Joints Articulations Joints Articulations are where 2 or

Joints = Articulations

Joints • Articulations are where 2 or more bones meet.

Classification of Joints

Classified according to movement or function: 1. synarthroses immovable • ex: cranial bones, sutures

2. amphiarthroses - slightly movable ex: ribs with vertebrae

3. diarthroses – freely movable ex: elbow, knee

sutures only between bones of the skull • a type of fibrous joint joined by fibrous tissue

Synovial Joints

Synovial Joints • articulating bones are separated by a fluid-filled cavity • all are freely movable

Synovial Joints Structure: articular cartilage smooth, hyaline joint cavity – fluid-filled space articular capsule double fibrous membrane synovial fluid prevents cartilage erosion, lubricates reinforcing ligaments

• Bursa - between bone and ligaments, muscle, skin, or tendons - flattened fibrous sacs - prevents rubbing against bone

• tendons – connect muscle to bone, fibrous tissue

• ligaments – connect bone to bone, fibrous tissue

Types of Synovial Joints

• hinge - single plane motion ex: knee, elbow, fingers

• pivot – rotation ex: atlas and axis, radioulna

• saddle - move in 4 directions ex: carpalmetacarpal of thumb only

• ball and socket movement in all axis ex: shoulder, hip

• Plane or gliding joints movement limited, either up and down or left and right ex: sternum and clavicle, between vertebrae, carpals, tarsals

• condyloid – angular motion ex: knuckles

Types of Synovial Joints 1. hinge - single plane motion, ex: knee, elbow, fingers 2. pivot - rotation, ex: atlas and axis, radioulna 3. saddle - move in 4 directions, ex: carpalmetacarpal of thumb only 4. ball and socket - movement in all axis, ex: shoulder, hip 5. plane/ gliding joints - movement limited, either up/down or left/right, ex: sternum/ clavicle, between vertebrae, carpals, tarsals 6. condyloid - angular motion, ex: knuckles

Types of Angular Movements

• flexion - decreases angle, brings bones together dorsiflexion - foot up (toes up)

extension - increases angle hyperextension - beyond upright position (head), exception knee towards back of body

• abduction - away from midline • adduction - toward midline

• circumduction - distal end moves in circle, throwing a baseball

• rotation - around own axis, turning head

Types of Angular Movements 1. flexion - decreases angle, brings bones together 2. dorsiflexion - foot up (toes up) 3. extension - increases angle 4. hyperextension - beyond upright position (head), exception knee towards back of body 5. abduction - away from midline 6. adduction - toward midline 7. circumduction - distal end moves in circle, throwing a baseball 8. rotation - around own axis, turning head

Joint Injuries

Sprains • ligaments stretched or torn • heals slowly because of poor vascularity • if completely torn, must be repaired surgically

Dislocations • when bones are forced out of normal position of joint cavity • bone ends must be reduced (realigned) like a fracture

Cartilage Injuries • most are tearing of knee menisci from fall or severe twisting • cartilage is avascular and will not be able to repair itself

• arthroscopy allows surgeon to view interior of joint through small incision – damaged cartilage is removed, ligament repaired – does not severely impair movement but joint less stable