Bones and Joints

Question 1

What is a joint?

Answer 1

A joint or articulation or arthrosis is a point of contact between neighbouring bones, between cartilage and bones, or between teeth and bones. The structural
characteristics of a specific joint affect the strength, magnitude of movement, and types of movement that may occur at a specific joint.

Question 2

How do we classify joints?

Answer 2

Based on the presence or absence of a synovial cavity and the type of connective tissue that binds the bones together, the structural classification of joints categorizes joints into three major types:

• fibrous joints
•  cartilaginous joints
•  synovial joints

Question 3

What are fibrous joints?

Answer 3

Fibrous joints lack a synovial cavity and the articulating bones are held very closely together by fibrous connective tissue; they permit little or no movement.

Question 4

What are cartilaginous joints?

Answer 4

Cartilaginous joints lack a synovial cavity, and the articulating bones are tightly connected by cartilage; they permit little or no movement. Primary or secondary.

Question 5

What are primary cartilaginous joints?

Answer 5

The connecting tissue is hyaline cartilage  an example is an epiphyseal plate

Question 6

What are secondary cartilaginous joints?

Answer 6

Secondary cartilaginous joints (symphyses) - the connecting tissue is a disc of fibrocartilage  an example is the pubic symphysis

Question 7

What are synovial joints?

Answer 7

Synovial joints are characterized by the presence of a synovial (joint) cavity.
Additional important characteristics include:
- articular cartilage
- articular capsule composed of two layer (outer fibrous capsule that may have ligaments and an inner synovial membrane which secretes the lubricating synovial fluidthat fills the synovial cavity)

Many synovial joints also contain:

•  accessory ligaments, including extracapsular ligaments and intracapsular ligaments
•  articular discs or menisci
•  rich blood and nerve supply
• fluid-filled sacs called bursae
• tube-like bursae called tendon sheaths reduce friction at some joints during movements.

Question 8

What are the different types of synovial joint?

Answer 8

• Planar
• Hinge
• Pivot
• Ellipsoidal
• Saddle
• Ball and socket

Question 9

What are planar joints?

Answer 9

• Joint at which gliding movements may occur
• Articulating surfaces are usually flat or slightly curved, only side-to-side and back-and-forth movements are permitted without movement around any axis; it is a nonaxial joint an example is the sternoclavicular joint

Question 10

What are hinge joints?

Answer 10

Monaxial or uniaxial joint at which the convex surface of one bone fits into the concave surface of another bone flexion and extension (and sometimes hyperextension) may occur examples include the knee joint, elbow joint, and ankle joint

Question 11

What are pivot joints?

Answer 11

Monaxial joint at which rounded or pointed surface of one bone articulates within a ring formed partly by another bone and partly by a ligament. Rotation may occur. An example is rotation of the atlas around the dens of the axis when turning the head

Question 12

What are ellipsoidal joints?

Answer 12

Biaxial joint at which the oval-shaped condyle of one bone rests against the elliptical cavity of another bone.
The four angular movements (and circumduction) may occur. An example is the wrist joint.

Question 13

What is a saddle joint?

Answer 13

Biaxial joint at which articular surface of one bone is saddle-shaped and the articular surface of the other bone resembles the legs of a rider sitting in a saddle. It is technically a modified ellipsoidal joint in which movement is less restricted. An example is the joint between the trapezium and the base of the first metacarpal.

Question 14

What is a ball and socket joint?

Answer 14

Multiaxial (or polyaxial) joint at which the ball-like surface of one bone rests against the cup- like depression of another bone  the four angular movements and rotation may occur. The only examples are the shoulder and hip joints

Question 15

What are the types of movements at synovial joints?

Answer 15

• Gliding
• Angular movements
• Rotation
• Special movements

Question 16

What are gliding movements?

Answer 16

Articulating surfaces slide across each other

Question 17

What are angular movements?

Answer 17

Change in the angle between articulating bones. Examples include flexion, extension, abduction, adduction, and circumduction (a movement in which the distal end of a bone moves in a circle while the proximal end remains stable; it is typically a combination of the four angular movements and rotation).

