Chapter 9
Joints

Joints hold bones together but permit movement

Point of contact

between 2 bones

between cartilage and bone

between teeth and bones

Arthrology = study of joints

Kinesiology = study of motion

Classification of Joints

Structural classification based upon:

presence of space between bones

type of connective tissue holding bones together

collagen fibers

cartilage

joint capsule & accessory ligaments

Functional classification based upon movement:

immovable = synarthrosis

slightly movable = amphiarthrosis

freely movable = diarthrosis

Fibrous Joints

Lack a synovial cavity

Bones held closely together by fibrous connective tissue

Little or no movement (synarthroses or amphiarthroses)

structural type

sutures

syndesmoses

gomphoses

Sutures

Thin layer of dense fibrous connective tissue unites bones of the skull

Immovable (synarthrosis)

If fuse completely in adults is synostosis

Syndesmosis

Fibrous joint

bones united by ligament

Slightly movable (amphiarthrosis)

Anterior tibiofibular joint and Interosseous membrane

Gomphosis

Ligament holds cone-shaped peg in bony socket

Immovable (amphiarthrosis)

Teeth in alveolar processes

Cartilaginous Joints

Lacks a synovial cavity

Allows little or no movement

Bones tightly connected by fibrocartilage or hyaline cartilage

2 types

synchondroses

symphyses

Synchondrosis

Connecting material is hyaline cartilage

Immovable (synarthrosis)

Epiphyseal plate or joints between ribs and sternum

Symphysis

Fibrocartilage is connecting material

Slightly movable (amphiarthroses)

Intervertebral discs and pubic symphysis

Synovial Joints

Synovial cavity separates articulating bones

Freely moveable (diarthroses)

Articular cartilage

reduces friction

absorbs shock

Articular capsule

surrounds joint

thickenings in fibrous
capsule called ligaments

Synovial membrane

inner lining of capsule

secretes synovial fluid containing hyaluronic acid slippery)

brings nutrients to articular cartilage

Example of Synovial Joint

Joint space is synovial joint cavity

Articular cartilage covering ends of bones

Articular capsule

Other Special Features

Accessory ligaments

extracapsular ligaments

outside joint capsule

intracapsular ligaments

within capsule

Articular discs or menisci

attached around edges to capsule

allow 2 bones of different shape to fit tightly

increase stability of knee - torn cartilage

Bursae = saclike structures between structures

skin/bone or tendon/bone or ligament/bone

Arthroscopy & Arthroplasty

Arthroscopy = examination of joint

instrument size of pencil

remove torn knee cartilages & repair ligaments

small incision only

Arthroplasty = replacement of joints

total hip replaces acetabulum & head of femur

plastic socket & metal head

knee replacement common

Torn Cartilage and Arthroscopy

Damage to menisci of the knee joint

Visualization of the inside of a joint

arthroscope

requires only small incisions

Repair may include removal of torn cartilage

Nerve and Blood Supply

Nerves to joints are branches of nerves to nearby muscles

Joint capsule and ligaments contain pain fibers and sensory receptors

Blood supply to the structures of a joint are branches from nearby structures

supply nutrients to all joint tissues except the articular cartilage which is supplied from the synovial fluid

Sprain versus Strain

Sprain

twisting of joint that stretches or tears ligaments

no dislocation of the bones

may damage nearby blood vessels, muscles or tendons

swelling & hemorrhage from blood vessels

ankle if frequently sprained

Strain

less serious injury

overstretched or partially torn muscle

Planar Joint

Bone surfaces are flat or slightly curved

Side to side movement only

Rotation prevented by ligaments

Examples

intercarpal or intertarsal joints

sternoclavicular joint

vertebrocostal joints

Hinge Joint

Convex surface of one bones fits into concave surface of 2nd bone

Uniaxial like a door hinge

Examples

Knee, elbow, ankle, interphalangeal joints

Movements produced

flexion = decreasing the joint angle

extension = increasing the angle

hyperextension = opening the joint beyond the anatomical position

Flexion, Extension & Hyperextension

Pivot Joint

Rounded surface of bone articulates with ring formed by 2nd bone & ligament

Monoaxial since it allows only rotation around longitudinal axis

Examples

Proximal radioulnar joint

supination

pronation

Atlanto-axial joint

turning head side to side “no”

Condyloid or Ellipsoidal Joint

Oval-shaped projection fits into oval depression

Biaxial = flex/extend or abduct/adduct is possible

Examples

wrist and metacarpophalangeal joints for digits 2 to 5

Abduction and Adduction

Saddle Joint

One bone saddled-shaped; other bone fits as a person would sitting in that saddle

Biaxial

Circumduction allows tip of thumb travel in circle

Opposition allows tip of thumb to touch tip of other fingers

Example

trapezium of carpus and metacarpal of the thumb

Ball and Socket Joint

Ball fitting into a cuplike depression

Multiaxial

flexion/extension

abduction/adduction

rotation

Examples

shoulder joint

hip joint

Bursae and Tendon Sheaths

Bursae

fluid-filled saclike extensions of the joint capsule

reduce friction between moving structures

skin rubs over bone

tendon rubs over bone

Tendon sheaths

tubelike bursae that wrap around tendons at wrist and ankle where many tendons come together in a confined space

