Mechanical Function of the Patella

Kaufer, Herbert

doi:10.2106/00004623-197153080-00007

Cited by 312 publications

(120 citation statements)

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“…Because the moment arm of the extensor mechanism is distributed both above and below the patella [18], the medial portion ofthe patellar tendon may effectively be sustaining more tension than its lateral portion. El Khoury et al [8] concluded that the most useful sign indicating the presence of chronic patellar tendinitis was focal enlargement of the proximal patellar tendon exceeding 7 mm in the anteropostenior dimension.…”

Section: Objectivementioning

confidence: 99%

Correlation of MR imaging and pathologic findings in athletes undergoing surgery for chronic patellar tendinitis.

Yu¹,

Popp²,

Kaeding³

et al. 1995

American Journal of Roentgenology

136

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Section: Objectivementioning

confidence: 99%

Correlation of MR imaging and pathologic findings in athletes undergoing surgery for chronic patellar tendinitis.

Yu¹,

Popp²,

Kaeding³

et al. 1995

American Journal of Roentgenology

136

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“…The main functions of the patella (knee-cap) are to im prove the efficiency of the extensor forces through the entire knee flexion range (Ahmed et a l, 1987;Kaufer, 1971), to centralize the forces of the different quadriceps muscle bellies and to provide a smooth sliding mecha nism for the quadriceps muscle with little friction due to its cartilage cover (Ficat, 1970). It also indirectly contrib utes to the global stability of the knee (Bonnel, 1988), Finally according to some authors (Fick, 1904;Freehafer, 1962) it provides the anterior aspect of the knee with a protecting shield.…”

Section: Introductionmentioning

confidence: 99%

The biomechanics of the human patella during passive knee flexion

Heegaard

Leyvraz

Curnier

et al. 1995

Journal of Biomechanics

166

119

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Abstract-The fundamental objectives of patello-femoral joint biomechanics include the determination of its kinematics and of its dynamics, as a function of given control parameters like knee flexion or applied muscle forces. On the one hand, patellar tracking provides quantitative information about the joint's stability under given loading conditions, whereas patellar force analyses can typically indicate pathological stress distributions asso ciated for instance with abnormal tracking, The determination of this information becomes especially relevant when facing the problem of evaluating surgical procedures in terms of standard (i.e. non-pathological) knee functionality. Classical examples of such procedures include total knee replacement (TKR) and elevation of the tibial tubercle (Maquet's procedure).Following this perspecti ve, the current study was oriented to ward an accurate and reliable determination of the human patella biomechanics during passive knee flexion. To this end, a comprehensive three-dimensional computer model, based on the finite element method, was developed for analyzing articular biomechanics. Unlike previously published studies on patello-femoral biomechanics, this model simultaneously computed the joint's kinematics, associated tendinous and ligamentous forces, articular contact pressures and stresses occurring in the joint during its motion. The components constituting the joint (i.e. bone, cartilage, tendons) were modeled using objective forms of non-linear elastic materials laws. A unilateral contact law allowing for large slip between the patella and the femur was implemented using an augmented Lagrangian formulation, Patellar kinematics computed for two knee specimens were close to equivalent experimental ones (average deviations below 0.5° for the rotations and below 0.5 mm for the translations) and provided validation of the model on a specimen by specimen basis. The ratio between the quadriceps pulling force and the patellar tendon force was less than unity throughout the considered knee flexion range (30-150°), with a minimum near 90° of flexion for both specimens. The contact patterns evolved from the distal part of the retropatellar articular surface to the proximal pole during progressive flexion. The lateral facet bore more pressure than the medial one, with corresponding higher stresses (hydrostatic) in the lateral compartment of the patella. The forces acting on the patella were part of the problem unknowns, thus leading to more realistic loadings for the stress analysis, which was especially important when considering the wide range of variations of the contact pressure acting on the patella during knee flexion.

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“…[1] It is the largest sesamoid bone [2] and its fracture accounts for approximately 1% of all fractures in adults. [3] Either a direct or indirect mechanism leads to the fractures of patella.…”

Section: Introductionmentioning

confidence: 99%