Question 18

What are rotatory movements?

Answer 18

Rotation in which a bone turns around its own longitudinal axis. There are two types: medial (or internal) rotation and lateral (or external) rotation.

Question 19

What are elevation and depression ?

Answer 19

Elevation and depression are, respectively, an upward movement of a part of the body (e.g., elevating the mandible to close the mouth), and a downward movement of a part of the body (e.g., depressing the mandible to open the mouth)

Question 20

What are protraction and retraction?

Answer 20

Protraction and retraction are movements of the mandible or shoulder girdle forward or backward, respectively, on a plane parallel to the ground

Question 21

What are inversion and eversion?

Answer 21

Inversion and eversion are movements of the sole of the foot medially or laterally, respectively. These facilitate walking on uneven surfaces.

Question 22

What are dorsiflexion and plantar flexion?

Answer 22

Dorsiflexion and plantar flexion are bending of the ankle joint so that the foot moves in a dorsal or plantar (sole) direction, respectively


Question 23

What are supination and pronation?

Answer 23

Supination and pronation are movements of the forearm in which the palm turns anteriorly/superiorly or posteriorly/inferiorly, respectively

Question 24

What is opposition?

Answer 24

Opposition is the movement of a thumb across the palm to touch the fingertips on the same hand.

Question 25

What are the factors affecting contact and range of motion at synovial joints?

Answer 25

• Structure or shape of the articulating bones
• Strength and tension (tautness) of the joint ligaments  – Arrangement and tone of muscles around the joint
• Apposition of neighbouring soft tissues
• Effect of hormones (e.g., relaxin relaxes pelvic joints toward the end of pregnancy)
• Disuse of a joint

Question 26

Describe the effects of ageing on joints?

Answer 26

The effects of ageing on joints are variable among individuals and are affected by genetic factors and wear and tear; the ageing process usually results in:

•  decreased production of synovial fluid
•  thinning of articular cartilage
•  shortening of ligaments
• decrease in ligamentous flexibility
•  degenerative changes in load-bearing joints

Question 27

What is arthritis?

Answer 27

Arthritis is characterised by inflammation and stiffness of a joint. There are more than 100 different forms of arthritis. However, they have in common the symptoms of pain, swelling and stiffness and the signs of erythema (redness) overlying the affected joint, swelling deformity, tenderness, and reduced range of movement. When walking, this commonly manifests in an abnormal gait.

Question 28

What is osteoarthritis ?

Answer 28

Osteoarthritis. This is ‘wear and tear’ arthritis and is the most common form of arthritis. In osteoarthritis we see wearing away of the articular surfaces with consequent loss of joint space and ultimately bone grinding on bone, generating severe pain and loss of range of movement.

Question 29

What are the X-ray features of osteoarthritis?

Answer 29

The X-ray features of osteoarthritis are:

•  joint space narrowing
•  subchondral sclerosis (a thin layer of increased bone density beneath the articular cartilage)
•  osteophytes (bony spurs due to new bone formation at the margins of arthritic joints)
•  subchondral cysts (fluid filled sacs in the bone beneath the articulating cartilage).

Question 30

What is rheumatoid arthritis?

Answer 30

Rheumatoid arthritis, in contrast, is an autoimmune disease in which autoantibodies, known as rheumatoid factor, attack the synovial membrane. This leads to joint erosion and deformity particularly affecting the MCPJ and PIPJ of the hands, the feet and the cervical spine. It can also involve the large joints. The autoimmune process also leads to damage to other organs, including the eyes, skin, lungs, heart and blood vessels and the kidneys. Patients with rheumatoid arthritis also commonly have anaemia of chronic disease.

Question 31

Give an example of a fibrous joint

Answer 31

Examples of fibrous joints include the sutures of the skull, the inferior tibiofibular joint, the radioulnar interosseous membrane, the posterior sacroiliac joint and the joints that occur between the roots of the teeth and the bone of mandible or maxilla.

Question 32

What are the functions of bones?

Answer 32

• Support
• Protection
• Movement
• Mineral and growth factor storage
• Haematopoeisis