Joints in Motion Study Guide (1.2.5–1.2.6)

Comprehensive vocabulary flashcards covering joint classifications, types of synovial joints, pairs of movement, cartilage varieties, range of motion measurement, knee ligaments, clinical stability tests, and rehabilitation exercises.

Hyoid bone

The only bone in the body that does not meet at least one other bone at a joint.

Synarthrosis

A functional classification for an immovable, rigid joint that allows no motion.

Amphiarthrosis

A functional classification for a slightly movable joint that allows limited motion.

Diarthrosis

A functional classification for a freely movable joint that allows a full range of motion.

Fibrous joint

A fixed joint made primarily of collagen where dense fibrous connective tissue holds bone margins together with minimal space and allows no movement.

Cartilaginous joint

A joint where bones are connected entirely by cartilage (hyaline or fibrocartilage), acting as a shock-absorbing cushion with limited motion.

Synovial joint

The most common and freely movable joint type in the body, characterized by an articular capsule with a synovial membrane, synovial fluid to reduce friction, and articular cartilage.

Ball-and-socket joint

A synovial joint type that allows backward, forward, sideways, and rotating movement, providing the greatest range of motion of any joint (e.g., shoulder, hip).

Hinge joint

A synovial joint that allows bending and straightening in a single plane, like a door hinge (e.g., elbow, knee).

Pivot joint

A synovial joint that allows limited rotation where one bone rotates around another (e.g., first two vertebrae of the neck, radius and ulna).

Saddle joint

A synovial joint that permits backward and forward and side-to-side motion, but no rotation (e.g., carpometacarpal joint at the base of the thumb).

Condyloid (ellipsoidal) joint

A synovial joint that allows back-and-forth movement in multiple directions without rotation (e.g., wrist where the radius meets the carpal bones).

Plane (gliding) joint

A synovial joint where flat bone surfaces slide across one another (e.g., between the carpal bones of the wrist, acromioclavicular joint of the shoulder).

Flexion

A movement that decreases the angle between two body parts at a joint (bending).

Extension

A movement that increases the angle between two body parts (straightening).

Hyperextension

Extending a joint past its normal straight position.

Plantar flexion

Pointing the foot and toes downward, away from the shin, like pressing a gas pedal.

Dorsiflexion

Pulling the foot and toes upward, toward the shin.

Abduction

Moving a body part away from the midline of the body.

Adduction

Moving a body part toward the midline of the body.

Rotation

Moving a body part around its own axis.

Circumduction

Moving a body part in a circular motion, combining flexion, extension, abduction, and adduction.

Depression

Moving a body part downward.

Elevation

Moving a body part upward.

Pronation

Turning the forearm so the palm faces downward or backward.

Supination

Turning the forearm so the palm faces upward or forward.

Articular (hyaline) cartilage

Cartilage covering the ends of bones (condyles) within synovial joints to cushion the joint, allow easy bending and straightening motions, and protect against weight-bearing stress.

Elastic cartilage

Flexible cartilage found in the ear, epiglottis, and upper respiratory tract that holds its shape while allowing bending, but does not cushion a joint between bones.

Fibrocartilage

Tough, compression-resistant cartilage found in the intervertebral discs of the spine and the pubic symphysis for locations needing extra shock absorption.

Range of motion (ROM)

How far a joint can move, measured in degrees with a goniometer (typical adult knee flexion is $135^\circ$).

Active ROM

Range of motion measured when the person moves the joint themselves.

Passive ROM

Range of motion measured when someone else moves the joint for the person.

Goniometer

An instrument used to measure joint range of motion in degrees, consisting of a body, a fulcrum, a stationary arm, and a moving arm.

Fulcrum (goniometer)

The pivot point of a goniometer that sits directly over the joint's axis.

Medial collateral ligament (MCL)

A knee ligament attaching the femur proximally to the tibia distally that protects the joint from collapsing inward or opening up under stress.

Anterior cruciate ligament (ACL)

A central knee stabilizer attaching from the posterolateral, inner side of the femur proximally to the tibia distally, preventing forward shin movement, controlling rotation, resisting hyperextension, and aiding position sense.

Lateral collateral ligament (LCL)

A knee ligament attaching the femur proximally to the head of the fibula distally that restrains varus stress, controls posterolateral rotation, maintains joint alignment, and acts as a secondary stabilizer.

Posterior cruciate ligament (PCL)

A knee ligament attaching from the anterolateral surface of the femur proximally to the posterior tibia distally that prevents backward shin movement, controls rotation, and provides strength.

Joint laxity

Excessive looseness in a joint, which indicates a positive result during clinical knee stability tests.

Anterior drawer test

A clinical test performed with the knee flexed at $90^\circ$ where the proximal tibia is pulled anteriorly to evaluate anterior tibial translation; a positive result shows the femur sliding significantly in the posterior direction.

Valgus stress test

A clinical test performed with the knee flexed at about $30^\circ$ with the femur held fixed and the tibia rotated laterally into a valgus position to directly test the medial collateral ligament (MCL) against inward forces.

Varus stress test

A clinical test performed with the knee flexed at $30^\circ$ with the femur held fixed and the tibia rotated medially into a varus position; a positive result shows the femur sliding significantly in the lateral direction.

Heel slides

A rehabilitation exercise performed by sliding the heel along the floor toward the glutes and slowly straightening it, restoring early knee flexion and extension without weight-bearing, twisting, or side-to-side stress.