Classification and Type of Joints

Classification of Joints

-STRUCTURAL

•Based on material binding bones together

•Three structural classifications: Fibrous joints, Cartilaginous joints, Synovial joints

-FUNCTIONAL

•Based on amount of movement joint allows

•Three functional classifications:Synarthroses = immovable, Amphiarthroses = slightly movable,

Diarthroses = freely movable

Fibrous Joint

-Bones are joined by dense fibrous connective tissue

-No joint cavity

-Mostly synarthrotic (immovable) but that depends on length of connective tissue fiber

Three types:

-Sutures=skull

-Syndesmoses=between radius and ulna

-Gomphoses= between socket and periodontal ligaments of teeth

Cartilaginous Joints

-Bones united by cartilage

-No joint cavity

-Not highly movable

-Two types: Synchondrosis and Symphysis

Location, structure, function

-Synchondrosis: Bones are joined by hyaline cartilage, location (rib attachment to sternum), function:

epiphyseal plate(temporary hyaline cartilage) in children binds epiphysis and diaphysis, Structure is

non-moveable

-Symphysis: •2 bones joined by fibrocartilage, located at pubic symphysis and intervertebral discs.

Bones are slightly moveable

Synovial Joints Unique Features

—Articular capsule: Two layers i. External Fibrous layer of Dense Connective Tissue ii. Inner Synovial

membrane of Areolar & Epithelial Tissue

—Articular cartilage (hyaline cartilage): i. Prevents crushing of bone ends ii. Cushions the epiphysis

—Synovial fluid : i. Viscous slippery filtrate of plasma and hyaluronic acid ii. Lubricates and nourishes

articular cartilage iii. Contains phagocytic cells to remove microbes and debris

— Reinforcing ligaments: Found inside and outside the capsular space

—Nerves and sparse blood vessels: i. Nerve fibers detect pain ii. monitor joint position and stretch iii.

Capillary beds supply filtrate for synovial fluid

Types of synovial joints and locations

—Gliding or Plane Joints

•Intercarsal or intertarsals

•Non axial joint

•Considered amphiarthroses.

—Hinge Joints

•ulna and humerus at elbow joint

•femur and tibia at knee joint

•Phalangeal joints

—Pivot Joints

•One bone has a projection that fits into a ringlike ligament of another

•First bone rotates on its longitudinal axis relative to the other

•atlantoaxial joint (dens and atlas)

•proximal radioulnar joint allows the radius during pronation and supination

•Diarthrosis

—Condylar (ellipsoidal) and Saddle Joints.

•radiocarpal joint of the wrist

•metacarpophalangeal joints at the bases of the fingers

•trapeziometacarpal joint at the base of the thumb

—Ball and Socket Joints

•head of humerus into glenoid cavity of scapula

•head of femur into acetabulum of hip bone

Movement terms

-Flexion decreases the angle of a joint

-Extension straightens and returns to the anatomical position

-Hyperextension = extension beyond 180 degrees

-Abduction is movement of a part away from the midline

-Adduction is movement towards the midline

-Circumduction is movement in which one end of an appendage remains stationary while the other

end makes a circular motion

-Rotation: Movement on longitudinal axis(trunk, thigh, head or arm).Medial rotation turns the bone

inwards. Lateral rotation turns the bone outwards

-Elevation is a movement that raises a bone vertically. Mandibles and clavicles are elevated

-Depression is lowering the mandible or the shoulders

-Protraction is movement anteriorly on horizontal plane (thrusting the jaw forward, shoulders or pelvis

forward)

-Retraction is movement posteriorly