Joint Terms


Abduction: Movement of a limb bone away from the median plane.


Adduction: Movement of a limb bone toward the median plane.


Amphiarthrosis: A slightly movable joint.


Ball and socket joint: A multiaxial synovial joint in which the hemispherical end of one bone fits into the corresponding cuplike cavity in the other bone, allowing motion in all planes.


Bursa: A closed sac lined with synovial membrane and filled with synovial fluid that reduces friction in a synovial joint, and is often found over an exposed body part.


Cartilaginous joint: An articulation in which the bones are joined together by cartilage, lacks a joint cavity, and almost no motion is possible; types are synchondroses, and symphyses.


Circumduction: Movement of a limb bone in a circular direction so that it describes a cone in the air.


Condyloid joint: A biaxial synovial joint in which the joint surfaces are ellipsoidal, allowing two axes of motion at right angles to each other. Also called condylar joint, or ellipsoid joint.


Depression: Movement of a bone inferiorly.


Diarthrosis: A freely movable joint.


Dorsiflexion: Upward movement of the foot that decreases the angle between the top of the foot (dorsal surface) and the anterior surface of the tibia, causing the toes to point superiorly.


Elevation: Movement of a bone superiorly.


Eversion: Turning the sole of the foot at the ankle joint to face laterally, and the great toe points inferiorly.


Extension: Movement at a joint which increases the angle between the articulating bones.


Fibrous joint: An articulation in which the bones are joined together by dense fibrous connective tissue, lack a joint cavity, and almost no motion is possible; types are sutures, syndesmoses, and gomphoses.


Flexion: Movement at a joint which decreases the angle between the articulating bones.


Functional classification of joints: Based on the amount of movement allowed; all joints are either synarthroses, amphiarthroses, or diarthroses.


Gliding joint: A nonaxial synovial joint in which the articulating surfaces are flat, which permits only side-to-side and back-and-forth movements.


Gomphosis: A fibrous joint in which a tooth articulates with its bony alveolar socket.


Hinge joint: A uniaxial synovial joint in which the convex end of one bone fits into the corresponding concave end of the other bone, which allows motion in one plane only like a door on its hinges.


Hyperextension: Movement at a joint to produce excessive extension, which increases the angle between the articulating bones beyond the normal range of motion.


Inversion: Turning the sole of the foot at the ankle joint to face medially, and the great toe points superiorly.


Opposition: Movement of the thumb so that it touches the tips of the other fingers


Osteoarthritis: A common chronic, "wear and tear" arthritis, which is the result of erosion of articular cartilage and hypertrophy of bone at the margins, accompanied by pain and loss of function; mainly affects weight-bearing joints and is more common in older people.


Pivot joint: An uniaxial synovial joint in which the cylindrical end of one bone fits into a corresponding cavity on the other bone, allowing rotational motion around the long axis.


Plane joint: A nonaxial synovial joint in which the opposing surfaces are nearly planar, and there is only a slight, gliding motion.


Plantar flexion: Downward movement of the foot that decreases the angle between the sole of the foot (plantar surface) and the posterior side of the tibia, causing the toes to point inferiorly.


Pronation: Rotating the arm medially so that the palm faces posteriorly or inferiorly, and the radius crosses diagonally over the ulna.


Protraction: Movement of the mandible into a position anterior to normal.


Retraction: Movement of the mandible into a position posterior to normal


Rheumatoid arthritis: A chronic and progressive inflammatory disorder of the joints that is an autoimmune disease which systematically destroys joints, leading to deformities and disability.


Rotation: Turning movement of a bone around its own long axis.


Saddle joint: A biaxial synovial joint in which double motion is allowed by the opposition of two surfaces, each of which is concave in one direction and convex in the other.


Structural classification of joints: Based on the material binding the bones together, and whether or not a joint cavity is present; all joints are either fibrous, cartilaginous, or synovial joints.


Supination: Rotating movement of the forearm laterally so that the palm faces anteriorly or superiorly.


Suture: A fibrous joint between two bones of the skull in which the bone edges interlock, and the junction is filled by very short fibers in a fibrous membrane that is continuous with the periosteum.


Symphysis: A cartilaginous joint in which two bones are united by fibrocartilage.


Synarthrosis: An immovable joint.


Synchondrosis: A cartilaginous joint in which two bones are united by hyaline cartilage.


Syndesmosis: A fibrous joint in which the opposing surfaces are relatively far apart and united by ligaments.


Synovial joint: An articulation in which the opposing bony surfaces are covered with a layer of articular cartilage within a joint cavity that contains synovial fluid, is lined with synovial membrane, and is reinforced by a fibrous capsule and ligaments.


Tendon sheath: An elongated bursa that wraps completely around a tendon, and is often found where a tendon passes over a bone.