Chapter 9: Joints - Human Anatomy & Physiology I

Vocabulary practice flashcards covering joint classifications, synovial joint anatomy, lever systems, biomechanical movements, major diarthroses, and joint disorders from Chapter 9 of Saladin's Anatomy & Physiology.

Joint (Articulation)

Any point where two bones meet, whether or not the bones are movable at that interface.

Arthrology

The science of joint structure, function, and dysfunction.

Kinesiology

The study of musculoskeletal movement.

Synostosis (Bony Joint)

An immobile joint formed when the gap between two bones ossifies and they become a single fused bone.

Synarthrosis (Fibrous Joint)

A joint at which adjacent bones are bound together by collagen fibers that emerge from one bone and penetrate into the other.

Suture

An immobile or slightly mobile fibrous joint whose short collagen fibers closely bind the bones of the skull together.

Serrate Suture

A suture characterized by interlocking wavy lines, such as coronal, sagittal, and lambdoid sutures.

Lap (Squamous) Suture

A suture where overlapping beveled edges meet, found between the temporal and parietal bones.

Plane (Butt) Suture

A suture formed by straight, non-overlapping abutting edges, seen between the palatine processes of the maxillae.

Gomphosis

A fibrous joint that attaches a tooth to its bone socket via the fibrous periodontal ligament.

Syndesmosis

A fibrous joint in which two bones are bound by relatively long collagen fibers, such as the interosseous membrane joining the radius and ulna.

Amphiarthrosis (Cartilaginous Joint)

A joint in which two bones are linked together by cartilage.

Synchondrosis

A cartilaginous joint in which the connecting material is hyaline cartilage, such as the epiphyseal plate or the attachment of rib 1 to the sternum.

Symphysis

A cartilaginous joint where two bones are joined by fibrocartilage, such as the pubic symphysis and intervertebral discs.

Diarthrosis (Synovial Joint)

A structurally complex joint in which two bones are separated by a fluid-filled joint cavity; most are freely mobile.

Articular Cartilage

A smooth layer of hyaline cartilage covering the facing surfaces of articulating bones.

Synovial Fluid

A slippery lubricant rich in albumin and hyaluronic acid that fills the joint cavity, nourishes articular cartilage, and minimizes friction.

Joint (Articular) Capsule

A connective tissue envelope enclosing the joint cavity, composed of an outer fibrous capsule continuous with the periosteum and an inner synovial membrane.

Articular Disc

A fibrocartilage pad that crosses the entire joint capsule between articulating bones, found in the jaw and sternoclavicular joints.

Meniscus

A crescent-shaped fibrocartilaginous pad in the knee that does not cross the joint entirely; absorbs shock, stabilizes the joint, and guides bone movement.

Tendon

A strip or sheet of tough collagenous connective tissue that attaches a muscle to a bone.

Ligament

A strip or sheet of tough collagenous tissue that connects one bone to another bone.

Bursa

A fibrous sac filled with synovial fluid located between adjacent muscles, where tendons pass over bone, or between bone and skin to reduce friction.

Tendon (Synovial) Sheath

An elongated cylindrical bursa wrapped around a tendon, particularly abundant in the hands and feet.

Mechanical Advantage (MA)

The ratio of a lever's output force to its input force, calculated as $MA = \frac{L_E}{L_R}$, where $L_E$ is the effort arm and $L_R$ is the resistance arm.

First-Class Lever

A lever system in which the fulcrum ($F$) is in the middle between the effort ($E$) and the resistance ($R$), as in the atlanto-occipital joint of the neck.

Second-Class Lever

A lever system where resistance ($R$) lies between the fulcrum ($F$) and the effort ($E$), such as bouncing a child on the knee or opening the mouth.

Third-Class Lever

A lever system where the effort ($E$) is applied between the fulcrum ($F$) and resistance ($R$); the most common lever class in the human body, such as forearm flexion.

Range of Motion (ROM)

The degrees through which a joint can move, determined by articular surface structure, ligament tautness, and muscle tone.

Ball-and-Socket Joint

A multiaxial joint where a hemispherical head fits into a cup-like socket, exemplified exclusively by the shoulder and hip joints.

Condylar (Ellipsoid) Joint

A biaxial joint featuring an oval convex surface fitting into a complementary depression, found in radiocarpal and metacarpophalangeal joints.

Saddle Joint

A biaxial joint in which both articulating bones exhibit saddle-shaped surfaces that are concave in one direction and convex in the other, such as the trapeziometacarpal joint.

Plane (Gliding) Joint

A joint with flat articular surfaces where bones slide over each other, usually biaxial, such as intercarpal and intertarsal joints.

Hinge Joint

A monoaxial joint where a convex surface fits snugly into a concave depression, allowing movement in only one plane, such as the elbow and knee.

