Biomechanics of Osteoarthritis:Analyzing knee forces and functions

Jill Higginson, PhD

Assistant ProfessorDepartment of Mechanical Engineering

University of Delaware

Arthritis and Americans

67 million persons2030

46 million persons2006

Osteoarthritis (OA)

Degenerative joint disease involving cartilage deteriorationThin cartilage with grooves and fragmentsDebris expedites deterioration

Knee osteoarthritisOA severity depends on cartilage thickness, presence of osteophytesScored on Kellgren-Lawrence (KL) scale from x-ray

KL=0 KL=1 KL=3KL=2

Implications of OA

Leading cause of disabilityLimits activities of daily living>50% of adults with OA are

Risk factorsModifiable

Excess body mass Joint injury (sports, work, trauma)Occupation (due to excessive mechanical stress: hard labor, heavy lifting, knee bending, repetitive motion) Structural malalignment, muscle weakness

Non-modifiableGender (women higher risk) Age (increases with age and levels around age 75)Race (some Asian populations have lower risk)Genetic predisposition

Other possible risk factorsEstrogen deficiency (ERT may reduce risk of knee/hip OA)Osteoporosis (inversely related to OA)Vitamins C, E and D equivocal reports

www.cdc.gov

Pathomechanics

Andriacchi et al., 2004

Pathomechanics

Andriacchi et al., 2004

MotivationMuscles contribute significantly to joint loads and activity can be modified with non-surgical interventionResponse to challenge may identify limiting factors (i.e. what compensatory strategies are used?)Loading patterns should be related to cartilage deterioration

OutlineGait analysis

Effect of OA severity on hip, knee and ankle contributionsResponse to challenge

Modeling and simulationJoint contact forces depend on muscle activity

ImagingCartilage geometry vs OA progression

Experimental design

ImagingCartilageMappingGait analysis

MusculoskeletalSimulation

JOINT CONTACT FORCES CARTILAGE GEOMETRY

Subject recruitmentGoal: 60 OA, 20 healthy subjects

Age 30-85Tracked for 2 yearsNo major orthopedic, neuromuscular or cardiovascular conditions

Bilateral x-ray (KL grade)Activity surveryStrength testing

Gait analysis

Ryp

Rxp

mgMd

Ryd

RxdRzd

ax

ay

az

MpRzp

Gait analysisInstrumented treadmillFour walking conditions (30 sec)

Self-selected walking speedControl speed (0.8 m/s)Fastest possible walking speed15% load carriage at SS speed

Safety harnessGRFs, s, EMG

Quadriceps avoidance?

Quadriceps avoidance!

(Nm/BW) Torque Volitional QuadricepsMax (Nm/BW)Moment Flexion KneePeak

=(QE) Effort Quadriceps

Total support moment

AB

Total support moment

Response to challenge

Response to challenge

From gait analysis

Individuals with severe OA exhibitQuadriceps avoidanceReduced contribution of knee extensors to COM support (supplemented by hip)Reduced knee loads (forces and moments) when challenged to walk quickly

What is the role of muscles in compensatory strategies?

Experimental design

ImagingCartilageMappingGait analysis

MusculoskeletalSimulation

JOINT CONTACT FORCES CARTILAGE GEOMETRY

Musculoskeletal Simulation

With inverse dynamics, we measure position, velocity and acceleration and solve for reaction forces and moments

With forward dynamics, we estimate and apply internal (muscle) forces to solve for resultant movement patterns

Generation of movement

activationdynamics

muscletendon

dynamics

musculo-skeletalsystem

movement

CNS

externalforces

e(t) a(t) F(t) (t)

,, &&&

http://www.designtutorials.info/images/movement-initial.jpghttp://news-service.stanford.edu/news/2007/january17/gifs/movement_golferone.jpghttp://images.google.com/imgres?imgurl=http://content.answers.com/main/content/wp/en-commons/thumb/9/9f/200px-Muybridge_race_horse_animated.gif&imgrefurl=http://www.answers.com/topic/horse&h=133&w=200&sz=183&hl=en&start=16&tbnid=PeAihaF3A4O8kM:&tbnh=69&tbnw=104&prev=/images%3Fq%3Dhorse%2Bgallop%26gbv%3D2%26hl%3Denhttp://www.pakdef.info/pakmilitary/army/siachen/siachen8.jpghttp://images.google.com/imgres?imgurl=http://www.abrsm.org/images/general/hands_playing_piano.jpg&imgrefurl=http://www.abrsm.org/%3Fpage%3Dexams/choralEnsembles/primary.html&h=179&w=272&sz=10&hl=en&start=11&tbnid=HuR3brwCymMe6M:&tbnh=74&tbnw=113&prev=/images%3Fq%3Dplaying%2Bpiano%26gbv%3D2%26hl%3Den

