Learning objectives

Joints

Learning objectives

1. Explain how joints can be classified according to the type of tissue that binds the bones together and the degree of movement possible at the joint.

2. Describe how bones of fibrous joints are held together, and name an example of each fibrous joint.

3. Describe how bones of cartilaginous joints are held together, and name an example of each type of cartilaginous joint.

4. Describe the general structure of a synovial joint.

5. Distinguish among the six types of synovial joints and name an example of each type.

6. Explain how skeletal muscles produce movements at joints, and identify several types of joint movements.

7. Describe the shoulder joint and explain how its articulating parts are held together.

8. Describe the elbow, hip, and knee joints and explain how their articulating parts are held together.

9. Describe life-span changes in joints.

tutorial outline

A. Arthrology – science of joints.

B. Articulation, or joint – functional junction between bones

II. Types of Joints

A. Structural Classification

1. fibrous – composed of dense connective tissue

2. cartilaginous – composed of cartilage

3. synovial – contains a synovial membrane

B. Functional Classification

1. synarthrotic – no movement

2. amphiarthrotic – slightly moveable

3. diarthrotic – fully moveable

III. Fibrous Joints

A. Suture

1. Joins bones of the skull (sutural ligaments)

2. Synarthrotic (immovable)

B. Syndesmosis

1. bones connected by an interosseous ligament or membrane

2. includes the distal tibiofibular joint, and intermediate radioulnar joint at the wrist

3. amphiarthrotic

C. Gomphosis

1. dental-alveolar joint

2. periodontal membrane (ligaments) anchors the tooth to socket (dental alveoli)

3. chronic dental problems or bone resorption may loosen the ligaments, resulting in bone loss

4. synarthrotic

IV. Cartilaginous Joints

A. Synchondrosis

1. Bones are connected by a plate of hyaline cartilage

2. Examples include joint between first rib and manubrium

3. Also includes the epiphyseal plates in developing bones

a. epiphyseal plates eventually ossify (once ossified, the joint is called synostosis)

4. Synarthrotic

B. Symphysis

1. Pad or plate of fibrocartilage between bones

2. Compressible “shock absorber”

3. Examples include pubic symphysis and intervertebral discs

a. Annulus fibrosus = outer ring of fibrocartilage

b. Nucleus pulposus – inner gelatinous core

• 
  Herniated disc occurs when annulus fibrosus ruptures, causing the nucleus pulposus to “slip” out of the intervertebral disc, compressing the spinal nerve.
  

A. General Structure

1. Articular cartilage – hyaline cartilage covering the surface of each bone

2. Joint Capsule – dense CT capsule surrounding the joint cavity.

3. Synovial Membrane

• 
  Loose CT membrane covering internal joint surfaces, excluding the articular cartilage
  
• 
  Secretes synovial fluid (viscous, egg-white consistency)
  

5. Synovial Cavity – potential space between bones, filled with synovial fluid

6. Bursa – synovial membranous sac of synovial fluid located outside the joint capsule

• 
  Prevents friction between joint and adjacent structures (bone, skin, tendons, ligaments, etc.)
  

8. Ligaments – reinforce and protect the joint

VI. Types of Synovial Joints

A. Ball-and-socket Joints

1. ball-shaped head fits into the socket of another bone

2. examples: shoulder and hip joints

3. multiaxial - most freely movable of all joints

B. Condylar joints

1. Oval-shaped head fits into elliptical socket

2. Examples include the wrist and metacarpophalangeal joints

3. Biaxial – permits all movements except rotation

C. Hinge Joints

1. Permits only flexion/extension

2. Examples include: humeroulnar joint, knee (modified hinge), interphalangeal joints

D. Pivot joints

1. permit rotation around a central axis

2. examples include atlantoaxial joint and proximal radioulnar joint

E. Gliding (plane) joint

1. surface of bones glide across each other

2. examples include between carpals and patellofemoral joint

F. Saddle Joint

1. carpometacarpal joint of the thumb

2. abduction/adduction flexion/extension opposition

VII. Joint Movements

A. Flexion – decreases angle of joint

B. Extension – increases angle of joint

C. Hyperextension – increases angle of joint beyond anatomical position

D. Rotation – movement around a central axis (medial rotation/lateral rotation)

E. Circumduction – moving the end of a bone in a circular motion

F. Abduction – movement away from the midline

G. Adduction – movement toward the midline

H. Pronation – rotation of forearm so palms face downward or posteriorly

I. Supination – rotation of forearm so palms face upward or anteriorly

J. Protraction – movement in the anterior plane

K. Retraction – movement in the posterior plane

L. Elevation – movement upward (superiorly)

M. Depression – movement downward (inferiorly)

N. Dorsiflexion – movement at the ankle that points toes upwards

O. Plantar flexion – movement at the ankle that points toes downwards

P. Eversion – movement at the ankle that points sole laterally

Q. Inversion – movement at the ankle that points sole medially

R. Opposition – combination of flexion, adduction, and circumduction of thumb that brings the tip of the thumb in contact with tips of slightly flexed fingers

VIII. Joint Disorders

A. Sprain – overstretching or tearing of a ligament

B. Bursitis – inflammation of a bursa

C. Arthritis – inflamed, swollen, painful joints

• 
  Most common form of arthritis
  
• 
  Occurs with aging
  
• 
  Articular cartilage wears down causing movement to occur bone-against-bone
  
• 
  Often induced by an injury – blow to the joint produces intense persistent pain
  
• 
  Fingers may become gnarled, knee may bulge
  

• 
  Autoimmune disease – immune system attacks healthy cells
  
• 
  The joint becomes inflamed and thickened, forming a mass of connective tissue, called a pannus that invades the joint.
  
• 
  The joint may ossify fusing the bones