The document discusses the classification and functional anatomy of joints in the human body. It describes three main classifications of joints: structural (fibrous, cartilaginous, synovial), functional (synarthrosis, amphiarthrosis, diarthrosis), and regional (skull, vertebral, limb type). It then focuses on the different types of synovial joints, providing examples of ball-and-socket, hinge, pivot, and other joints. It also outlines the blood supply, nerve innervation, development, and factors contributing to stability in synovial joints.

2. THE JOINTS
DR ABDUL SAMAD

3. OBJECTIVES
• INTRODUCTION
• STRUCTURAL CLASSIFICATION
• FUNCTIONAL CLASSIFICATION
• MOVEMENTS OF JOINTS
• BLOOD SUPPLY, NERVE SUPPLY AND
LYMPHATICS
• DEVELOPMENT OF JOINTS

4. INTRODUCTION
• A site where two or more bones come together,
whether or not movement occurs between them,
is called a joint.
• Joints permit movements.
• There are more joints in a child than in an adult
because as growth proceeds some of the bones
fuse together, e.g. the ilium, ischium and pubis to
form the pelvic bone; the two halves of the infant
frontal bone, and of the infant mandible; the five
sacral vertebrae and the four coccygeal
vertebrae.

5. CLASSIFICATION OF JOINTS
• A. Structural Classification.
• 1. Fibrous joints.
• (a) Sutures (b) Syndesmosis (c) Gomphosis.
• 2. Cartilaginous joints.
• (a) Primary cartilaginous joints or synchondrosis.
• (b) Secondary cartilaginous joints or symphysis.
• 3. Synovial joints.
• (a) Ball-and-socket or spheroidal joints (b) Sellar or saddle
joints (c) Condylar or bicondylar joints (d) Ellipsoid joints (e)
Hinge joints (f) Pivot or trochoid joints (g) Plane joints.

7. …cont.
• B. Functional Classification (according to the
degree of mobility).
• 1. Synarthrosis (immovable), like fibrous
joints.
• 2. Amphiarthrosis (slightly movable), like
cartilaginous joints.
• 3. Diarthrosis (freely movable), like synovial
joints.

8. …cont.
• C. Regional Classification:
• 1. Skull type: immovable.
• 2. Vertebral type: slightly movable.
• 3. Limb type: freely movable.
• D. According to number of articulating bones:
• 1. Simple joint: When two bones articulate.
• 2. Compound joint: More than two bones
articulate within one capsule
• 3. Complex joint: When joint cavity is divided by an
intra-articular disc.

9. • The structural classification is most common
and will be discussed in detail.

10. Fibrous Joints
• The articulating surfaces of the bones are joined by
fibrous tissue.
• These joints are either immovable or permit a slight
degree of movement.
• Types:
• 1. Sutures: These are peculiar to skull, and are
immovable.
• 2. Syndesmosis: The bones are connected by the
interosseous ligament. Example: inferior tibiofibular
joint.
• 3. Gomphosis (peg and socket joint). Example: root of
the tooth in its bony socket.

12. CARTILAGINOUS JOINTS
• In this type of joints the bones are joined by
cartilage. These are of the following two types:
• 1. Primary cartilaginous joints (synchondrosis, or
hyaline cartilage joints): is one in which the bones
are united by a plate or a bar of hyaline cartilage.
• Thus, the union between the epiphysis and the
diaphysis of a growing bone and that between the
1st rib and the manubrium sterni are examples of
such a joint.
• No movement is possible.

14. 2. Secondary cartilaginous joints
• 2. Secondary cartilaginous joints (symphysis or
fibro cartilaginous joints):is one in which the
bones are united by a plate of fibro cartilage
and the articular surfaces of the bones are
covered by a thin layer of hyaline cartilage.
• Examples are the joints between the vertebral
bodies and the symphysis pubis.
• A small amount of movement is possible.

15. Synovial Joints
• The articular surfaces of the bones are
covered by a thin layer of hyaline cartilage
separated by a joint cavity.
• This arrangement permits a great degree of
freedom of movement.
• It is the most mobile type of joints.

16. …cont.
• Characteristics of a synovial joint:
• The cavity of the joint is lined by synovial
membrane which extends from the margins of
one articular surface to those of the other.
• The synovial membrane is protected on the
outside by a tough fibrous membrane referred
to as the capsule of the joint.
• The articular surfaces are lubricated by a
viscous fluid called synovial fluid, which is
produced by the synovial membrane.

18. …cont.
• In certain synovial joints, for example, in the
knee joint, discs or wedges of fibro cartilage
are interposed between the articular surfaces
of the bones. These are referred to as articular
discs.
• Fatty pads are found in some synovial joints
lying between the synovial membrane and the
fibrous capsule or bone. Examples are found
in the hip and knee joints.

