Anatomy of Joints: Types, Structures, and Movements in Skeletal System

Joints (Articulations)

Functional connections between bones that bind parts of the skeletal system together, make bone growth possible, permit parts of the skeleton to change shape during childbirth, and enable body to move in response to skeletal muscle contractions.

Fibrous Joints

Joints held together by dense connective tissue containing many collagen fibers, found in bones in close contact.

Cartilaginous Joints

Joints connected by hyaline cartilage or fibrocartilage.

Synovial Joints

Joints that have a complex structure.

Synarthrotic Joints

Immovable joints.

Amphiarthrotic Joints

Slightly movable joints.

Diarthrotic Joints

Freely movable joints.

Syndesmosis

Fibrous joint where bones are bound by a sheet of dense connective tissue (interosseous membrane) or a bundle of dense connective tissue (interosseous ligament); amphiarthrotic (flexible, may twist).

Suture

Fibrous joint where a thin layer of connective tissue (sutural ligament) connects bones; synarthrotic (immovable) between flat bones of the skull.

Gomphosis

Fibrous joint characterized by a cone-shaped bony process in a socket; synarthrotic (immovable), such as the root of a tooth in maxilla or mandible held in place by periodontal ligament.

Synchondrosis

Cartilaginous joint where bands of hyaline cartilage unite bones; synarthrotic, with some being temporary (e.g., epiphyseal plate) and others permanent (e.g., between manubrium and the first rib).

Symphysis

Cartilaginous joint with a pad of fibrocartilage between bones, articular surfaces covered by hyaline cartilage; amphiarthrotic (limited movement), such as pubic symphysis and joint between bodies of adjacent vertebrae (intervertebral discs).

Costochondritis

Inflammation of the costal cartilages, which connect the ribs to the sternum.

Costosternal joint

Involves the synchondrosis between the manubrium of the sternum and the first rib.

Costochondral joints

Involves the synovial joints between the costal cartilages of ribs 2-7 and the body of the sternum.

Symptoms of Costochondritis

Causes chest pain during deep breaths or certain types of movements, along with tenderness in the area where the ribs meet the sternum.

Causes of Costochondritis

Can be caused by overexertion during exercise such as weightlifting or from forceful coughing.

Structure of a synovial joint

Articular cartilage covers articular ends of bones.

Joint capsule

Consists of 2 layers: outer fibrous layer, composed of ligaments, and inner layer, synovial membrane, which secretes synovial fluid.

Parts of Synovial Joints

Include articular cartilage, joint capsule, ligaments, synovial membrane, synovial cavity, synovial fluid, meniscus (-i) in some joints, and bursa (-ae) in some joints.

Ball-and-Socket Joint

Also called spheroidal joint; has a round head in a cup-shaped cavity, allowing the widest range of motion.

Condylar Joint

Also called ellipsoidal joint; has an oval condyle that fits into an elliptical cavity, allowing back-and-forth and side-to-side movement.

Plane Joint

Also called gliding joint; has almost flat or slightly curved surfaces, allowing back-and-forth and twisting movements.

Hinge Joint

Convex surface fits into concave surface of another bone, allowing uniaxial movement (in 1 plane).

Pivot Joint

Also called trochoid joint; has a cylindrical surface that rotates within a ring of another bone, allowing uniaxial movement (rotation only).

Saddle Joint

Also called sellar joint; both bones have concave and convex surfaces, allowing biaxial movement (in 2 planes).

Origin

Relatively fixed end of a skeletal muscle

Insertion

More movable end of a skeletal muscle

Flexion

Bending of parts at a joint

Extension

Straightening of parts at a joint

Hyperextension

Extension beyond normal anatomical position

Lateral flexion

Bending to the side

Abduction

Moving a part of body away from midline

Adduction

Moving a part of body toward midline

Dorsiflexion

Ankle movement which points toes upward

Plantar flexion

Ankle movement which points toes downward

Circumduction

Movement of a part of body in circular path

Rotation

Moving a part of body around an axis

Medial rotation

Movement of limb so anterior surface moves toward midline

Lateral rotation

Movement of limb so anterior surface moves away from midline

Supination

Forearm rotation so palm faces upward or forward, or lying down face up (supine)

Pronation

Forearm rotation so palm faces downward or backward, or lying down face down (prone)

Inversion

Turning of foot so plantar surface faces midline

Eversion

Turning of foot so plantar surface faces away from midline

Protraction

Movement of a body part forward

Retraction

Movement of a body part backward

Elevation

Raising a body part

Depression

Lowering a body part

Jaw Joint

Also called the Temporomandibular Joint, TMJ; modified hinge joint between the mandibular condyle of the mandible and the mandibular fossa of the temporal bone

Articular disc

Consisting of fibrocartilage, separates the synovial cavity into 2 portions

Main ligaments of Jaw Joint

Sphenomandibular ligament and Lateral (temporomandibular) ligament

Temporomandibular Joint Syndrome

An articulation problem between the mandibular condyle of the mandible and the mandibular fossa of the temporal bone.

