Harvard Human Anatomy - Joints

Joints (Articulations)

The unions between two or more bones or cartilages.

Abduction

Type of motion that occurs when a limb or limb segment moves away from the body midline.

Adduction

Type of motion that occurs when a limb or limb segment moves toward the body midline.

Bone congruence

The degree to which bone surfaces at joints are in contact.

Cartilage

A flexible connective tissue found in many areas in the human body.

Extension

Occurs when the angle between the bones meeting at a joint increases (becomes more obtuse).

Flexion

Occurs when the angle between the bones meeting at a joint decreases (becomes more acute).

Fibrous connective tissue

Unites bones meeting at fibrous joints and fills the spaces between them.

External rotation

Occurs when a limb or limb segment turns around its longitudinal axis away from the midline.

Internal rotation

Occurs when a limb or limb segment turns around its longitudinal axis toward the midline.

Synovial joints

Joints characterized by capsules surrounding articulating surfaces and lubricating fluid within those capsules. Their motion is determined by the shapes of the bone articular ends meeting at the joint and the ligaments and other structures limiting motion.

Ball and socket joint

A type of synovial joint permitting motion in three axes.

Condyloid joint

A type of synovial joint.

Hinge joint

A type of synovial joint permitting motion in one axis (flexion and extension).

Pivot joint

A type of synovial joint.

Plane joint

A type of synovial joint permitting the gliding of structures.

Saddle joint

A type of synovial joint.