The Effect of Unstable Shoes on Knee Joint Reaction Forces

<strong>The</strong> <strong>Effect</strong> <strong>of</strong> <strong>Unstable</strong> <strong>Shoes</strong> onKnee Joint Contact ForceJake GardnerBME 599 PresentationApril 26, 2012

Introduction• <strong>Unstable</strong> shoes have gained recent popularity• Claims for the efficacy <strong>of</strong> the shoe include:– Increased muscle tone– Improved posture– Reduce pressure on feet– Potential benefit for diseased populations such asknee osteoarthritis (OA)

Introduction• Previously, our lab has done gait analyses ontwo different unstable shoes1 st Generation 2 nd Generation

Purpose and Hypothesis• Determine the knee joint contact forces inhealthy individuals while walking with anunstable shoe compared to a control shoe• Hypothesis: Wearing the unstable shoe willdecrease the vertical knee joint contact force

Experimental DesignExperimentalData• Walk acrossforce plate incontrol andtest shoes• 3D MotionCapture• EMGVisual 3D• Process data• Performinversedynamics• Export motiontrials toOpenSimOpenSim• Scale V3Dmodel toOpenSimmodel• Perform RRA• Perform CMC•Calc JRF

Methods: Data Collection• 14 healthy men– Age: 45.4 ± 8.4 yrs– Height: 1.82 ± 0.07 m– Weight: 83.2 ± 13.5 kg• Walked at 1.3 m/s across a force plate– In control and test shoes• 3D motion capture with reflective markers– Bilateral marker set

Methods: OpenSim Processing• Exported walking to use in OpenSim• Scaled V3D model to OpenSim model• Performed residual reduction analysis (RRA)• Performed computed muscle control (CMC)• Performed JRFcalculation

CMC1500100050000 20 40 60 80 10015001000500EMG3002502001501005000 20 40 60 80 10010864200 20 40 60 80 1001500100050002001501000500 20 40 60 80 10000 20 40 60 80 10000 20 40 60 80 100150080100060405002000 20 40 60 80 10000 20 40 60 80 100

Results: Knee Contact ForceWhy is the 2 nd peak larger?Control Shoe<strong>Unstable</strong> Shoe6655Force (BW)4324321100 10 20 30 40 50 60 70 80 90 10000 10 20 30 40 50 60 70 80 90 100Stance (%)

Results: Force Comparisons654Force (BW)32KCFGRFJRF100 10 20 30 40 50 60 70 80 90 100% Stance

Results

200150Residuals(Force FY)100500-50-100-1500 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9Time (s)

Results: KCF Comparisons (Single trial)765Force (BW)43Single Support~ 0.6 BW21Stance00 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9Time (s)

Results: Left Knee Contact Force43.53Force (BW)2.521.510.53 BW00.6 0.7 0.8 0.9 1 1.1 1.2 1.3Time (s)

Discussion: D’Lima 2006Real Science

Discussion: Richards and Higginson (2010)~ 4.5 BW• Used OpenSim methods similar to this study•Participants between the ages <strong>of</strong> 40 and 85• Walked at a self selected pace (healthy 1.3 m/s; moderate 1.2 m/s)

Sasaki and Neptune 2010~ 2.7 BW• Walking speed <strong>of</strong> 1.2 m/s• Used simulated annealing to minimize cost function• <strong>The</strong>ir model had less muscles than the OpenSim model

Results: Muscle activity comparisonCMCEMGSasaki 20102000400100020000 50 10000 50 1001500100050000 50 1001500500-500 0 50 100150010502001000800 50 1000 50 10050030-5000 50 100 -200 50 100

Conclusion (If these results are accurate)• 1 st peak knee contact force decreased by 0.5 – 1 BW bywearing unstable shoes– Possible benefit for OA• 3 force plates needed for walking– Need GRF in double support• KCF much greater than JRF calculated by inversedynamics• Large residuals ≠ large KCF• Future research– Other activities: Stair walking, cycling, elliptical machine– Incorporate contact surfaces to determine loads on medialand lateral compartments

References• D’Lima DD, Patil S, Steklov N, et al. 2006. Tibial forces measured in vivoafter total knee arthroplasty. J Arthroplasty. 21(2),255-261.• Richards C, Higginson JS. 2010. Knee contact forces in subjects withsymmetrical OA grades: differences between OA severities. J Biomech.43,2595-2600.• Sasaki K, Neptune RR. 2010. Individual muscle contributions to the axialnee joint contact force during normal walking. J Biomech. 43,2780-2784.