CHAPTER 8: JOINTS

Site where two or more bones meet

Articulation

What are the functions of joints?

Give skeleton mobility, hold skeleton together

What are FUNCTIONAL classifications of joints?

Synarthroses, amphiarthroses, diarthroses

Immovable joints

Synarthroses

Slightly moveable joints

Amphiarthroses

Freely moveable joints

Diarthroses

What are the STRUCTURAL classifications of joints?

Fibrous, cartilaginous, synovial

Bones joined by dense fibrous connective tissue

No joint cavity

Most synarthrotic (immovable)

Depends on length of connective tissue fibers

Fibrous joints

What are the three types of fibrous joints?

Sutures, syndesmoses, gomphoses

Found in skull

Rigid, interlocking joints

Immovable joints for protection of brain

Contain short connective tissue fibers

Allow for growth during youth

In middle age, ossify and fuse (called synostoses)

Sutures

Bones connected by ligaments (bands of fibrous tissue)

Fiber length varies so movement varies, I.e,

• little to no movement at distal tibiofibular joint

• Large amount of movement at interosseous membrane connecting radius and ulna

Syndesmoses

Peg in socket joints of teeth in alveolar sockets

Fibrous connection is the periodontal ligament

Gomphoses

Bones united by cartilage

No joint cavity

Not highly moveable

Cartilaginous joints

What are the two types of cartilaginous joints?

Synchondroses, symphyses

Bar/plate of hyaline cartilage unites bones e.g.,

• temporary epiphyseal plate joints (become synostoses after plate closure)

Cartilage of 1st rib with manubrium

All are synarthrotic

Synchondroses

Fibrocartilage unites bone (hyaline cartilage present as articular cartilage)

Strong, flexible amphiarthroses

Symphyses

Bones separated by fluid filled joint cavity

All are diarthrotic

Include: all limb joints, most joints of body

Synovial joints

Prevents crushing of bone ends

Articular cartilage

Small, fluid filled potential space

Joint (synovial) cavity

Two layers:

External fibrous layer (dense irregular connective tissue)

Inner synovial membrane (loose connective tissue, makes synovial fluid)

Articular (joint) capsule

Viscous. slippery filtrate of plasma and hyaluronic acid

Lubricates and nourished articular cartilage

Contains phagocytic cells to remove microbes and debris

Synovial Fluid

What are the three different types of reinforcing ligaments?

Capsular, extracapsular, intracapsular

Thickened part of fibrous layer

Capsular

Outside the capsule

Extracapsular

Deep to capsule; covered by synovial membrane

Intracapsular

For cushioning between fibrous layer and synovial membrane or bone

fatty pads

Fibrocartilage separates articular surfaces to improve “fit” of bone ends, stabilize joint, and reduce wear and tear

Articular discs

Sacs lined with synovial membrane (contain synovial fluid)

Reduce friction where ligaments, muscles, skin, tendons, or bones rub together

Bursae

Elongated bursa wrapped completely around tendon subjected to friction

Tendon sheaths

Attachment to immovable bone

Origin

Attachment to moveable bone

insertion

Slipping movements only

Nonaxial

Movement in one plane

Uniaxial

Movement in two planes

Biaxial

Movement in or around all three planes

Multiaxial

What are the three general types of movement at synovial joints?

gliding, angular movements, rotation

One flat bone surface glide or slips over another similar surface

Ex: intercarpal joints, intertarsal joints, between articular processes of vertebrae

Gliding movments

Increase or decrease angle between two bones

Movement along sagittal/frontal plane

Angular movements

Decreases the angle of the joint

Flexion

Increases the angle of the joint

Extension

Excessive extension and beyond normal range of motion

Hyperextension

Movement away from the midline

Abduction

Movement toward the midline

Adduction

Involves flexion, abduction, extension, and adduction of limb

Limb describes cone in space

Circumduction

Turning of bone around its own long axis

Toward midline or away from it

Medial and lateral rotation

Ex: between C1 and C2 vertebrae, rotation of humerus and femur

Rotation

Largest most complex joint of body

Three joints surrounded by a single joint cavity

Knee Joint

Plane joint

Allows gliding motion during knee flexion

Femoropatellar joint

Femoral condyles with lateral and medial menisci of tibia

Allows flexion, extension, and some rotation when knee partly flexed

Lateral and medial tibiofemoral joints

Ball and socket joint (head of humerus w/ glenoid cavity of scapula)

Most freely moving joint in body (stability sacrificed)

Shoulder (glenohumeral) joint

Ball and socket joint (head of femur articulates with acetabulum)

Good range of motion, but limited by the deep socket

Hip (coxal) joint

Rim of fibrocartilage the enhances depth of socket, making hip dislocations rare

Acetabular Labrum

Mandibular condyle articulates with temporal bone

Most easily dislocated joint in the body

Temporomandibular Joint (TMJ)