Joints

Part 2: Support & Movement

Joints

Joints or Articulations: Locations were bones join together that allow for some degree of movement.

Arthrology: The scientific study of Joints! Most important joints for this test: Knee

and Shoulder Classification: Either by structure or

range of movement allowed.

Structural Classifications

Synovial Joints: The most important type; found throughout the body and named for their synovial cavity that is lubricated by the synovial fluid. Freely movable jointsBones joined together by dense irregular

connective tissue within the fibrous joint capsule

Primary examples: Elbow, knee, hip, ankle

Structural Classifications

Fibrous Joints: Joints where the bones are held together via collagenous fibers running from the matrix of one bone to the matrix of the other bone.NO joint cavity; little to no movement

Structural Classifications

Types of Fibrous Joints: Sutures: Found only in the bones of the skull

Irregular edges provide added strength against fractures. Synostosis or Bony Joint: When a suture is replaced by

bone.

Syndesmosis: More fibrous tissue than a suture, but permits a very small degree of movement

Examples: Distal tibiofibular joint

Gomphoses: A cone-shaped peg fitting into a socket. ONLY found where teeth attach.

Sutures

Syndesmosis

Gomphoses

Structural Classification

Cartilaginous Joints: Bones are held together by hyaline or fibro cartilage.DO NOT contain a joint cavity. Allow little to no movement.

Structural Classification

Types of Cartilaginous Joints: Synchondroses: Made of hyaline cartilage.

Found in epiphyseal plates connecting the epiphysis and diaphysis of growing bone

Found where the rib attaches to the sternum

Symphyses: A flat disk of fibrocartilage connects the bones

Found in the public symphysis or the intervertebral joints

Slightly moveable

Synchondroses Symphyses

Functional Classification

Diarthroses: Freely moveable synovial jointsEx. Shoulder, hip, finger, knee

Amphiarthrosis: Slightly moveable jointsEx. Symphysis pubis and intervertebral discs

Synarthroses: Immovable jointsEx. Sutures, epiphyseal plates of long bones

Diarthroses

Amphiarthrosis

Synarthroses

Synovial Joints

Bones covered by articular cartilage, which reduces friction between bones & absorbs shock

Articular Capsule: Surrounds each synovial joints, composed of… Fibrous Capsule: An outer layer Synovial Membrane: Inner layer; secretes synovial

fluid Synovial Fluid: Reduces friction, supplies nutrients,

contains phagocytes to help remove debris from the joint

Meniscus: Cushy pad contained by some joints to further absorb shock

Synovial Joints

Ligaments: Tough connective tissue bands arranged in capsule bundles. Run from bone to bone across the joint. Helps stabilize and strengthen the joint

Bursae: Fluid-filled sacs beneath the muscles Help tendons glide easily over joints Bursitis: Inflammation of the bursae from

overexertion of a joint Tendon Sheaths: Thin membrane enclosing the

tendon. Help reduce friction at joints.

Types of Synovial Joints

Ball-And-Socket Joints: Highly moveable Multiaxial Examples: Shoulder &

hip joints

Types of Synovial Joints

Planar Joints: “Gliding Joints” Permit some side-to-side &

back-and-forth movement Nonaxial Examples: Joints between

carpal & tarsal bones & between the scapula and clavicle

Types of Synovial Joints

Pivot Joints: Where a projection on one bone fits into a ring shaped ligament on the other bone. Uniaxial (allows for

rotationa round one axis only)

Examples: Atlanto-axial joint (allows side-to-side head shakes) & where the radius articulates to the ulna.

Types of Synovial Joints

Hinge Joints: Act like a hinge on a door Allow for uniaxial or

monoaxial swinging motion

Examples: Knee, elbow, ankle, finger, toe joints

Types of Synovial Joints

Condyloid Joints: Occur where an oval convex surface fits into a similar shaped concave depress on the next bone. Biaxial Examples:

Metacarpophalangeal joints of the wrist.

Types of Synovial Joints

Saddle Joint: Named for its shape Biaxial Only ONE: Where the

thumb metacarpal articulates with the trapezium of the wrist

Allows for the opposable thumb

Joint Movement

Flexion: Movement that decreases the angle of the bone in a joint Example: Bending

your arm at the elbow toward you

Flexing the knee to limb stairs

Joint Movement

Extension: Movement that increases the angle of a joint or straightens the joint, returning it to its anatomical position. Example:

Straightening your arm back out.

Joint Movement

Hyperextension: Extension of a joint beyond 180 degrees Example: Tilting your

head back to look up at the ceiling

Joint Movement

Abduction: Movement of a body part away from the midline Example: Raising the

humerus (upper extremity) laterally at the shoulder

Joint Movement

Adduction: Movement of a body part toward the midline Example: Pulling your

thighs together or moving the humerus back to the anatomical position

Joint Movement

Circumduction: Movement in which one end (usually the proximal end) of an appendage stays relatively stationary while the other end (usually distal) makes a circular motion Example: Making a

windmill motion with the arm

Joint Movement

Rotation: Movement in which a bone revolves around its longitudinal axis Example: Twisting at

the waist or turning your head from side to side

Joint Movement

Depression: Movement that lowers a bone vertically Example: Opening the

mouth

Elevation: Movement that raises a bone vertically Example: Closing the

mouth

Joint Movement

Protraction: Movement of a bone anteriorly Example: Jutting your chin

out

Retraction: Movement of a bone posteriorly Example: Pulling your chin

back in after jutting it out

Joint Movement

Supination: Rotating the arm palm upward.

Pronation: Rotating the hand palm downward

Joint Movement

Inversion: When the soles of the feet turn medially to face each other.

Eversion: Turns the soles of the feet laterally to face away from each other.

Joint Movement

Dorsiflexion: The act of pointing the toes upward.

Plantar Flexation: Pointing the toes downward.

Joint Movement

Opposition: When the thumb reaches across the palm to touch the fingers Useful for grasping &

manipulating objects

Joint Movement

A great webside that goes through all the types of joint movement for each major joint…

http://www.brianmac.co.uk/musrom.htm