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

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 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/ gliding joints - movement limited, either up/down or left/right, ex: sternum/ clavicle, between vertebrae, carpals, tarsals 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 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

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