Chapter 7 joints

Chapter 7:
Joints
© 2013 John Wiley & Sons, Inc. All rights reserved.

Joints
 Classification of joints
 Fibrous joints
 Cartilaginous joints
 Synovial joints
 Types of movements at synovial joints
 Types of synovial joints
 Aging and joints

Classification of Joints
 A joint (articulation) is a point of contact between two bones,
cartilage and bone, or teeth and bone.
 A joint’s structure determines its combination of strength and
flexibility.
 Structural classification is based on the presence or absence of a
synovial cavity and the type of connecting tissue. Structurally, joints
are classified as fibrous, cartilaginous, or synovial.
 Functional classification of joints is based on the degree of
movement permitted. A joint may be a synarthrosis (immovable),
amphiarthrosis (slightly movable), or diarthrosis (freely movable).

 The structural classification of joints is based on two criteria: (1) the
presence or absence of a space between the articulating bones,
called a synovial cavity, and (2) the type of connective tissue that
holds the bones together. Structurally, joints are classified as one of
the following types:
 Fibrous joints (FĪ-brus). There is no synovial cavity and the
bones are held together by dense irregular connective tissue that
is rich in collagen fibers.
 Cartilaginous joints (kar-ti-LAJ-i-nus). There is no synovial
cavity and the bones are held together by cartilage.
 Synovial joints (si-NŌ-vē-al). The bones forming the joint have a
synovial cavity and are united by the dense irregular connective
tissue of an articular capsule, and often by accessory ligaments.

 The functional classification of joints relates to the degree of
movement they permit. Functionally, joints are classified as one of
the following types:
 Synarthrosis (sin-ar-THRŌ -sis; syn- = together). An immovable
joint. The plural is synarthroses.
 Amphiarthrosis (am-fē-ar-THRŌ-sis; amphi- = on both sides). A
slightly movable joint. The plural is amphiarthroses.
 Diarthrosis (dī-ar-THRŌ-sis = movable joint). A freely movable
joint. The plural is diarthroses. All diarthroses are synovial joints.
They have a variety of shapes and permit several different types
of movements.

Anatomy Overview:
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• Joints

Fibrous Joints
 In fibrous joints there is no joint cavity and the bones are
held together by dense irregular connective tissue.
 A fibrous joint may be a slightly movable or immovable suture
(found between skull bones), a slightly movable
syndesmosis (such as the distal joint between the tibia and
fibula), an immovable gomphosis (such as the root of a tooth
in an alveolus of the mandible and maxilla), or a slightly
movable interosseous membrane (found between the radius
and ulna and tibia and fibula).

Fibrous Joints

Cartilaginous Joints
 There is no joint cavity and the bones are held
together by cartilage in cartilaginous joints.
 These joints can be an immovable synchondrosis
united by hyaline cartilage (epiphyseal plates) or a
slightly movable symphysis united by fibrocartilage
(pubic symphysis).

Cartilaginous
Joints

Synovial Joints
 A synovial joint contains a synovial (joint) cavity. All synovial joints are
diarthroses.
 Other characteristics of a synovial joint are the presence of articular
cartilage and an articular ( joint) capsule, made up of a fibrous
membrane and a synovial membrane.
 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 and articular
discs.
 Bursae are saclike structures, similar in structure to joint capsules, that
reduce friction in joints such as the shoulder and knee joints.

Synovial Joints

Types of Movements at Synovial Joints
 In a gliding movement, the nearly flat surfaces of bones move back-and-
forth and side-to-side.
 In angular movements, there is a change in the angle between bones.
Examples are flexion–extension, hyperextension, abduction–
adduction, and circumduction.
 In rotation, a bone moves around its own longitudinal axis.
 Special movements occur at specific synovial joints in the body. Examples
are as follows: elevation–depression, protraction–retraction, inversion–
eversion, dorsiflexion–plantar flexion, and supination–pronation.

Types of Movements at Synovial Joints

Anatomy Overview:
You must be connected to the internet to run this animation.
• Selected Muscles and Movements

Types of Synovial Joints
 Types of synovial joints are 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.
 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 the second through fifth digits.
 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.
 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 a diarthrosis that illustrates the complexity of this type of joint
(Exhibit 7.A). 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
 With aging, a decrease in synovial fluid, thinning
of articular cartilage, and decreased flexibility of
ligaments occur.
 Most individuals experience some degeneration
in the knees, elbows, hips, and shoulders due to
the aging process.

Aging and Joints

End of Chapter 7
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Chapter 7 joints

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