Fibrous Joint (Synarthrosis)

• Joint or articulation is formed by the union of two or more bones or cartilages.
• Joints are classified based on the nature of the uniting medium.

Fibrous Joint (Synarthrosis)

• These are nonmovable joints.
• Fibrocartilage is located between two adjacent bones.
• The uniting medium is fibrous tissue (collagen fibres).
• There is no joint cavity.
• Fibrous joints are immovable or fixed and are mostly temporary.
• Connective tissue joints (Syndesmoses) are a classification of fibrous joints, where the fibrous tissue can be elastic, white, or a mixture (connective tissue ligaments).
• An example is the tibiofibular joint.

Suture (Suturae)

• Suture joints are composed of four types.
• Serrata sutures: The edges of bones are irregular and interlocking with each other, examples include interfrontal and interparietal sutures
• Squamous sutures: The edges of bones are overlapped on each other which allow some movements to absorb shock, for example the temporo-parietal suture.
• Foliate suture: The edge of a bone fits in a recess or fissure of the adjacent bone, which is desirable in situations that require stability, for example the zygomaticomaxillary suture.
• Flat Suture: The edges of the bones are plane or slightly roughened, for example the internasal suture.

Impaction (Gomphoses)

• Gomphoses are joints between the teeth and the sockets (alveoli) of the mandible and maxillae.
• The connective tissue bundles between the teeth and their sockets are called periodontal ligaments, and they allow a slight amount of movement for the teeth during mastication.

Cartilaginous Joint (Amphiarthrosis):

• These are slightly movable joints.
• They are formed when two or more adjacent bones are united by a cartilaginous tissue.
• Bones are united by hyaline or fibrocartilage and are not highly movable.
• There is no joint cavity.
• Joints can be either synchondroses (containing hyaline cartilage) or symphysis (containing fibrocartilage).
• Symphyses are located along the midline of the body.

Primary Cartilaginous Joint or Synchondroses

• The bones are united by a plate or bar of hyaline cartilage.
• The unit medium is hyaline cartilage.
• Most are temporary
• They are fixed joints.
• An example is the articulation between the bony and cartilaginous parts of the ribs (costochondral junction).

Secondary Cartilaginous Joint or Symphysis

• Located along the midline of the body.
• Gives a small amount of movement.
• The uniting media is fibrocartilage.
• Examples include the mandibular and pelvic symphysis, and between the bodies of vertebrae.

Synovial Joint (Diarthrosis)

• These are freely movable joints.
• Formed when the articulation between two skeletal structures contains a gap.
• The gap or joint cavity is filled with joint fluid or synovia.
• Synovial joints are also called true joints.

Movements

• Flexion: decrease in the angle occurring in a sagittal plane, for example the shoulder joint.
• Extension: increase in the angle of bones occurring in a sagittal plane, for example the shoulder joint.
• Abduction (of limb): movement takes place away from the midline of the body in the coronal plane, for example the hip joint.
• Adduction (of limb): movement of a bone toward the midline of the body in the coronal plane, for example the hip joint.
• Rotation: movement of a bone around its longitudinal axis.
• Pronation: is a medial rotation of the forearm.
• Supination: is a lateral rotation of the forearm.

Movement of Temporomandibular Joint

• Protraction: movement of the temporomandibular forward.
• Retraction: movement of the temporomandibular backward.
• Elevation: movement of a body of mandible superiorly.
• Depression: movement of a body of mandible inferiorly.
• Rotation (side to side): also occurs, as in chewing.