19. …cont.
• The degree of movement in a synovial joint is
limited by the shape of the bones
participating in the joint, thigh against the
anterior abdominal wall on flexing the hip
joint, and the presence of fibrous ligaments
uniting the bones.
• Most ligaments lie outside the joint capsule,
but in the knee some important ligaments, the
cruciate ligaments, lie within the capsule.

22. …cont.
• Synovial joints can be classified according to the
arrangement of the articular surfaces and the
types of movement that are possible.
• 1.Plane joints: In plane joints, the apposed
articular surfaces are flat or almost flat, this
permits the bones to slide or glide on one
another.
• Examples of these joints are the sternoclavicular
and acromioclavicular joints.

25. • 2.Hinge joints: Hinge joints resemble the
hinge on a door, so that flexion and extension
movements are possible.
• Examples of these joints are the elbow, knee,
and ankle joints.
• 3.Pivot joints: In pivot joints, a central bony
pivot is surrounded by a bony–ligamentous
ring.

28. …cont.
• Rotation is the only movement possible.
• The atlantoaxial and superior radioulnar joints are
good examples.
• 4.Condyloid joints: Condyloid joints have two
distinct convex surfaces that articulate with two
concave surfaces. The movements of flexion,
extension, abduction, and adduction are possible
together with a small amount of rotation. Examples:
• The metacarpophalangeal joints or knuckle joints
are good examples.

30. …cont.
• 5.Ellipsoid joints: In ellipsoid joints, an
elliptical convex articular surface fits into an
elliptical concave articular surface.
• .The movements of flexion, extension,
abduction, and adduction can take place, but
rotation is impossible.
• The wrist joint is a good example.

32. …cont.
• 6.Saddle joints: In saddle joints, the articular
surfaces are reciprocally concavo-convex and
resemble a saddle on a horse’s back.
• These joints permit flexion, extension,
abduction, adduction, and rotation.
• The best example of this type of joint is the
carpometacarpal joint of the thumb.

34. …cont.
• 7.Ball-and-socket joints: In ball-and-socket
joints, a ball shaped head of one bone fits into
a socket like concavity of another. This
arrangement permits free movements,
including flexion, extension, abduction,
adduction, medial rotation, lateral rotation,
and circumduction. The shoulder and hip
joints are good examples of this type of joint

36. BLOOD SUPPLY OF SYNOVIAL JOINTS
• The articular and epiphysial branches given off
by the neighboring arteries form a
periarticular arterial plexus. Numerous vessels
from this plexus pierce the fibrous capsule and
form a rich vascular plexus in the deeper parts
of synovial membrane.
• After epiphysial fusion, communications
between circulus vasculosus and the end
arteries of metaphysis are established, thus
minimizing the chances of osteomyelitis in the
metaphysis.

37. NERVE SUPPLY OF SYNOVIAL JOINTS
• The capsule and ligaments possess a rich
nerve supply.
• The synovial membrane has a poor nerve
supply and is relatively insensitive to pain.
• The articular cartilage is non-nervous and
totally insensitive.
• The principles of distribution of nerves to
joints were first described by Hilton:

38. …cont.
• Hilton's law states that a motor nerve to the
muscle acting on joint tends to give a branch
to that joint (capsule) and another branch to
the skin covering the joint.

40. Stability of Joints
• The stability of a joint depends on three main
factors:
• 1. The shape, size, and arrangement of the
articular surfaces.
• 2. The ligaments and
• 3. The tone of the muscles around the joint.

41. Muscle Tone
• is the continuous and passive partial contraction of
the muscles, or the muscle's resistance to passive
stretch during resting state.
• In most joints, muscle tone is the major factor
controlling stability.
• For example, the muscle tone of the short muscles
around the shoulder joint keeps the hemispherical
head of the humerus in the shallow glenoid cavity
of the scapula.

42. …cont.
• Without the action of these muscles, very
little force would be required to dislocate this
joint. The knee joint is very unstable without
the tonic activity of the quadriceps femoris
muscle. The joints between the small bones
forming the arches of the feet are largely
supported by the tone of the muscles of the
leg, whose tendons are inserted into the
bones of the feet.

43. 1.Articular Surfaces
• The ball-and-socket arrangement of the hip
joint and the mortise arrangement of the
ankle joint are good examples of how bone
shape plays an important role in joint stability.

44. 2.Ligaments
• Fibrous ligaments prevent excessive movement in a
joint, but if the stress is continued for an excessively
long period, then fibrous ligaments stretch. For
example, the ligaments of the joints between the
bones forming the arches of the feet will not by
themselves support the weight of the body. Should
the tone of the muscles that normally support the
arches become impaired by fatigue, then the
ligaments will stretch and the arches will collapse,
producing flat feet.

46. …cont.
• Elastic ligaments, conversely, return to their
original length after stretching. The elastic
ligaments of the auditory ossicles play an
active part in supporting the joints and
assisting in the return of the bones to their
original position after movement.