Chapter 9 Articulations

place where a bone meets another bone, cartilage, or teeth

•Study of joints = arthrology

Classification by structure:

•Fibrous joint: bones held together by dense regular connective tissue

•Cartilaginous joint: bones joined by cartilage

•Synovial joint: bones separated by fluid-filled cavity

Classification by function:

•Synarthrosis: immobile joint

•Amphiarthrosis: slightly mobile joint

•Diarthrosis: freely moveable joint

Bones joined by dense regular CT

•Gomphoses: joints- teeth and maxilla and mandible; synarthroses

•Sutures: joints between skull bones; synarthroses

•Syndesmoses: joints between parallel bones in the forearm and leg (radius and ulna, tibia and fibula); amphiarthroses

Bones attached by cartilage

•Synchondroses: bones joined by hyaline cartilage; synarthroses

•Ex: epiphyseal plate, costochondral joints

•Symphyses: bones joined by pad of fibrocartilage; amphiarthroses

•Ex: pubic symphysis, intervertebral joints

Freely mobile diarthroses

Articulating bones separated by a joint cavity

The articular capsule contains two layers:

1.Outer fibrous layer made of dense regular CT; strengthens joint

2.Inner synovial membrane that secretes lubricating synovial fluid

Articular cartilage Thin layer of hyaline cartilage that covers articulating surfaces, shock absorber

Joint cavity

•Space between articulating bones

Ligaments connect bone to bone

•Dense regular connective tissue, Strengthen and reinforce capsule

Sensory nerves detect pain and stretch

Blood vessels nourish the joint

Bursae: sacs outside most synovial joints where ligaments, muscles, tendons, or bones rub; contain synovial fluid

Tendon sheaths: elongated bursae around tendons (which connect muscle to bone), particularly in confined areas such as the wrist and ankle where tendons rub each other

Fat pads: packing material; also provide some protection

Classified by shapes of articulating surfaces and amount of movement allowed

1.Uniaxial: joint moves in one plane or axis

2.Biaxial: joint moves in two planes or axes

3.Multiaxial: joint moves in three planes or axes

1.Plane joints: uniaxial; side to side movement

2.Hinge joints: uniaxial; like hinge of a door

3.Pivot joints: uniaxial; one bone rotates on its longitudinal axis

4.Condylar joints: biaxial; oval, concave surface of one bone; convex of the other

5.Saddle joints: biaxial; joint surfaces resemble saddle shape

6.Ball-and-socket joints: multiaxial; spherical head into cuplike socket

back-and-forth or side-to-side

Angle between bones does not change

Occurs mainly in plane joints

•Ex: between carpals

Increases or decreases the angle between bones

•Flexion: movement in anterior-posterior plane where joint angle is decreased

•Extension: movement in anterior-posterior plane where joint angle is increased

•Hyperextension: extension beyond normal range of motion

•Lateral flexion: body trunk moves laterally in coronal plane

•Abduction: lateral movement of body part away from midline

•Adduction: medial movement of body part toward midline

•Circumduction: proximal end of bone stationary while distal end makes a circular (cone) shape

During rotation, a bone turns on its own longitudinal axis

•Atlantoaxial joint turning back-and-forth in the “no” gesture

•Limbs turning to and from median plane

•Lateral rotation: anterior surface of bone turned laterally

•Medial rotation: anterior surface of bone turned medially

•Pronation: medial rotation of forearm; palm turns inferiorly or posteriorly

•Supination: lateral rotation of forearm; palm turns superiorly or anteriorly

TMJ is the articulation between the head of the mandible and the articular tubercle of the temporal bone anteriorly and mandibular fossa posteriorly

Diarthrotic, synovial hinge joint

•Articular disc

•Sphenomandibular, stylomandibular, and temporomandibular ligaments

Amphiarthroses between vertebral bodies;

diarthroses between articular processes

Vertebral bodies separated by intervertebral discs, composed of:

•Outer anulus fibrosus composed of fibrocartilage

•Inner gelatinous nucleus pulposus, composed of water and fibers

Ligaments: anterior and posterior longitudinal, interspinous, supraspinous, ligamentum nuchae, ligamentum flavum

Diarthrotic saddle joint between manubrium of sternum and sternal end of the clavicle

Articular disc separates two joint cavities

Wide range of movement

Supporting ligaments:

•Anterior and posterior sternoclavicular

•Costoclavicular

•Interclavicular

Diarthrotic plane joint between acromial end of clavicle and acromion of scapula

Articular disc within joint cavity

Supporting ligaments:

•Acromioclavicular

•Coracoclavicular

Diarthrotic ball-and-socket joint between head of humerus and glenoid cavity of scapula

Greatest range of movement (but also the most unstable) of any joint in body

Features:

•Fibrocartilaginous glenoid labrum

•Ligaments: coracoacromial, coracohumeral, glenohumeral

•Tendon of biceps brachii long head

•Rotator cuff muscles

•Bursae: subacromial, subcoracoid, subdeltoid, and subscapular

Diarthrotic hinge joint composed of humeroulnar and humeroradial joints

•Trochlea of humerus with trochlear notch of ulna

•Capitulum of humerus with head of radius

•Both joints enclosed in single articular capsule

Supporting ligaments:

•Radial collateral (lateral collateral)

•Ulnar collateral (medial collateral)

•Anular

Diarthrotic condylar joint between the three proximal carpal bones (scaphoid, lunate, triquetrum), the distal articular surface of radius, and an articular disc

•Articular disc separates joint from ulna (so ulna is not part of wrist joint)

Intercarpal articulations increase movement capability of wrist

Diarthrotic ball-and-socket joint between head of femur and acetabulum of os coxae

Features

•Fibrocartilaginous acetabular labrum deepens socket

•Articular capsule with retinacular fibers around neck of femur

•Ligaments:

•Iliofemoral

•Ischiofemoral

•Pubofemoral

•Ligament of head of femur

Diarthrotic hinge joint containing two articulations:

•Tibiofemoral joint between tibial condyles and femoral condyles

•Medial and lateral menisci are fibrocartilage pads on tibial condyles

•Patellofemoral joint between patella and patellar surface of femur

Largest and most complex diarthrosis of body

Supporting structures:

•Quadriceps tendon continuous with patellar ligament

•Fibular (lateral) collateral ligament

•Tibial (medial) collateral ligament

•Anterior and posterior cruciate ligaments (ACL and PCL)

Diarthrotic hinge joint composed of two articulations:

•Between distal end of tibia and the talus

•Between distal end of fibula and the lateral aspect of the talus

Supporting ligaments:

•Deltoid

•Lateral

•Anterior and posterior tibiofibular

Four types of synovial diarthroses in foot:

•Intertarsal: plane joint between tarsals

•Tarsometatarsal: plane joint between distal tarsal bones and metatarsals

•Metatarsophalangeal (MP): condylar joint between metatarsal and proximal phalanges

•Interphalangeal (IP): hinge joint between phalanges

Wear and tear over time affects joint size, shape, and flexibility

May calcify with age or injury

•E.g., bone formation at margins of cartilaginous joints

Moderate exercise nourishes cartilage and helps strengthen joints, keeping them healthy

Arthritis is a common inflammatory or degenerative disease that comes in many forms:

•Gouty arthritis: urate crystals accumulate in synovial joints

•Osteoarthritis (OA): wear-and-tear arthritis

•Rheumatoid arthritis (RA): autoimmune; immune cells target own body cells (joint tissue)

Begin to develop during sixth week and become better differentiated during fetal period

Mesenchyme becomes connective tissue surrounding and within joints

Synovial joint development is more complex compared to fibrous and cartilaginous