A saddle joint (sellar joint,
articulation by reciprocal reception) is a type of
synovial joint
A synovial joint, also known as diarthrosis, joins bones or cartilage with a fibrous joint capsule that is continuous with the periosteum of the joined bones, constitutes the outer boundary of a synovial cavity, and surrounds the bones' articulat ...
in which the opposing surfaces are reciprocally concave and convex. It is found in the
thumb
The thumb is the first digit of the hand, next to the index finger. When a person is standing in the medical anatomical position (where the palm is facing to the front), the thumb is the outermost digit. The Medical Latin English noun for thumb ...
, the
thorax
The thorax or chest is a part of the anatomy of humans, mammals, and other tetrapod animals located between the neck and the abdomen. In insects, crustaceans, and the extinct trilobites, the thorax is one of the three main divisions of the ...
, the
middle ear, and the
heel.
Structure
In a saddle joint, one bone surface is concave while another is convex.
This creates significant stability.
Movements
The movements of saddle joints are similar to those of the
condyloid joint and include
flexion,
extension,
adduction,
abduction
Abduction may refer to:
Media
Film and television
* "Abduction" (''The Outer Limits''), a 2001 television episode
* " Abduction" (''Death Note'') a Japanese animation television series
* " Abductions" (''Totally Spies!''), a 2002 episode of an ...
, and
circumduction.
However,
axial rotation is not allowed. Saddle joints are said to be biaxial, allowing movement in the sagittal and frontal planes.
Examples of saddle joints in the human body include the
carpometacarpal joint of the
thumb
The thumb is the first digit of the hand, next to the index finger. When a person is standing in the medical anatomical position (where the palm is facing to the front), the thumb is the outermost digit. The Medical Latin English noun for thumb ...
,
the
sternoclavicular joint of the
thorax
The thorax or chest is a part of the anatomy of humans, mammals, and other tetrapod animals located between the neck and the abdomen. In insects, crustaceans, and the extinct trilobites, the thorax is one of the three main divisions of the ...
, the
incudomalleolar joint of the
middle ear,
and the
calcaneocuboid joint of the
heel.
Name
The term "
saddle" arises because the concave-convex bone interaction is compared to a
horse rider riding a
horse, with both bone surfaces being saddle-shaped.
The saddle joint is also known as the sellar joint.
References
External links
Diagram at phschool.com
{{DEFAULTSORT:Saddle Joint
Joints