Causes of TMJ Syndrome

Misaligned jaw, grinding or clenching of teeth, sitting or standing in one place for many hours.

Symptoms of TMJ Syndrome

Pain in the face, head, back, or in front of ears, ringing in the ears, clicking/popping of the jaw, insomnia, temperature sensitivity in the teeth, dizziness.

Diagnosis of TMJ Syndrome

Diagnosed via an electromyograph, which records activity in 4 pairs of head and neck muscles.

Treatments for TMJ Syndrome

Eating soft foods, using ice packs, performing relaxation techniques, massage, physical therapy stretching exercises, antidepressants, injections of botulinum toxin or corticosteroids, arthrocentesis, oral appliances, surgery to repair joint or replace it.

Shoulder Joint

Ball-and-socket joint formed by the head of humerus and glenoid cavity of scapula.

Loose Joint Capsule

A characteristic of the shoulder joint that allows for a wide range of movement.

Glenoid Labrum

A fibrocartilaginous structure that deepens the glenoid cavity of the scapula.

Major Ligaments of the Shoulder Joint

Coracohumeral ligament, glenohumeral ligaments, transverse humeral ligament.

Elbow Joint

Contains 2 articulations: a hinge joint and a plane (gliding) joint.

Hinge Joint of Elbow

Between trochlea of humerus and trochlear notch of ulna, allowing flexion/extension only.

Plane Joint of Elbow

Between capitulum of humerus and fovea on head of radius, allowing pronation/supination.

Major Ligaments of Elbow Joint

Radial collateral ligament, ulnar collateral ligament, anular ligament.

Hip Joint

Ball-and-socket joint consisting of head of femur and acetabulum of hip bone.

Acetabular Labrum

A fibrocartilaginous rim that surrounds the acetabulum of the hip joint.

Major Ligaments of the Hip Joint

Iliofemoral ligament (strongest ligament in body), pubofemoral ligament, ischiofemoral ligament.

Knee Joint

Largest and most complex synovial joint consisting of femur, tibia, and patella.

Bones of the Knee Joint

Femur: medial and lateral condyles of distal end; Tibia: medial and lateral condyles of proximal end; Patella: articulates with anterior surface of femur.

Movements of the Knee Joint

Flexion/extension, and some rotation when knee is flexed.

Menisci in Knee Joint

Crescent-shaped cartilages that separate femur and tibia.

Patellar ligament

A major ligament of the knee joint.

Oblique popliteal ligament

A major ligament of the knee joint.

Arcuate popliteal ligament

A major ligament of the knee joint.

Tibial (medial) collateral ligament

A major ligament of the knee joint.

Fibular (lateral) collateral ligament

A major ligament of the knee joint.

Anterior cruciate ligament

A major ligament of the knee joint.

Posterior cruciate ligament

A major ligament of the knee joint.

Joint injuries

Result from trauma, overuse, infection, inappropriate immune attack, degeneration.

Arthroscopy

Used to treat shoulder, elbow, knee injuries, and can be used to diagnose certain conditions.

Dislocations

Displacement of articulating surfaces; common in shoulder, knee, fingers, jaw.

Sprain

Tearing of connective tissue in joint, without bone dislocation.

Torn Ligament

Result from twist, overextension, lifting heavy object, or fall.

Bursitis

Inflammation of a bursa, from overuse or stress.

Arthritis

Inflammation, swelling, and pain in a joint.

Rheumatoid arthritis

An autoimmune disease.

Osteoarthritis

Degenerative, most common type, occurs with aging.

Lyme arthritis

Caused by Lyme disease, passed through tick bite.

Gout

A type of inflammatory arthritis, caused by uric acid crystalizing in joints such as big toe.

Synthetic materials in joint replacement

Used to replace joints damaged by arthritis or injury.

Common materials for joint replacement

Steel and titanium replace larger joints, silicone used for smaller joints, some are ceramic.

Hip replacements

The most common type of joint replacement.

New technology for joint replacement

Includes use of materials resembling natural body chemicals and 3D printing technology for custom joints.

Joint stiffness

An early sign of aging.

Aging and arthritis

Many people develop arthritis as they age.

Changes in fibrous joints

Fibrous joints are the first to change; can strengthen, however, over a lifetime.

Cartilage in synchondroses

Stiffens with age.

Ligaments and elasticity

Ligaments lose elasticity with age.

Changes in symphysis joints

Diminish flexibility and decrease height due to water loss from intervertebral discs.

Disuse effects on joints

Disuse hampers the nutrient supply to joints; speeds up stiffening.