Classification of Joints

A joint is the site were two or more bones come together and form an articulation, whether there is movement or not.

Fibrous joints:

- The articulating surfaces are joined by fibrous tissue.
- Very little movement is possible.
Example: Surfaces of the vault of the skull, inferior tibio-fibular joints.

Cartilaginous joints
A. Primary Cartilaginous: The bones are united by a plate of hyaline cartilage.

1. Between the Epiphysis and Diaphysis of a growing bone.
2. Between the first rib and the sternum.

B. Secondary Cartilaginous
The bones are united by a plate of fibrocartilage.
Their articulating surfaces are covered by a thin plate of hyaline cartilage.

(1) joints between the vertebral bodies.
(2) Symphysis pubis.

Synovial joints

- The articulating bones are covered by hyaline cartilage and separated by a joint cavity.
- It has a great degree of freedom of movement.
- The cavity is lined by synovial membrane.
- It is protected on the outside by a tough fibrous capsule.
- The synovial membrane produces a lubricating fluid (synovial fluid.

Types of synovial joints:
1. Plane: The articulating surfaces are flat and the bones slide on one another.
- E.G: Sternoclavicular and Acromioclavicular joints.
2. Hinge: It is a uni axial joint. E.G: Elbow, Knee and Ankle joints.
3. Pivot: A central bony pivot is surrounded by a bony ligamentous ring.
- E.G: Atlanto-axial, superior radioulnar.
4. Condyloid: Two convex articular surfaces articulate with two concave.
- E.G: Metacarpophalangeal (kunckle joints).
5. Saddle: The articulating surfaces are reciprocally concavoconvex.
- E.G: Carpometacarpal joint of the thumb.
6. Ellipsoid: The oval-shaped end of one bone fits into an oval-shaped cavity in another bone.
- E.G: Wrist joint.
7. Ball and Socket: A ball –shaped head of one bone fits into a socket like concavity of another.
- E.G: Shoulder and Hip.

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