Forward dynamics simulation

CNSactivationdynamics

muscletendon

dynamics

musculo-skeletalmodel

=M []-1

equationsof motion

u a FM

,

e(t) a(t) F(t) (t)

,, &&&

Simulation of OA gaitMuscle-actuated forward dynamic simulationEstimate of muscle forces responsible for observed movementEnables study of muscle coordination patternsAsymmetry in observed movement and underlying muscle control

www.simtk.org

Simulation results

Predicted reduction in quadriceps excitation and forceon more involved side.

Joint contact force

Inverse dynamics(F 100% BW)

Forward dynamics(F 200% BW)

From simulations

Estimates of muscle forces and joint contact forcePredict muscle coordination patternsHighlight muscle compensatory strategies

Experimental design

ImagingCartilageMappingGait analysis

MusculoskeletalSimulation

JOINT CONTACT FORCES CARTILAGE GEOMETRY

Static weight-bearing MRI

Upright

Tilt 45Knee 0

Tilt 45Knee 15

Tilt 45Knee 30

Image segmentation,cartilage mapping

tibio-femoral kinematics

Fonar upright open-MRI

Results Healthy knees

Cartilage centroid location moves distally with knee flexion

Results OA knees

Cartilage contact area and centroid location depends on OA severity

From imaging studies

Novel weight-bearing MRICartilage mapping illustrates loss of cartilage area and abnormal contact patternsIncreased tibio-femoral translations

Experimental design

ImagingCartilageMappingGait analysis

MusculoskeletalSimulation

JOINT CONTACT FORCES CARTILAGE GEOMETRY

Summary

Abnormal loading patterns for OA kneesAbnormal cartilage geometryKnee forces and functions

Depend on muscle coordinationImplications for other joints too!

Muscle coordination patterns can be modified

Research questions

Do abnormal forces lead to abnormal cartilage geometry?Are compensatory strategies beneficial or detrimental to OA progression?Do OA copers and non-copers exist?Can non-surgical interventions help?

Longitudinal study of OA progression

OA research at UDMulti-disciplinary study funded by NIH to address the mechanisms of OA prevention, progression and treatmentInvestigators from mechanical engineering, physical therapy, biology, health and exercise scienceUnique focus on mentoring women in science and engineering

OA research at UDPerlecan and Heparanase in Cartilage Growth and Healing(PI: Cindy Farach-Carson)

Solute Transport in the Subchondral Bone Plate of Osteoarthritic Joints (PI: Liyun Wang)

Risk Factors for Progression of Knee OA(PI: Jill Higginson)

Joint Loading and the Progression of Osteoarthritisfollowing Total Knee Arthroplasty (PI: Lynn Snyder-Mackler)

Knee Stiffness, Proprioception and Instability affect Knee Controlin OA (PI: Katy Rudolph)

AcknowledgementsNeuromuscular Biomechanics Laboratory

Joseph Zeni, Jr. Andy KubinskiMing Xiao Shridhar ShahChris Henderson Ben Roewer

CollaboratorsPeter Barrance, PhD

MentorsThomas Buchanan, PhDLynn Snyder-Mackler, PT, PhD

Research subjects!Martha Callahan

FundingNIH 2P20-RR16458

Biomechanics of Osteoarthritis:Analyzing knee forces and functionsArthritis and AmericansOsteoarthritis (OA)Knee osteoarthritisImplications of OARisk factorsPathomechanicsPathomechanicsMotivationOutlineExperimental designSubject recruitmentGait analysisGait analysisQuadriceps avoidance?Quadriceps avoidance!Total support momentTotal support momentResponse to challengeResponse to challengeFrom gait analysisExperimental designMusculoskeletal SimulationGeneration of movementForward dynamics simulationSimulation of OA gaitSimulation resultsJoint contact forceFrom simulationsExperimental designStatic weight-bearing MRIResults Healthy kneesResults OA kneesFrom imaging studiesExperimental designSummaryResearch questionsOA research at UDOA research at UDAcknowledgements