1. Joints of the Body

2. Definition Joints are junctions between bones
A joint is the point of contact, or articulation, between two bones
Joints hold bones together
Many of them permit flexibility and movement

3. How Joints Are Held Together
Both ligaments and tendons help to hold joints together
Ligaments – connect bones to bones
Tendons – connect muscle to bone
Joints are also surrounded and held together by thick connective tissue called a capsule, which is a lot like Saran-Wrap
Joints are cushioned by bursae
Bursa sacs are fluid-filled sacs that keep tendons and ligaments from rubbing against bony processes, which could cause shredding and tearing, as well as bony irritation

4. Classification of Joints
Joints are classified according to the degree of movement that they permit
3 categories
Synarthroses (sin’-ar-throw’-sees)
Amphiarthrosis (am’-fee-ar-throw’-sees)
Diarthroses (dye’-ar-throw’-sees); also known as synovial joints

5. Synarthroses Joints Do not permit movement
Bones are connected by a thin layer of fibrous connective tissue that may be replaced by bone in the adult
Example: The sutures that join skull bones are synarthroses

6. Amphiarthroses Joints
Permit slight movement and help absorb shock
Bones are joined by cartilage
Example: The pubic symphysis of the pelvis and the intervertebral joints of the vertebral column

7. Diarthroses (Synovial) Joints
Referred to as freely movable joints, though the amount of flexibility varies
Most of the body’s joints are diarthroses
6 types
Gliding
Condyloid
Saddle
Pivot
Hinge
Ball-and-socket

8. Make-up of a Diarthrosis Joint
Ends of bones that form these joints are covered with hyaline (articular) cartilage, which lacks nerves and blood vessels
The joint is surrounded by a connective tissue capsule, called the joint capsule
Made of tough, fibrous connective tissue that is continuous with the covering of the bone
The joint capsule is reinforced with ligaments, which connect the bones, and limit movement at the joint

9. Make-up, continued
The joint capsule is lined with a membrane that secretes a lubricant called synovial fluid
Reduces friction during movement and absorbs shock
Fluid-filled sacs called bursae are located between bone and tendons and between bone and some other tissues to cushion the movement of the bone over other tissues

10. Gliding Joints Shape: Flat or slightly curved
Range of movement: One bone glides over another without circular movement
Example: Carpal joints of wrist and tarsal joints of ankle

11. Condyloid Joints
Shape: Oval-shaped condyle fits into elliptical cavity
Range of movement: Angular movement
Example: Joints between metacarpals and phalanges

12. Saddle Joints Shape: Saddle shaped
Range of movement: Permits wide range of movement
Examples: Carpo-metacarpal joint of thumb

13. Pivot Joints
Shape: Small projection of one bone pivots in ring-shaped socket of another bone
Range of movement: Rotation
Example: Atlanto-axial joint of 1st & 2nd cervical vertebrae; radio-ulnar joint of elbow

14. Hinge Joints
Shape: Convex surface of one bone fits into concave surface of another bone
Range of movement: Motion in one plane only; permits only flexion and extension
Examples: Elbow; knee

15. Ball-and-Socket Joints
Shape: Ball-shaped end of one bone fits into cup-shaped socket of another bone
Range of movement: Permits widest range of movement, including rotation
Examples: Shoulder; hip joint

16. Naming Joints
Joints are named according to the 2 structures that are being joined
Examples:
The clavicle joins with the acromion process on the scapula
This is called the acromio-clavicular joint (a-c joint)
Carpals join with metacarpals
Called the carpo-metacarpal joints
Metacarpals join with phalanges
Called the metacarpo-phalangeal joints (MP joints)
Phalanges join with each other
Called interphalangeal joints (IP joints)

17. A Few Things To Remember
Hip ball-and-socket joint
Femoral head (ball) fits into
Acetabulum of the ischium (socket)
Shoulder ball-and-socket joint
Humeral head (ball) fits into
Glenoid fossa of the scapula (socket)
Called the “gleno-humeral joint”
Jaw joint – saddle joint
Mandible fits into
Temporal bone
Called the temporo-mandibular joint (TMJ)