Saddle joint
A saddle joint (the articulatio sellaris ) is a joint that allows movement in two mutually perpendicular axes and thus has two degrees of freedom . The directions of movement here are flexion / extension or abduction / adduction of the joint. Both joint surfaces are shaped like a riding saddle and the convexity of one joint surface corresponds to the concavity of the other and vice versa.
One example is the root joint of the human thumb ( thumb saddle joint , Articulatio carpometacarpalis pollicis ) between the large polygonal bone and the first metacarpal bone . By combining the movements in both main axes, it is possible to circle the thumb. The saddle joint on the thumb has no special facilities.
The joint between the two ossicles, the hammer ( malleus ) and the anvil ( incus ), the articulatio incudomallearis , is also a saddle joint.
History of the saddle joint
Up to 80% of women over the age of 40 are affected by rhizarthrosis . This is due to a growth disorder, which means that the saddle of the saddle joint in women is often inclined. The fact that rhizarthrosis is so common is related to the fact that the saddle joint in question - measured by the length of the history of human development - is relatively "young", namely eight million years. Only through this special joint did humans have the opportunity to hold objects properly and, for example, to play the flute . Due to its low age in terms of evolutionary biology , it is not yet perfectly developed and not as resilient as it would be desirable.
See also
literature
- Kurt Tittel: Descriptive and functional human anatomy . Elsevier, Urban & Fischer, 14th edition 2003, ISBN 3-437-46151-6 , p. 49.
Individual evidence
- ↑ Sebastian Knoppik: When the rider slips off the saddle. Hildesheim hand surgeon Rieck provides information about special forms of osteoarthritis at the Sarstedt patient forum. In: Leine Nachrichten issue 21/2016 from January 26th, 2016 (supplement of the Hannoversche Allgemeine Zeitung).