Joints

Joints (articulation)

• Defined: A point of contact between bones, between cartilage and bones, or between teeth and bones.– When two bones articulate

with one another we say that the 2 bones form a joint.

• Arthrology = study of joints• Kinesiology = study of

movement within the human body

• Rheumatology = study of joint diseases and related conditions

Joint Strength, Flexibility, & Movement

• Determined by:– Shape of the articulating

bones– Flexibility of the ligaments

that attach bone to bone– Tension of tendons and

muscles of the articulating bones

– Hormones• Dislocation: When

articulating bones move from their normal positions.

Joint Structure• Classification:– Type of connective

tissue that holds the bones together.

– The presence or absence of a synovial cavity (space between the articulating bones).

Joint Function

• Types:– Synarthrosis = Immoveable joint

• Ex. pelvis , sutures, teeth

– Amphiarthrosis = Slightly moveable joint• Ex. epiphysis, tibia-fibula, vertebrae and pelvic symphysis

– Diarthrosis = A freely movable joint. • All synovial joints fall into this category• Come in many shapes • Allow for different types of movements

• Classification:– Relates to the amount of

movement allowed

Types of Fibrous Joints

1. Suture• Unite the bones of the skull• The irregular interlocking edges decrease chances of

fracturing• Functionally classified as Synarthrosis = Immovable

• Fibrous joints are held together by fibrous connective tissue – bones lack a synovial cavity = little to no movement.

Types of Fibrous Joints2. Syndesmosis

• Contains dense fibrous connective tissue

• Functionally classified as amphiarthrosis = Slight movement

• Ex. The distal articulation between the tibia and the fibula.

Types of Fibrous Joints3. Gomphosis• Cone shaped peg that

fits into a socket• The only found in the

articulations of the roots of the teeth with the sockets of the mandible & maxillae.

• Functionally classified as synarthrosis = Immovable

Types of Cartilaginous Joints

1. Synchondrosis• A cartilage joint that

connects with hyaline cartilage

• Ex. Epiphyseal plate that connect the epiphysis and the diaphysis of a bone.

• Functionally classified as synarthrosis = Immovable

• Cartilagious joints are held together by fibrocartilage or hyaline cartilage • Bones lack a synovial cavity

Types of Cartilaginous Joints1. Symphysis• A cartilage joint where ends of

the articulating bones are covered with hyaline cartilage, but the bones themselves connect via fibrocartilage.

• Ex. Pubic symphysis & between the bodies of vertebrae.

• Functionally classified as amphiarthrosis = Slightly movable

Types of Synovial Joints• Synovial joints

– Presence of a synovial cavity

– Functionally classified as diarthrosis = Freely movable

– Epiphysis of bones are covered by articular (hyaline) cartilage– Reduces friction – Absorb shock

– Contain ligaments: bundled fibers that connect bone to bone and give joints stability

Types of Synovial Joints1. Planar AKA Plane or Gliding Joint• Flat or slightly curved bones• Allow for side to side & back

and forth gliding motion

2. Hinge Joint• Concave surface meets the

convex surface of another bone• Allow for opening & closing

motion like the hinge of a door

Types of Synovial Joints3. Pivot Joint• A rounded surface articulates

with a ring formed by another bone or ligament.

• Allows for rotation around its vertial axis.

4. Condyloid Joint • Convex-oval shape of one

bone fits into the concave-oval shape of another.

• Allows for up & down and side to side movement.

Types of Synovial Joints5. Saddle Joint• Allows for side to side and

back to forth movement.

6. Ball & Socket Joint• Ball like surface of one

bone fits into the cup like depression of another.

• Allows for free movement.

Joint Review Video (click picture)