Chapter 8: Joints (Articulations)

Comprehensive vocabulary flashcards covering functional and structural joint classifications, synovial joint anatomy and movements, specific joint structures, and clinical implications from Chapter 8.

Joints (Articulations)

Sites where two or more bones meet; their primary functions are to give the skeleton mobility and hold it together.

Synarthroses

Immovable joints based on functional classification of movement.

Amphiarthroses

Slightly movable joints based on functional classification of movement.

Diarthroses

Freely movable joints based on functional classification of movement.

Fibrous Joints

Joints where bones are united by dense fibrous connective tissue without a joint cavity; most are immovable.

Sutures

Rigid, interlocking fibrous joints of the skull that allow for growth during youth and ossify and fuse into immovable joints in middle age to protect the brain.

Syndesmoses

Fibrous joints where bones are connected exclusively by ligaments or bands of fibrous tissue (e.g., the inferior tibiofibular joint or the interosseous membrane connecting the radius and ulna).

Gomphoses

Peg-in-socket fibrous joints that hold a tooth firmly in its socket.

Cartilaginous Joints

Joints where the articulating bones are united by cartilage; they lack a joint cavity and are not highly movable.

Synchondroses

Cartilaginous joints where a bar or plate of hyaline cartilage unites the bones, such as the cartilage of the first rib with the manubrium of the sternum.

Symphyses

Cartilaginous joints where fibrocartilage unites the bones, such as in intervertebral joints and the pubic symphysis.

Synovial Joints

Diarthrotic (freely movable) joints where the articulating bones are separated by a fluid-filled joint cavity; includes almost all limb joints.

Articular Cartilage

Smooth hyaline cartilage covering the opposing ends of bones in a synovial joint that absorbs compression and prevents bone ends from being crushed.

Joint (Synovial) Cavity

A potential space that contains a small amount of synovial fluid and is unique to synovial joints.

Articular (Joint) Capsule

A two-layered sleeve enclosing the joint cavity, composed of an external fibrous layer of dense irregular connective tissue and an inner synovial membrane of loose connective tissue that secretes synovial fluid.

Synovial Fluid

A viscous, slippery filtrate of plasma and hyaluronic acid that lubricates and nourishes articular cartilage and contains phagocytic cells to eliminate microbes and cellular debris.

Bursae

Fibrous sacs lined with synovial membrane and filled with synovial fluid that act as ball bearings to reduce friction where ligaments, muscles, skin, tendons, or bones rub together.

Tendon Sheaths

Elongated bursae that wrap completely around tendons subjected to friction to decrease wear and tear.

Articular Discs (Menisci)

Pads of fibrocartilage that separate articular surfaces to improve bone fit, enhance joint stability, and reduce wear and tear.

Muscle Tone

The most important factor determining synovial joint stability, acting by keeping tendons crossing the joint taut (extremely critical in the shoulder, knee, and arches of the foot).

Gliding Movements

Nonaxial movements occurring when flat or nearly flat surfaces of two bones slide across each other, such as in intercarpal and intertarsal joints.

Flexion

An angular movement that decreases the angle between two articulating bones, usually in the sagittal plane.

Extension

An angular movement that increases the angle between two articulating bones, usually in the sagittal plane.

Hyperextension

An angular movement that extends a joint beyond the anatomical position.

Abduction

An angular movement along the frontal plane that moves a limb away from the midline of the body.

Adduction

An angular movement along the frontal plane that moves a limb toward the midline of the body.

Circumduction

A compound movement involving flexion, abduction, extension, and adduction where a limb or finger describes a cone in space.

Rotation

The turning of a bone around its own longitudinal axis, directed either toward the midline (medial rotation) or away from it (lateral rotation).

Supination

Rotation of the forearm so that the palm faces anteriorly and the radius and ulna remain parallel.

Pronation

Rotation of the forearm so that the palm faces posteriorly and the radius rotates over the ulna.

Opposition

The specialized movement of the thumb that allows its tip to contact the tips of any of the other fingers on the same hand.

Dorsiflexion

Upward movement that lifts the superior surface of the foot toward the shin (as in standing on one's heel).

Plantar Flexion

Downward movement that moves the superior surface of the foot farther away from the shin (as in pointing one's toes).

Inversion

Special movement of the foot that turns the sole medially.

Eversion

Special movement of the foot that turns the sole laterally.

Elevation

Lifting a body part superiorly, such as closing the mouth or shrugging shoulders.

Depression

Moving an elevated body part inferiorly, such as opening the mouth.

Protraction

A nonangular anterior movement in the transverse plane that pushes the mandible forward.

Retraction

A posterior movement in the transverse plane that pulls the mandible back toward the neck.

Plane Joint

A synovial joint with flat articular surfaces that allows nonaxial gliding movements (e.g., intercarpal and intertarsal joints).

Hinge Joint

A uniaxial synovial joint in which a cylindrical projection fits into a trough-shaped surface, permitting flexion and extension only (e.g., elbow and interphalangeal joints).

Condylar Joint

A biaxial synovial joint featuring oval articular surfaces that allow flexion, extension, adduction, and abduction (e.g., metacarpophalangeal knuckle joints and wrist joints).

Saddle Joint

A biaxial synovial joint in which both articular surfaces have complementary concave and convex areas, permitting flexion, extension, abduction, and adduction (e.g., carpometacarpal joint of the thumb).

Ball-and-Socket Joint

A multiaxial synovial joint featuring a spherical head fitting into a cup-like socket, permitting movements in all planes including rotation (e.g., shoulder and hip joints).

Temporomandibular Joint (TMJ)

A synovial joint of the jaw that most commonly dislocates due to its shallow socket, almost always displacing anteriorly so the mouth remains open.

Glenohumeral Joint

The ball-and-socket shoulder joint where the hemispherical head of the humerus articulates with the shallow glenoid cavity of the scapula; the most freely moving joint in the body.

Sprain

An injury where the reinforcing ligaments of a joint are stretched or torn, healing very slowly because of poor vascularization.

Dislocation (Luxation)

An injury where articulating bones are forced out of alignment, typically caused by serious falls or contact sports, requiring reduction to treat.

Subluxation

A partial dislocation of a joint.

Bursitis

Inflammation of a bursa, usually caused by a blow or repetitive friction, treated with rest, ice, and anti-inflammatory medications.

Tendonitis

Inflammation of tendon sheaths, typically caused by overuse, presenting with symptoms and treatment similar to bursitis.

Arthritis

A broad category encompassing over 100 different inflammatory or degenerative joint diseases that cause pain, stiffness, and swelling.