Pivot Joint

A monoaxial joint in which a bone spins on its longitudinal axis, such as the atlantoaxial joint ($C_1$ and $C_2$) and proximal radioulnar joint.

Flexion

A joint movement that decreases the angle between articulating bones.

Extension

A joint movement that straightens a joint and returns a body part back to the zero position.

Hyperextension

Extension of a joint beyond the zero position / anatomical position.

Abduction

Movement of an extremity or body part in the frontal plane away from the midline of the body.

Adduction

Movement of a body part in the frontal plane toward the median plane / midline.

Circumduction

A sequence of movements combining flexion, abduction, extension, and adduction where the distal end of a limb describes a cone.

Elevation

A movement that raises a body part vertically in the frontal plane, such as shrugging the shoulders.

Depression

A movement that lowers a body part vertically in the frontal plane, such as opening the mouth.

Protraction

The anterior movement of a body part in the transverse (horizontal) plane.

Retraction

The posterior movement of a body part in the transverse (horizontal) plane.

Medial (Internal) Rotation

Movement in which a bone turns on its longitudinal axis toward the midline of the body.

Lateral (External) Rotation

Movement in which a bone turns on its longitudinal axis away from the midline of the body.

Supination

Forearm movement that rotates the radius and ulna parallel to each other, turning the palm to face anteriorly or upward.

Pronation

Forearm movement that crosses the radius over the ulna, turning the palm to face posteriorly or downward.

Opposition

Movement of the thumb across the palm to touch the fingertip of any of the other four fingers.

Dorsiflexion

Movement of the ankle joint that elevates the toes upward, as in taking a forward step.

Plantar Flexion

Movement of the ankle joint extending the foot so that toes point downward, as when standing on tiptoe.

Inversion

Foot movement that tips the soles of the feet medially toward each other.

Eversion

Foot movement that tips the soles of the feet laterally away from each other.

Temporomandibular Joint (TMJ)

Articulation of the mandibular condyle with the mandibular fossa of the temporal bone, supported by lateral and sphenomandibular ligaments and divided by an articular disc.

Glenoid Labrum

A ring of fibrocartilage around the rim of the glenoid cavity that slightly deepens the shallow socket of the shoulder joint.

Rotator Cuff

A tendon sheath formed by the tendons of four muscles (supraspinatus, infraspinatus, teres minor, and subscapularis) that fuse with the shoulder joint capsule.

Humeroulnar Joint

The hinge articulation of the elbow where the trochlea of the humerus joins the trochlear notch of the ulna.

Anular Ligament

A collar-like ligament that encircles the head of the radius and holds it in the radial notch of the ulna at the proximal radioulnar joint.

Acetabular Labrum

A fibrocartilage rim attached to the margin of the acetabulum that deepens the hip socket.

Round Ligament (Ligamentum Teres)

A ligament extending from the fovea capitis of the femoral head to the acetabulum, containing an artery supplying the head of the femur rather than providing joint stability.

Tibiofemoral Joint

The hinge joint formed between the condyles of the femur and the condyles of the tibia; the largest and most complex diarthrosis in the body.

Anterior Cruciate Ligament (ACL)

An intracapsular knee ligament attaching to the anterior tibia that prevents hyperextension of the knee.

Posterior Cruciate Ligament (PCL)

An intracapsular knee ligament that prevents the tibia from sliding backward (posterior displacement) relative to the femur.

Unhappy Triad

A severe knee injury resulting from lateral blows, involving simultaneous damage to the tibial collateral ligament, medial meniscus, and anterior cruciate ligament.

Talocrural Joint

The ankle joint consisting of two articulations (tibia to talus medially, fibula to talus laterally) enclosed within a single joint capsule.

Calcaneal (Achilles) Tendon

A thick tendon extending from the calf muscles to the calcaneus that produces plantar flexion and limits dorsiflexion.

Sprain

An injury in which the reinforcing ligaments of a joint are stretched or torn, commonly occurring at the ankle, knee, and lumbar spine.

Luxation

A dislocation in which articulating bones are forced completely out of normal anatomical alignment.

Subluxation

A partial or incomplete dislocation of a joint.

Osteoarthritis (OA)

A chronic, wear-and-tear degenerative disease where articular cartilage softens and breaks down faster than it can be replaced, often producing bone spurs.

Rheumatoid Arthritis (RA)

A chronic autoimmune inflammatory joint disease where antibodies attack the synovial membrane, causing enzymatic degradation of cartilage and eventual joint ossification (ankylosis).

Gouty Arthritis

A metabolic form of arthritis caused by the deposition of uric acid crystals into joints and soft tissues, most commonly affecting the base of the great toe.

Arthroplasty

The surgical replacement of a damaged joint with an artificial joint prosthesis.

Arthroscopy

A minimally invasive surgical procedure in which the interior of a joint cavity is examined and treated using a slender, pencil-thin arthroscope through a small incision.