Chapter 8Joints

Lecture #17, 18

Objectives:1. Define joint or articulation

2. Describe synarthrotic joints. Name and give an example of the fibrous and cartilaginous types.

3. Describe amphiarthrotic joints. Name and give an example of the fibrous and cartilaginous types.

4. Describe the structural characteristics shared by all diarthrotic or synovial joints.

5. Name 6 types of diarthrotic joints based on the movement(s) allowed. Provide examples of each.

6. Compare and contrast the common types of arthritis and identify common joint injuries.

Joints/Articulations: places where two or more bones come together. SEE TABLE 8.1

Synarthrosis: immovable joint

I. Fibrous: no joint cavity present; ex. suture SEE FIGURE 8.1a

II. Cartilaginous: articulating bones united by cartilage; ex. synchondrosis (at epiphyseal plate) SEE FIGURE 8.2a

Amphiarthrosis: slightly movable joint

I. Fibrous: bones connected by ligament (tibia/fibula, radius/ulna); ex. syndesmosis SEE FIGURE 8.1b

II. Cartilaginous: two bones with a cartilage pad in between (pubic symphysis, intervertebral discs); ex. symphysis SEE FIGURE 8.2c

Diarthrotic/Synovial: freely movable joint where articulating bones are separated by a fluid-filled joint cavity. SEE FIGURE 8.3

I. Articular cartilage: hyaline cartilage that covers the ends of bones

II. Joint cavity: space filled with fluid

III. Articular or joint capsule: D.I.C.T. surrounding joint cavity, connected to periosteum, lined with synovial membrane of areolar connective tissue

IV. Synovial fluid: capillaries from synovial membrane produce fluid, a “weeping” lubrication

V. Reinforcing ligaments: hold bones together; patellar ligament, anterior/posterior cruciate ligaments

VI. Meniscus: fibrocartilage pad between condyles of femur and tibia of knee for extra cushioning.

VII. Bursae and tendon sheaths: flattened fibrous sacs or sacs that wrap around tendons (like hot dog bun); provide extra protection under ligaments (bursae) or around tendons. Bunions @ base of big toe. SEE FIGURE 8.4

Types of Diarthrotic Joints SEE FIGURE 8.7

I. Gliding/plane: intercarpal/intertarsal; articular processes of vertebrae

II. Hinge: move in single plane; humerus/ulna, interphalangeal joint

III. Pivot: rotational movement: atlas/odontoid process of axis, radius/humerus

IV. Condyloid: oval articulating surfaces; radius/carpals, metacarpal/phalangeal, femur/tibia

V. Saddle: concave surfaces (saddle shaped); metacarpal/carpal joint below thumb

VI. Ball and socket/rotator cuff: head in tendonous or bony socket; os coxa/femur, scapula/humerus. Shoulder made of rotator cuff muscles which are: Supraspinatus, Infraspinatus, Teres minor, Subscapularis

Common joint injuries

  1. Sprain: ligaments stretched or torn
  2. Cartilage injuries: tearing knee menisci
  3. Dislocations: position outside normal planes of movement
  4. Bursitis/tendonitis: inflammation of tendon sheath or bursa

Arthritis

I. Osteoarthritis: wear and tear on joint articular cartilage, bone thickens, bony spurs may develop, friction and inflammation occurs

II. Rheumatoid arthritis: autoimmune disease involving inflammation of synovial membrane, joints become swollen, inflammatory cells migrate to site, membrane thickens, scar tissue develops called a pannus See Figure 8.15

III. Gouty arthritis: accumulation of uric acid crystals in joint tissues

Body Movements SEE FIGURE 8.5/8.6

I. Flexion: decrease the angle of a joint (bending the elbow)

II. Extension: increase the angle of a joint, up to 180° (straightening the elbow)

III. Hyperextension: increase angle beyond 180° (bending head backwards)

IV. Dorsiflexion: pointing toe upward

V. Plantar flexion: pointing toe downward

VI. Abduction: moving a limb away from the midline of the body

VII. Adduction: moving a limb toward the midline of the body

VIII. Circumduction: circling the arm or leg, as if drawing the circumference of a circle

IX. Rotation: turning arm, leg, or head out, then in, or from side to side.

X. Supination: a special form of rotation where forearms are turned palm up.

XI. Pronation: a special form of rotation where forearms are turned palm down.

XII. Inversion: turning the sole of the foot inward (like checking for gum!)

XIII. Eversion: turning the sole of the foot outward (like checking the other way)

XIV. Protraction: sticking out the lower jaw

XV. Retraction: moving the lower jaw back into normal position