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.

.

There are a number of movements produced by muscle contraction that have specific names in anatomical terminology.

• Flexion: it is the approximation of two surfaces or the making of an angle.
• Extension: the return back from flexion and increasing the angle between body parts the straightening.

• Abduction: moving away from the central axis.
• Adduction: moving towards the central axis.
• Medial rotation: rotation towards the median plane.
• Lateral rotation: rotation away from the median plane.

• Supination: lateral rotation of the forearm so that the palm faces anteriorly.
• Pronation: medial rotation of the forearm so that the palm faces posteriorly.
• Inversion: the sole faces in a medial direction.
• Eversion: the sole faces in a lateral direction.

• Circumduction: It is the combination of flexion, extension,abduction and adduction that produces a circular motion.

.

For descriptive purposes, it has been agreed to consider the subject standing upright, face looking forward and arms straight by the side with the palms facing forwards. This is called the anatomical position.

Anatomical planes:

• Median plane: vertical line that passes through the body longitudinally.
• Sagittal plane: vertical planes passing through the body parallel to the median plane. E.g. such as a sagittal plane through the midpoint of the clavicle.
• Coronal plane: vertical lines which passes at right angles to the median or sagittal planes and it divides the body into anterior and posterior parts.
• Transverse plane: horizontal plane which passes through the body at a right angle to the median, sagittal or coronal plane. Divides the body into upper and lower parts.

Terms of positions

• Medial: Nearer to the median plane of the body.
• Lateral: Away from the median plane.
• Superior: Toward the head end (upper) part of the body.
• Inferior: Toward the lower part of the body.

• Proximal: Close to the origin of the body part or the point of attachment of a limb to the body trunk.

• Distal: Farther from the origin of a body part or the point of attachment of a limb to the body trunk

Superficial (External) : toward or at the surface or the center of an organ or a cavity.
Deep (Internal): away from the body surface or the center.

.