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From Wikipedia, the free encyclopedia

A Synovial joint, also known as a diarthrosis, is the most common and most movable type of joint in the body of a mammal. As with most other joints, synovial joints achieve movement at the point of contact of the articulating bones.

Structural and functional differences distinguish synovial joints from cartilaginous joints (synchondroses and symphyses) and fibrous joints (sutures, gomphoses, and syndesmoses). The main structural differences between synovial and fibrous joints is the existence of capsules surrounding the articulating surfaces of a synovial joint and the presence of lubricating synovial fluid within that capsule (synovial cavity).

Contents

Structure

Nerve Supply of Synovial Joint

It is derived from the nerve supply of muscles acting on the joint.

Blood Supply of Synovial Joint

From the arteries sharing in the anastomosis around the joint.

Movements possible

The movements possible with synovial joints are:

  • Abduction: movement away from the mid-line of the body.
  • Adduction: movement towards the mid-line of the body.
  • Extension: straightening limbs at a joint.
  • Flexion: bending the limbs at a joint.
  • Rotation: a circular movement around a fixed point.

Types

There are six types of synovial joints. Some are relatively immobile, but are more stable. Others have multiple degrees of freedom, but at the expense of greater risk of injury. In ascending order of mobility, they are:[1]

Name Example Description
Gliding joints (or planar joints) the carpals of the wrist, acromioclavicular joint These joints allow only gliding or sliding movements.
Hinge joints the elbow (between the humerus and the ulna)| These joints act like a door hinge, allowing flexion and extension in just one plane.
Joint between the atlas and axis neck bones, proximal radioulnar joint & distal radioulnar joint This is where one bone rotates about another.
Condyloid joints (or ellipsoidal joints) the wrist joint (radiocarpal joint) 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. Some classifications make a distinction between condyloid and ellipsoid joints.
Saddle joints the thumb (between the metacarpal and carpal) , sternoclavicular joint Saddle joints, which resemble a saddle, permit the same movements as the condyloid joints.
Ball and socket joints the shoulder(glenohumeral), and hip joints These allow a wide range of movement.

| compound joints | the kneejoint | condylar joint(condyles of femur join with condyles of tibia) and saddle joint(lower end of femur joins with patela).

Factors Influencing Joint Stability

References

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