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Joint

This article deals with anatomical joints. For information about joints in the context of cannabis, try: Spliff.

A joint in the human body (and other animals) is the area where two bones interact, about which a movement can be formed.

There are many joints in the human body, but they can be divided into different groups.

Table of contents

Synovial Joints The ends of each bone are covered in smooth articular cartilage, they are also lubricated with synovial fluid, this reduces friction and enables smooth movements to be produced.

The whole joint is contained in the joint capsule, which consists of a tough outer layer which helps to stabilise the joint, and a synovial membrane which produces synovial fluid.

Most of the joints that provide a lot of movement are synovial joints.

Synovial joints can be further grouped by their shape, which controls the movement they allow:

Hinge Joints

Such as the elbow[?] (between the humerus and the ulna). These joints act just like the hinge on a door, allowing flexion and extension in just one plane.

Ball and Socket Joint

Such as the hip joint[?]. These allow a wide arrange of movement.

Condyloid (or Ellipsoid) Joints

Such as the knee. When the knee is extended there is no rotation, when it is flexed some rotation is possible. A condyloid joint is where two bones fit together with an odd shape (e.g. an ellipse), and one bone is concave, the other convex.

Pivot Joints

Such as the elbow[?] (between the radius and the ulna). This is where one bone rotates about another.

Saddle Joints

Such as at the thumb (between the metacarpal[?] and carpal). Named so because of their shape, saddle joints, allow movement in a variety of directions.

Gliding Joints

Such as in the carpals of the wrist. These joints allow a wide variety of movement, but not much distance.

Cartilaginous Joints Unlike synovial joints these do not allow much movement. An example of this joint is the pubic symphysis[?].

Fibrous Joints These are not designed to allow any movement. The sutures in the skull are an example.



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