Bursitis

chronic inflammation of a bursa

Summary of Movements at Synovial Joints

Gliding

no change in angle of joint

Angular movements

increase or decrease in angle between articulating bones

flexion, extension, hyperextension

adduction, abduction

circumduction is a combination of above movements

Rotation

bone revolves around its own axis

Special movements

uniquely named movements for jaw, hand and foot

Circumduction

Movement of a distal end of a body part in a circle

Combination of flexion, extension, adduction and abduction

Occurs at ball and socket, saddle and condyloid joints

Rotation

Bone revolves around its own longitudinal axis

medial rotation is turning of anterior surface in towards the midline

lateral rotation is turning of anterior surface away from the midline

At ball & socket and pivot type joints

Special Movements of Mandible

Elevation = upward

Depression = downward

Protraction = forward

Retraction = backward

Special Hand & Foot Movements

Inversion

Eversion

Dorsiflexion

Plantarflexion

Pronation

Supination

Shoulder Joint

Head of humerus and glenoid cavity of scapula

Ball and socket

All types of movement

Glenohumeral (Shoulder) Joint

Articular capsule from glenoid cavity to anatomical neck

Glenoid labrum deepens socket

Many nearby bursa (subacromial)

Supporting Structures at Shoulder

Associated ligaments strengthen joint capsule

Transverse humeral ligament holds biceps tendon in place

Rotator Cuff Muscles

Attach humerus to scapula

Encircle the joint supporting the capsule

Hold head of humerus in socket

Elbow Joint

Hinge joint

trochlea notch of ulna and trochlea of humerus

flexion and extension of elbow

Pivot joint

head of radius and capitulum of humerus

supination and pronation of forearm

Articular Capsule of the Elbow Joint

Radial annular ligament hold head of radius in place

Collateral ligaments maintain integrity of joint

Hip Joint

Head of femur and acetabulum of hip bone

Ball and socket type of joint

All types of movement possible

Hip Joint Structures

Acetabular labrum

Ligament of the head of the femur

Articular capsule

Hip Joint Capsule

Dense, strong capsule reinforced by ligaments

iliofemoral ligament

ischiofemoral ligament

pubofemoral ligament

One of strongest structures in the body

Tibiofemoral Joint

Between femur, tibia and patella

Hinge joint between tibia and femur

Gliding joint between patella and femur

Flexion, extension, and slight rotation of tibia on femur when knee is flexed

Tibiofemoral Joint

Articular capsule

mostly ligs & tendons

Lateral & medial menisci = articular discs

Many bursa

Vulnerable joint

Knee injuries damage ligaments & tendons since bones do not fit together well

External Views of Knee Joint

Patella is part of joint capsule anteriorly

Rest of articular capsule is extracapsular ligaments

Fibular and tibial collateral ligaments

Intracapsular Structures of Knee

Medial meniscus

C-shaped fibrocartilage

Lateral meniscus

nearly circular

Posterior cruciate ligament

Anterior cruciate ligament

Temporomandibular Joint

Synovial joint

Articular disc

Gliding above disc

Hinge below disc

Movements

depression

elevation

protraction

retraction

Atlanto-occipital joints

Atlas and occipital condyles

Condyloid Joint

Flexion

Extension

Slight lateral tilting

Intervertebral Joints

Between bodies and intervertebral discs

symphysis

Between vertebral articular processes

synovial

Flexion

Extension

Lateral flexion

Elbow Joint

Trochlea of humerus, trochlear notch of ulna & head of radius

Pivot and hinge types

Flexion, extension, pronation & supination

Radiocarpal Joint

Articular disc

Condyloid type

Flexion, extension, abduction & adduction

Talocrural Joint

Tibia & fibula with talus

Hinge

Inversion, eversion, plantarflexion & dorsiflexion

Range of Motion in a Synovial Joint

Shape of articulating bones

Tension & strength of joint ligaments

Arrangement of muscles around joints

Apposition (coming together) of soft parts

Hormones

relaxin from placenta loosens pubic symphysis

Disuse

decreased synovial fluid, decreased flexibility of ligaments, reduced size of muscles

Rheumatoid Arthritis

Autoimmune disorder

Cartilage attacked

Inflammation, swelling & pain

Final step is fusion of joint

Osteoarthritis

Degenerative joint disease

aging, wear & tear

Noninflammatory---no swelling

only cartilage is affected not synovial membrane

Deterioration of cartilage produces bone spurs

restrict movement

Pain upon awakening--disappears with movement

Gouty Arthritis

Urate crystals build up in joints---pain

waste product of DNA & RNA metabolism

builds up in blood

deposited in cartilage causing inflammation & swelling

Bones fuse

Middle-aged men with abnormal gene