classification of joints a joint (also called an articulation) is a point of contact between bones,...

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Classification of Joints

A joint (also called an articulation) is a point of contact between bones, between cartilage and bones, or between teeth and bone.

A joint’s structure determines its combination of strength and flexibility.


Classification of Joints Structural classification of joints is based on two

criteria:

1. Presence or absence of a space between the articulating

bones, called a synovial cavity, and

2. Type of connective tissue that holds the bones together.

Structurally, joints are classified as one of the following

types: Fibrous joints – no synovial cavity and bones are held

together by dense irregular connective tissue. Cartilaginous joints – no synovial cavity and the bones are

held together by cartilage. Synovial joints – united by the dense irregular connective

tissue of an articular capsule, and often by ligaments.


Classification of Joints

Functional classification of joints relates to the degree of movement they permit.

Functionally, joints are classified as one of the following types: Synarthrosis – An immovable joint.

Amphiarthrosis – A slightly movable joint.

Diarthrosis – A freely movable joint.


Fibrous Joints Fibrous joints permit little or no movement. The

three types of fibrous joints are (1) syndesmoses, (2) sutures, and (3) interosseous membranes

Syndesmosis – joint permits limited movement (distal tibia and fibula) and gomphosis (dentoalveolar joint)

Suture – fibrous joint that may be a slightly movable or immovable (found between skull bones) – need to know

Interosseous membranes – permits slight movement (between the radius and ulna and tibia and fibula)


Cartilaginous Joints Like a fibrous joint, a cartilaginous joint

allows little or no movement. Here the articulating bones are tightly

connected by either hyaline cartilage or fibrocartilage.

The two types of cartilaginous joints are: Synchondrosis – an immovable joint (epiphyseal

plate) Symphysis – a slightly movable joint (pubic

symphysis and intervertebral joints) – need to know


Synovial Joints The unique characteristic of a synovial joint is the presence

of a space called a synovial (joint) cavity between the

articulating bones. The synovial cavity allows a joint to be freely movable. The synovial membrane secretes synovial fluid, which

forms a thin, viscous film over the surfaces within the

articular capsule. Many synovial joints also contain accessory ligaments,

articular discs, fibrous & synovial membranes. Bursae are saclike structures, similar in structure to joint

capsules, that reduce friction in joints such as the shoulder

and knee joints.


Types of Movements at Synovial Joints Gliding is a simple movement, the nearly flat surfaces of

bones move back-and-forth and side-to-side. eg. Carpal bones

Angular movements, there is an increase or decrease in the

angle between bones (flexion–extension, hyperextension,

abduction–adduction, and circumduction). Eg. elbow

Rotation, is where a bone moves around its own longitudinal

axis. eg. atlas/axis

Special movements occur only at certain joints in the body.

Examples: elevation–depression, protraction–retraction,

inversion–eversion, dorsiflexion–plantar flexion,

supination–pronation, opposition. – need to know


Types of Synovial JointsSynovial joints are divided into 6 subtypes: plane,

hinge, pivot, condyloid, saddle, and ball-and-socket. In plane (planar) joints the articulating surfaces are

flat, and the bones glide back-and-forth and side-to-

side (many are biaxial); they may also permit rotation

(triaxial). Examples of plane joints are the joints

between carpals and the joints between tarsals. In hinge joints, the convex surface of one bone fits

into the concave surface of another, and the motion is

angular around one axis (uniaxial); examples are the

elbow, knee (a modified hinge joint), and ankle joints.


Types of Synovial Joints In pivot joints, a round or pointed surface of one bone fits

into a ring formed by another bone and a ligament, and

movement is rotational (uniaxial); examples are the atlanto-

axial and radioulnar joints. In condyloid joints, an oval projection of one bone fits into

an oval cavity of another, and motion is angular around two

axes (biaxial); examples include the wrist joint and

metacarpophalangeal joints of digits #2–5. In saddle joints, the articular surface of one bone is shaped

like a saddle and the other bone fits into the “saddle” like a

sitting rider; motion is angular around two axes (biaxial). An

example is the carpometacarpal joint between the trapezium

and the metacarpal of the thumb.


Types of Synovial Joints In ball-and-socket joints, the ball-shaped

surface of one bone fits into the cuplike depression of another; motion is around three axes (triaxial). Examples include the shoulder and hip joints.

The knee joint is the largest and most complex joint in the body. It contains an articular capsule, several ligaments within and around the outside of the joint, menisci, and bursae. Arthroplasty refers to the surgical replacement of severely damaged natural joints with artificial joints.


Aging and Joints Aging usually results in decreased

production of synovial fluid in joints. In addition, the articular cartilage becomes thinner with age, and ligaments shorten and lose some of their flexibility. The effects of aging on joints are influenced by genetic factors and by wear and tear and vary from one person to another.

Most individuals experience some degeneration in the knees, elbows, hips, and shoulders due to the aging process.

classification of joints a joint (also called an articulation) is a point of contact between bones,...

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