Research Papers

Importance of Patella, Quadriceps Forces, and Depthwise Cartilage Structure on Knee Joint Motion and Cartilage Response During Gait

[+] Author and Article Information
K. S. Halonen

Department of Applied Physics,
University of Eastern Finland,
POB 1627,
Kuopio FI-70211, Finland
e-mail: kimmo.halonen@uef.fi

M. E. Mononen

Department of Applied Physics,
University of Eastern Finland,
POB 1627,
Kuopio FI-70211, Finland

J. S. Jurvelin, J. Töyräs, R. K. Korhonen

Department of Applied Physics,
University of Eastern Finland,
POB 1627,
Kuopio FI-70211, Finland;
Diagnostic Imaging Centre,
Kuopio University Hospital,
POB 100,
Kuopio FI-70029, Finland

A. Kłodowski

Laboratory of Machine Design,
Lappeenranta University of Technology,
Lappeenranta 53850, Finland

J.-P. Kulmala

Department of Biology of Physical Activity,
University of Jyväskylä,
Jyväskylä 40014, Finland

1Corresponding author.

Manuscript received July 15, 2015; final manuscript received April 26, 2016; published online June 7, 2016. Assoc. Editor: Tammy L. Haut Donahue.

J Biomech Eng 138(7), 071002 (Jun 07, 2016) (11 pages) Paper No: BIO-15-1348; doi: 10.1115/1.4033516 History: Received July 15, 2015; Revised April 26, 2016

In finite-element (FE) models of the knee joint, patella is often omitted. We investigated the importance of patella and quadriceps forces on the knee joint motion by creating an FE model of the subject's knee. In addition, depthwise strains and stresses in patellar cartilage with different tissue properties were determined. An FE model was created from subject's magnetic resonance images. Knee rotations, moments, and translational forces during gait were recorded in a motion laboratory and used as an input for the model. Three material models were implemented into the patellar cartilage: (1) homogeneous model, (2) inhomogeneous (arcadelike fibrils), and (3) random fibrils at the superficial zone, mimicking early stages of osteoarthritis (OA). Implementation of patella and quadriceps forces into the model substantially reduced the internal–external femoral rotations (versus without patella). The simulated rotations in the model with the patella matched the measured rotations at its best. In the inhomogeneous model, maximum principal stresses increased substantially in the middle zone of the cartilage. The early OA model showed increased compressive strains in the superficial and middle zones of the cartilage and decreased stresses and fibril strains especially in the middle zone. The results suggest that patella and quadriceps forces should be included in moment- and force-driven FE knee joint models. The results indicate that the middle zone has a major role in resisting shear forces in the patellar cartilage. Also, early degenerative changes in the collagen network substantially affect the cartilage depthwise response in the patella during walking.

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Fig. 2

FE model inputs, acquired from the subject's motion analysis. (a) Implemented moments and rotations. Extension–flexion input was implemented as rotation, while varus–valgus and internal–external inputs were implemented as moments. (b) Implemented total quadriceps force and its anterior–posterior and distal–proximal components. (c) Implemented translational forces.

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Fig. 3

Simulated muscle activations from multibody modeling and experimental EMG for vastus lateralis, vastus medialis, biceps femoris, and gastrocnemius medialis. Experimental EMG data and simulated activations of each muscle are normalized to the peak value of the activation during the stance phase of gait.

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Fig. 4

(a) Model geometry. The reference point (through which forces, moments, and extension–flexion rotation are implemented) is coupled to the femoral cartilage–bone interface. (b) Implementation of depthwise collagen fibril orientation in all the three models and the superficial primary fibril orientation (i.e., split-line pattern).

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Fig. 5

Femoral rotations and reaction forces in tibial and patellar cartilages during gait cycle: (a) extension–flexion rotation. All the models are identical due to the input, (b) internal–external rotation, (c) varus–valgus rotation, (d) reaction forces in the lateral tibial condyle, (e) reaction forces in the medial tibial condyle, and (f) reaction forces in the patellar cartilage.

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Fig. 6

Comparison between homogeneous, inhomogeneous, and osteoarthritic patellar cartilage models. Posterior view and axial view with femoral cartilage: (a)–(c) homogeneous patellar cartilage, (d)–(f) inhomogeneous patellar cartilage, and (g)–(i) osteoarthritic patellar cartilage.

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Fig. 7

Average fibril strains in the patellar cartilage as a function of time at different depths: (a) element layer 1 (superficial zone), (b) element layer 2 (middle zone), (c) element layer 3 (deep zone), and (d) element layer 4 (deep zone)

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Fig. 8

Average compressive strains in the patellar cartilage as a function of time at different depths: (a) element layer 1 (superficial zone), (b) element layer 2 (middle zone), (c) element layer 3 (deep zone), and (d) element layer 4 (deep zone)

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Fig. 9

Average maximum principal stresses in the patellar cartilage as a function of time at different depths: (a) element layer 1 (superficial zone), (b) element layer 2 (middle zone), (c) element layer 3 (deep zone), and (d) element layer 4 (deep zone)



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