Definition: The bones are connected together by methods of fibrous, cartilaginous or tissues that are osseous various parts  of their particular surface. The connection is called joint or articulation.

1. The classification of articulations
i) Synarthrosis (immovable joints, direct joint)
Definition: two or even more separated bones are directly connected by stringy , cartilaginous or osseous tissues.

Fibrous joints:
a. sutures: skull
b. syndesmoses: ligmentum flava lig that is(yellow  tibiofibular joint
c. Gomphosis

a. synchondrosis: between sternum and 1st costal cartilage
b. symphyses :     pubic symphysis



ii) Diarthrosis (movable articulations, synovial joints)
Meaning: the bones tend to be connected by the capsule that is joint ligaments.

A- The fundamental (basical ) structures of synovial joint
1. The surface that is articular which will be part  of surface of bone covered by  hyaline cartilage.
2. The articular capsule: it appears like an abnormal sac, connects the periphery of the articular area and adjacent surface. Articular capsule include two parts: outer covering( fibrous layer ) and inner layer( synovial layer—produce synovial substance)
3. The articular cavity: it is really a closed area enclosed by  the synovial membrane layer and  the articular cartilage.

B. The accessory structures for the joints that are synovial
1. The ligment:
intracapsular lig: it is actually inside the shared , in the middle of synovial membrane
extracapsular lig: which is outside the pill
2. The disc that is articularor cartilage): it’s fibrocartilaginous, and divides the articular cavity    partially or completely into 2 parts.
3. The articular lip (labrum): this is  a fibrocartilaginous ring, which can deepen the surface that is articular


C. The activity of joint

1. Flexion and extension: they are performed in the coronal axis. Flexion makes the angle between the adjacent limbs decrease; extension increase the position.
2. Adduction and abduction: which are performed in sagittal axis. Adduction implies the action toward the midline of the  body; abduction suggests the movement aside through  the midline.
3. Pronation and supination: in standard position that is anatomical the pronation indicates the palm is turned backwards; the supination means the hand is switched forward.
4. Rotation: the movement is carried out in the straight axis. A bone is moving around the axis that is vertical.
5. Circumduction: while the proximal end of a bone tissue remains stable that is relative the distal end movements in a circle.