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The knee joint is one of the most complicated joints in the human body. Fundamental knowledge about kinematics is essentially important in order to design knee prostheses which are functionally similar to the knee joint. In addition, the prosthesis should carry out similar kinematics, since only the geometrical resemblance is insufficient. As an initial step, an experimental apparatus, a test protocol and an evaluation method were developed which allows the investigation of the human knee joint kinematics. Based on the results of multiple experiments, a reference function was determined, which provides guidance on how the flexionrotation function in the human knee joint can be described. The function also provides reference about the kinematics which should be defined in the design of prostheses, and to what extent does an arbitrary knee prosthesis follows the required kinematics. The definition of knee rotation is reported in this article.

ABSTRACT:The available analytical models for calculating knee patellofemoral forces are limited to the standard squat motion when the center of gravity is fixed horizontally. In this paper, an analytical model is presented to calculate accurately patellofemoral forces by taking into account the change in position of the trunk's center of gravity under deep squat (non-standard squatting). The accuracy of the derived model is validated through comparisons with results of the inverse dynamics technique. Keywords:Patellofemoral forces, analytical model, modified squat, knee. RESUMEN:Los modelos analíticos disponibles para calcular las fuerzas patelofemorales de la rodilla están limitados al movimiento estándar de cuclillas cuando el centro de gravedad es fijo horizontalmente. En este artículo se presenta un modelo para calcular con exactitud las fuerzas patelofemorales, teniendo en cuenta el cambio de posición del centro de gravedad del tronco durante una sentadilla profunda (posición de sentadilla modificada). Se valida la exactitud del modelo desarrollado mediante comparaciones con resultados de la técnica de dinámica inversa.Palabras Clave: Fuerzas patelofemorales, modelo analítico, sentadilla modificada, rodilla.

During prosthesis implantation, the surgeon can choose from replacements of a wide variety of manufacturers and sizes. So far, no specific coefficient has been introduced that determines the suitability, or goodness of these prostheses. In this paper an apparatus is presented for the qualification of knee prostheses. This apparatus is able to measure the rotation of any prosthesis, therefore the obtained results can be compared with the measured values on human cadaver knees. The prostheses are classified by the rate of their conformity. In addition, the first experimental results are reported as well.

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