8

Joints Come in Many Types

Joints (Articulations)

• Functions of joints

• Classifying Joints: Functional orStructural

• Naming Movements of Bones AroundJoints

• Types of Joints Based on Movement

• Selected Key Joints: Shoulder, Elbow,Hip, Knee

• Joint Injuries

• Chronic Joint Conditions: Arthritis

Joints (Articulations)

•Definition: site where two or more bones meet

•Functions of joints:

•Give skeleton mobility

•Hold skeleton together

•Joint classification

•Structural classification (material binding bones together andwhether or not a joint cavity is present)

•Fibrous joints (sutures, syndesmoses, gomphoses)

•Cartilaginous

•Synovial

• Functional classification (amount of movement allowed by the joint)

•Synarthroses—immovable

•Amphiarthroses—slightly movable

•Diarthroses—freely movable

Fibrous Joints

•Bones joined by dense fibrous connectivetissue

•No joint cavity

•Most are synarthrotic (immovable)

•Three types:

•Sutures

•Syndesmoses

•Gomphoses

Dense

fibrous

connective

tissue

Suture

line

(a) Suture

Joint held together with very short,

interconnecting fibers, and bone edges

interlock. Found only in the skull.

• Rigid, interlockingjoints containingshort connectivetissue fibers

• Allow for growthduring youth

• In middle age,sutures ossify andare calledsynostoses

Fibula

Tibia

Ligament

(b) Syndesmosis

Joint held together by a ligament.

Fibrous tissue can vary in length, but

is longer than in sutures.

•Bones connected byligaments (bands offibrous tissue)

•Movement variesfrom immovable toslightly movable

•Examples:

•Synarthrotic distaltibiofibular joint

•Diarthroticinterosseousconnectionbetween radiusand ulna

Root of

tooth

Socket of

alveolar

process

Periodontal

ligament

“Peg in socket” fibrous joint. Periodontal

ligament holds tooth in socket.

•Peg-in-socketjoints of teeth inalveolar sockets

•Fibrousconnection is theperiodontalligament

Joints (Articulations)

•Definition: site where two or more bones meet

•Functions of joints:

•Give skeleton mobility

•Hold skeleton together

•Joint classification

•Structural classification (material binding bones together andwhether or not a joint cavity is present)

•Fibrous joints (sutures, syndesmoses, gomphoses)

•Cartilaginous

•Synovial

• Functional classification (amount of movement allowed by the joint

•Synarthroses—immovable

•Amphiarthroses—slightly movable

•Diarthroses—freely movable

Cartilaginous Joints

•Bones united by cartilage

•No joint cavity

•Two types:

•Synchondroses

•Symphyses

Types of Cartilaginous Joints

(all are synarthrotic- don’t move)

(are strong, flexible amphiarthroses)

Hyaline cartilage that covers articular surfaces

Joints (Articulations)

•Definition: site where two or more bones meet

•Functions of joints:

•Give skeleton mobility

•Hold skeleton together

•Joint classification

•Structural classification (material binding bones together andwhether or not a joint cavity is present)

•Fibrous joints (sutures, syndesmoses, gomphoses)

•Cartilaginous

•Synovial

• Functional classification (amount of movement allowed by the joint

•Synarthroses—immovable

•Amphiarthroses—slightly movable

•Diarthroses—freely movable

Synovial Joints (Diarthrotic (freely movable)- most of body’s joints)

Distinguishing features:

1.Articular cartilage: hyaline cartilage

2.Joint (synovial) cavity: small potential space

3.Articular (joint) capsule

•Outer fibrous capsule of dense irregularconnective tissue

•Inner synovial membrane of loose connectivetissue (type of integument)

4.Synovial fluid

•Viscous slippery filtrate of plasma + hyaluronicacid

•Lubricates and nourishes articular cartilage

5.Three possible types of reinforcingligaments

•Capsular (intrinsic)—part of the fibrous capsule

•Extracapsular—outside the capsule

•Intracapsular—deep to capsule; covered bysynovial membrane

6.Rich nerve and blood vessel supply

•Nerve fibers detect pain, monitor joint positionand stretch

•Capillary beds produce filtrate for synovial fluid

Bone A

Bone B

Synovial Joints: Friction-Reducing Structures

•Bursae

•Flattened, fibrous sacs lined withsynovial membranes

•Contain synovial fluid

•Commonly act as “ball bearings”where ligaments, muscles, skin,tendons, or bones rub together

•Inflammation from overuse orstress of joint causes bursitis

•Tendon sheath

•Elongated bursa that wrapscompletely around a tendon

•Inflammation from stress oroveruse causes tendonitis

Synovial Joints: Stabilization, Movement, Range of Motion

•Stabilizing Factors

•Shapes of articular surfaces (minor role)

•Ligament number and location (limited role)

•Muscle tone, which keeps tendons that cross the joint taut

•Extremely important in reinforcing shoulder and knee joints and arches of thefoot

•Movement

•Muscle attachments across a joint (will learn details when we learn muscles)

•Origin—attachment to the immovable bone

•Insertion—attachment to the movable bone

•Muscle contraction causes the insertion to move toward the origin

•Movements occur along transverse, frontal, or sagittal planes

•Range of Motion (don’t need to know)

•Nonaxial—slipping movements only

•Uniaxial—movement in one plane

•Biaxial—movement in two planes

•Multiaxial—movement in or around all three planes

Joints (Articulations)

• Functions of joints

• Classifying Joints: Functional orStructural

• Naming Movements of Bones AroundJoints

• Types of Joints Based on Movement

• Selected Key Joints: Shoulder, Elbow,Hip, Knee

• Joint Injuries

• Chronic Joint Conditions: Arthritis

Movements at Synovial Joints

1.Gliding

2.Angular movements

•Flexion, extension, hyperextension

•Abduction, adduction

•Circumduction

3.Rotation

•Medial and lateral rotation

4.Angular movements:

•Flexion, extension, hyperextension

•Abduction, adduction

5. Other movements

•Dorsiflexion, plantar flexion

•Inversion, eversion

•Protraction, retraction

•Elevation, depression

•Opposition

Figure 8.5a

Gliding

(a) Gliding movements at the wrist

Figure 8.5b

(b) Angular movements: flexion, extension, and

hyperextension of the neck

Hyperextension

Extension

Flexion

Figure 8.5c

Hyperextension

Flexion

Extension

Figure 8.5d

Extension

Flexion

(d) Angular movements: flexion and extension at theshoulder and knee

Figure 8.5e

Abduction

Adduction

(e) Angular movements: abduction, adduction, andcircumduction of the upper limb at the shoulder

Circumduction

Figure 8.5f

Lateral

rotation

Medial

rotation

Rotation

(f) Rotation of the head, neck, and lower limb

Figure 8.6a

Supination

(radius and

ulna are

parallel)

(a) Pronation (P) and supination (S)

Pronation

(radius

rotates

over ulna)

Figure 8.6b

Dorsiflexion

Plantar flexion

Dorsiflexion

Plantar flexion

(b) Dorsiflexion and plantar flexion

Figure 8.6c

Eversion

Inversion

Figure 8.6d

Protraction

of mandible

Retraction

of mandible

(d) Protraction and retraction

Figure 8.6e

Elevation

of mandible

Depression

of mandible

(e) Elevation and depression

Figure 8.6f

(f) Opposition

Opposition