1. Articulations or Joints
Articulation or Joint
Place where two bones (or bone and cartilage) come together
Arthrology = study of the joints
Functions of joints
Give the skeleton mobility
Hold the skeleton together
Structure correlated with movement

2. Classification of Joints
Structural classes: based on type of connective tissue type that binds bones and whether or not a joint cavity is present
Fibrous
Cartilaginous
Synovial
Functional classes: based on degree of motion
Synarthrosis: non-movable
Amphiarthrosis: slightly movable
Diarthrosis: freely movable

3. Fibrous Joints Characteristics Types:
United by fibrous connective tissue
Have no joint cavity
Move little or none
Types:
Sutures
Syndesmoses

4. Fibrous Joints: Syndesmoses
Two bones joined by ligament
Most moveable of fibrous joints
Examples: radioulnar joint and tibiofibular joints

5. Cartilaginous Joints Bones are joined by cartilage Lack a joint cavity
Types
Synchondroses: bound by hyaline cartilage
Symphyses: bound by fibrocartilage

6. Cartilaginous Joints: Synchondroses
Joined by hyaline cartilage
Little or no movement
Some are temporary and are replaced by synostoses
Some are permanent
Some like costochondral joints develop into synovial joints
Examples: Epiphyseal plates, 1st sternocostal

7. Cartilaginous Joints: Symphyses
Fibrocartilage uniting two bones
Slightly movable
Examples: symphysis pubis, between the manubrium and the body of the sternum, intervertebral disks.

8. Synovial Joints
Contain synovial fluid in a joint cavity called the synovial cavity
Allow considerable movement (diarthroses)
Most joints that unite bones of appendicular skeleton reflecting greater mobility of appendicular skeleton compared to axial

9. Structure of Synovial Joints
Articular cartilage:
Hyaline cartilage that covers epiphysis
Absorbs compression of joint
Joint cavity (synovial cavity)
Unique to synovial joints
Cavity is a potential space that holds small amount of fluid
Synovial fluid:
Viscous fluid similar to raw egg white
A filtrate of blood from capillaries in synovial membrane
Contains glycoprotein molecules secre-ted by fibroblasts
Nerves in capsule help brain know position of joints (proprioception)
Structure of Synovial Joints

10. Flexion and Extension
Flexion: movement of a body part anterior or posterior to the coronal plane
Extension: movement of a body part posterior or anterior to the coronal plane
Dorsoflexion - foot lifted toward the shin
Plantar flexion - pointing toes downward
Abduction: movement away from the midline
Adduction: movement toward the midline

11. Types of Synovial Joints: Plane Joints
Plane or gliding joints
Monaxial. One flat bone surface glides or slips over another similar surface
Sometimes considered an amphiarthrosis
Examples: intervertebral, intercarpal, intertarsal acromioclavicular, carpometacarpal, tarsometatarsal,

12. Hinge and Pivot Joints Hinge joints Pivot joints Monaxial
Convex cylinder in one bone; corresponding concavity in the other
Example: elbow, ankle, interphalangeal
Pivot joints
Monaxial. Rotation around a single axis.
Cylindrical bony process rotating within a circle of bone and ligament
Example: articulation between dens of axis and atlas (atlantoaxial), proximal radioulnar

13. Types of Synovial Joints:
Saddle joints
Each articular surface is shaped like a saddle;
Trapeziometacarpal joint at base of the thumb

14. Ball-and-Socket and Ellipsoid Joints
Smooth heispherical head fits within a cuplike depression
Multiaxial
Examples: shoulder and hip joints
Condyloid (ellipsoid) joint
Oval convex surface on one bone fits into a similarly shaped depression on the next
Atlantooccipital joint (C1-C2)
Metacarpophalangeal joints

15. The Knee Joint Most complex diarthrosis
patellofemoral = gliding joint
tibiofemoral = gliding with slight rotation and gliding possible in flexed position
Joint capsule anteriorly consists of patella and extensions of quadriceps femoris tendon
Capsule strengthened by extracapsular and intracapsular ligaments

16. Effects of Aging on Joints
Tissue repair slows; rate of new blood vessel development decreases
Articular cartilages wear down and matrix becomes more rigid
Production of synovial fluid declines
Ligaments and tendons become shorter and less flexible: decrease in range of motion (ROM)
Muscles around joints weaken
A decrease in activity causes less flexibility and decreased ROM