is common among athletes and may be caused by increased subchondral bone stress as a result of increased stress in the cartilage of the femur or patella. This article presents a modeling pipeline to estimate in vivo cartilage stress in the PF Joint. Methods: The modeling pipeline uses the finite element method to calculate stresses and strains in the PF Joint cartilage. Model inputs include an accurate geometrical representation of the bones and cartilage from magnetic resonance imaging (MRI), cartilage material properties, and an estimate of muscle forces from an EMG-driven musculoskeletal model. Validation is performed using PF Joint contact area and patellar orientation measured from upright, weight-bearing MRI. Preliminary data from an active, pain-free subject illustrate the modeling pipeline to calculate cartilage stress during a static squat. Results: The quasistatic finite element simulation reproduced the orientation of the patella to within 2.1 mm and predicted the PF Joint contact area to within 2.3%. Octahedral shear stresses were highest in the central, lateral aspect of the patella cartilage with a peak of 2.5 MPa. The corresponding stresses in the femoral cartilage reached only 2.0 MPa. However, peak hydrostatic pressures were higher within the femoral cartilage (3.5 MPa) than the patellar cartilage (2.3 MPa). Conclusion: The methods presented in this article offer a novel approach to calculate PF Joint cartilage stress in vivo. Future efforts will use this modeling pipeline to further our knowledge of PF pain and potential rehabilitation strategies. Key Words: Patellofemoral PAIN, WEIGHT-BEARING MRI, FINITE ELEMENT MODEL, EMG-DRIVEN MODEL

  • Patellofemoral Joint contact area increases with knee flexion and weight bearing
    Journal of Orthopaedic Research, 2005
    Co-Authors: Thor F Besier, Christine E Draper, Garry E Gold, Gary S Beaupre, Scott L Delp
    Abstract:

    Patellofemoral pain is a common and debilitating disorder. Elevated cartilage stress of the Patellofemoral Joint is hypothesized to play a role in the onset of pain. Estimating cartilage stress requires accurate measurements of contact area. The purpose of this study was to estimate Patellofemoral Joint contact areas in a group of healthy, pain-free subjects during upright, weight-bearing conditions. Sixteen subjects (8 female, 8 male) were scanned in a GE Signa SP open configuration MRI scanner, which allowed subjects to stand or squat while reclining 25� from vertical with the knee positioned at 0� ,3 0� ,o r 60� of flexion. A custom-built backrest enabled subjects to be scanned without motion artifact in both weight-bearing (0.45 body weight per leg) and reduced loading conditions (unloaded at 0.15 body weight) at each knee flexion posture. Male subjects displayed mean unloaded Patellofemoral Joint contact areas of 210, 414, and 520 mm 2 at 0� ,3 0� and 60� of knee flexion, respectively. Female subjects unloaded contact areas were similar at full extension (0� ), but significantly smaller at 30� and 60� (p < 0.01), with mean values of 269 and 396 mm 2 , respectively. When normalized by patellar dimensions (height · width), contact areas were not different between genders. Under weight-bearing conditions, contact areas increased by an average of 24% (p < 0.05). This study highlights the differences in Patellofemoral Joint contact area between gender, knee flexion postures, and physiologic loading conditions. � 2004 Orthopaedic Research Society. Published by Elsevier Ltd. All rights reserved.