JOINTS – SYNDESMOLOGY

Question 1

TYPES OF ARTICULATIONS

There are three major classifications of joints based on the type of tissue that binds the bones together.

Answer 1

Fibrous joints
Cartilaginous joints
Synovial joints

Question 2

TYPES OF ARTICULATIONS

Fibrous joints

Answer 2

These are fixed or non-movable joints. There is no synovial cavity and the bones are held together by fibrous connective tissue that contains many collagen fibres.

• Sutures of the skull
• Interosseous membrane – between lower end of tibia and fibula, also radius and ulna

Question 3

TYPES OF ARTICULATIONS

Cartilaginous joints

Answer 3

These are slightly movable joints. There is no synovial cavity and bones are held together by either hyaline cartilage or fibro cartilage.

• Ribs to sternum (hyaline cartilage)
• The adjacent vertebrae, the two pubic bones of the pelvis (fibro cartilage)
• Epiphyseal plate

Question 4

TYPES OF ARTICULATIONS

Synovial joints

Answer 4

This is the most common type of joint in the body and is freely movable. There is a synovial cavity united by a surrounding articular capsule.

• Shoulder
• Hip

Question 5

STRUCTURE OF A SYNOVIAL JOINT

Joint surfaces

Answer 5

Joint surfaces are shaped to accept each other. The surfaces of the joint are covered with hyaline. The hyaline cap has three functions:
• Protects the bone from compression and shearing forces
• Provides a smooth friction-free surface
• Hard wearing adding resiliency to the joint

Question 6

STRUCTURE OF A SYNOVIAL JOINT

Joint capsule

Answer 6

The epiphyses of the adjacent bones are held together by the joint capsule that is composed of white fibrous tissue. The edges of this fibrous cuff merge with the periosteum of the bones involved, and the whole structure is strong and stretch resistant. Therefore, the capsule plays an important part in maintaining joint stability.

Question 7

STRUCTURE OF A SYNOVIAL JOINT

Synovial membrane

Answer 7

Lining the inside of the capsule is the synovial membrane – it has an abundant nerve and blood supply. It also has a profusion of specialised cells that secrete synovial fluid (an egg-white like fluid) into the joint. Normally there is only a small amount of synovial fluid present. It will increase with exercise as well as when the joint is damaged.
The synovial fluid acts as a lubricant to the articular surfaces and nourishes them.

Question 8

STRUCTURE OF A SYNOVIAL JOINT

Ligaments

Answer 8

Ligaments join bones together. They are strong bands of white fibrous tissue that run between the ends of the bones forming the joint.

Ligaments can exist as well-defined thickenings in the joint capsule or as completely independent structures outside or inside the capsule. They
• serve a protective function
• hold the articular surfaces together
• prevent excessive joint movement

Question 9

CARTILAGINOUS STRUCTURES WITHIN THE JOINT

Answer 9

The functions of cartilaginous structures are:
• To improve joint stability
• To reduce pressure and friction on the articular surfaces
• In some instances, to absorb shock (semi-lunar cartilages in knee joint, glenoid labrum in the shoulder joint)

Question 10

BURSAE

Answer 10

A bursa is a small flat sac made of white fibrous tissue and lined with synovial membrane. As in the synovial joint, the synovial membrane secretes fluid into the potential space within the bursa. These sacs are interposed between structures where eroding friction might occur.

Question 11

FAT PADS

Answer 11

Movements of joint surfaces will cause changes in size and shape of the intracapsular space. Small pads of fat often exist around the margins of joints that can move to accommodate the changing spaces within the joint. Although these are firmly anchored, they can sometimes become nipped and inflamed.

Question 12

TYPES OF SYNOVIAL JOINTS

Six

Answer 12

Ball and socket joints
Hinge joints  
Pivot joints  
Condyloid joints
Planar or gliding joints  
Saddle joints

Question 13

Ball and socket joints

Answer 13

Capable of all movements – flexion, extension, abduction, adduction, circumduction and rotation.

• Shoulder and hip joints

Question 14

Hinge joints

Answer 14

They permit movement in one plane only – flexion and extension.

• Fingers and elbows

Question 15

Pivot joints

Answer 15

Movement is limited to rotation. The joint is formed by either a pivot turning within a ring
• Proximal radio/ulna joint
or a ring turning on a pivot
• Atlas/axis
The ring is formed partly by bone and partly by ligament.

Question 16

Condyloid joints

Answer 16

An oval-shaped projection of one bone fits into an oval cavity of another.

• Wrist joints

Question 17

Planar or gliding joints

Answer 17

The articulating surfaces are flat. The gliding movements are restricted by ligaments of osseous processes around the articulation.

• Between the articular processes of the vertebrae
• Between many of the carpal and tarsal joints

Question 18

Saddle joints

Answer 18

The articular surface of one bone is shaped like a saddle and the other bone fits into the ‘saddle’ like a rider on a horse.

• Carpometacarpal joint between trapezium and metacarpal of the thumb