Joints

Kinesiology

study of movement

Arthology is the study of

joints

joint

A place in the body where two bones come together

• links bones of skeletal system

function of joints

• permits movement

-protects soft organs

How are joints classified?

functionally and structurally

Synathorosis joint

bones are very close together, joint interlocks allowing for NO MOVEMENT , STRONG

Where are synarthrosis joints found?

sutures, gomphosis, synchondrosis

ampiarthrosis joint

joints permit little movement but not freely movable

• connected b y collagen or cartilage

diarthrosis joint

freely movable joint, WEAK

bony joint (synostosis)

an immobile joint formed when the gap between two bones ossifies, and the bones become, in effect, a single bone

fibrous joints

consists of inflexible layers of dense connective tissue, holds the bones tightly together

Sutures

Areas where the cranial bones have joined together

Gomphosis

attachment of a tooth to its socket

Syndesmosis

bones united by fibrous connective tissue, forming an interosseous membrane or ligament

cartilaginous joints

bones held together by cartilage

Synchondrosis

an almost immovable joint between bones bound by a layer of cartilage, as in the vertebrae.

symphysis

two bones joined by fibrocartilage

synovial joints

two bones are joined by an encapsulated joint (joint cavity), freely movable

what are the planes of movement of synovial joints?

abduction (away), adduction (towards), extension (open), flexion (close), and rotation.

Components of a synovial joint

(1)joint capsule (2)articular cartilages (3) joint cavity filled with synovial fluid (4)synovial membrane lining joint capsule (5) accessory structures and (6) sensory nerves and blood vessels that supply the exterior and interior of the joint

articular cartilage

layer of hyaline cartilage usually 2 or 3 mm thick that covers the facing surfaces of two bones.

joint (articular) cavity

A space between the articulating bones. The cavity is filled with synovial fluid

synovial fluid

slippery lubricant in the joint cavity. Makes the movement of synovial joints almost friction-free

joint (articular) capsule

connective tissue that encloses the cavity and retains the fluid

outer fibrous capsule (part of articular capsule)

continuous with periosteum of adjoining bones

inner, cellular, synovial membrane (part of articular capsule)

composed mainly of fibroblast-like cells that secrete synovial fluid and macrophages that remove debris from the joint cavity

Meniscus

moon-shaped cartilage in the knee

What does the meniscus do?

1.) absorbs shock and pressure

2.) guides bones across each other

3.) improves their fit together

4.) stabilize the joints, reducing the chance of dislocation.

articular disc

forms a pad between articulating bones that crosses the entire joint capsule

Tendon

strip of collagenous tissue attaching muscle to bone

ligament

a strip of collagenous tissue attaching one bone to another

bursa

Synovial-filled sac between muscles, tendons, or skin and bone.

What does the bursa do?

Cushions and aid tendon movement, alter pull direction

tendon sheath

elongated bursa that wraps around a tendon

What is a lever in relation to joint?

any elongated, rigid object that rotates around a fixed point called a fulcrum

• Long bones act as levers to enhance the speed or power of limb movements

Mechanical Advantage (MA)

Ratio of the output force exerted by a machine to the input force applied to the machine.

if the lever(bone) produces more force, then what?

there will be less speed or distance

if the lever (bone) produces more speed or distance, then what?

there will be less force

fulcrum

axis of rotation and fixed point on a lever

first class lever

The fulcrum is positioned between the effort and resistance

second class lever

the resistance is between the fulcrum and the effort

third class lever

the effort is between the fulcrum and the resistance

ROM (range of motion) is determined by

• Structure of the articular surfaces

• Strength and tautness of ligaments and joint capsules

• Action of the muscles and tendons

monoaxial (axes of rotation)

movement in one plane e.g., elbow

biaxial (axes of rotation)

movement in two planes e.g., wrist

triaxial (axes of rotation)

Movement in three planes e.g., shoulder, hip.

multiaxial (axes of rotation)

movement in multiple planes e.g., hip, shoulder

classes of synovial joints

ball-and-socket, condylar, saddle, plane, hinge, pivot

ball and socket synovial joint

Smooth, hemispherical head fits within a cup-like socket

• shoulder/hip

• angular, circumduction and rotation

• triaxial

pivot synovial joint

A bone spins on its longitudinal axis

• radioulnar joint at the elbow

• rotation/monaxial

hinge synovial joint

One bone with a convex surface fits into a concave depression of another bone

• elbow, knee, joints within fingers, toes

• angular monaxial

plane synovial joint

Flat articular surfaces, and bones slide over each other

• between carpal bones of the wrist; between tarsal bones of the ankle

• gliding/slight nonaxial or multiaxial

condylar synovial joint

The oval convex surface of one bone fits into a complementary-shaped depression on the other

• radiocarpal joint/ metacarpophalangeal joints

• angular/ biaxial

saddle synovial joint

: Both bones have an articular surface that is shaped like a saddle, one concave, the other convex

• trapeziometacarpal (opposable thumb)

• angular/ biaxial

Flexion

decrease joint angle

Extension

increases the angle of a joint

Hyperextension

extension of a joint beyond the zero position

lateral flexion

involves bending a body part, mainly your torso and neck, sideways

Abduction

movement of a body part in the frontal plane away from the midline of the body

Adduction

movement in the frontal plane back toward the midline

Elevation

movement that raises a body part vertically in the frontal plane

Depression

movement that lowers a body part in the same plane

Protraction

the anterior movement of a body part in the transverse (horizontal) plane (forward)

Retraction

posterior movement (backward)

Circumduction

one end of an appendage remains stationary while the other end makes a circular motion

medial rotation

rotational movement towards the midline

lateral rotation

rotation away from the midline

Supination

movement that turns the palm up or anteriorly

Pronation

turning the palm downward or posteriorly

lateral excursion

right or left movement from the zero position

medial excursion

movement back to the median, zero position

ulnar flexion

tilts the hand toward the little finger

radial flexion

tilts the hand toward the thumb

flexion of fingers

curling fingers

extension of fingers

straightening fingers

radial abduction

moving thumb away from index finger

palmar abduction

moving thumb away from hand and pointing it anteriorly