Final rotation
The final rotation in the knee joint is an involuntary movement that takes place passively with maximum knee extension. An external rotation of the lower leg or an internal rotation of the thigh by approx. 5 ° is described here. If the leg is unloaded, the tibia rotates more likely with a stable thigh bone . If the leg is loaded, the thighbone rotates with a stable shin.
The final rotation is brought about by the anterior cruciate ligament with the support of the iliotibial band . As a result of the final rotation, on the one hand the collateral ligaments are tightened and on the other hand the joint is physiologically minimally subluxed , so that the thighbone no longer lies optimally in its joint socket of the tibial plateau. This stabilizes the joint and prevents it from “slipping” unintentionally. In order to allow the knee to flex, the final rotation must first be canceled by pulling the popliteus muscle and the internal rotators of the lower leg (attachment to the pes anserinus : semitendinosus , sartorius and gracilis muscles ). The final rotation of the extension is the (reverse) initial rotation of the flexion.
The extent of the final rotation depends on the basic position of the leg bones in relation to one another. For most people it is around 5–10 degrees (see above). In people with knock knees ( genu valgum ) it is stronger in people with bow legs ( genu varum ) little or non-existent.
There are discussions about whether the final rotation takes place during "normal" walking. The knee is not fully extended when walking, but the final rotation starts at an extension angle of 20 ° –30 °.
In some sports in which the knee is consciously extended to the maximum (e.g. Tango ), the knee cannot be "entrotated" by the popliteus muscle , since the extended leg is part of the dance technique . This is why locomotion is initiated by a pronounced hip movement, which on the one hand shifts the body's center of gravity and thus causes the locomotion and on the other hand rotates the thighbone outwards on the shin and thus also eliminates the final rotation in the knee.
The anatomist Georg Hermann von Meyer was the first to describe this process in 1853 and published it in Müller's archive (p. 32 and 500).
Individual evidence
- ↑ a b Michael Jagodzinski, Niklaus Friederich, Werner Müller: The knee: form, function and ligamentous reconstructive surgery. Springer 2016, ISBN 978-3-642-45001-3 , pp. 38–43 ( online in the Google book search).
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↑ Source citation as in: Georg Hermann von Meyer: Statik und Mechanik des Menschen Fusses. Verlag Gustav Fischer, Jena 1886, p. 18. ( Online - Internet Archive )
- Hermann Meyer: Standing upright. (First contribution to the mechanics of the human skeleton). In: Johannes Müller : Archive for Anatomy, Physiology and Scientific Medicine. 1853, pp. 9-44. ( P. 32 online )
- Hermann Meyer: The mechanics of the knee joint. (Third contribution to the mechanics of the human skeleton). In: Johannes Müller: Archive for Anatomy, Physiology and Scientific Medicine. 1853, pp. 497-547. ( P. 500 online )