The principles of articulation: fibrous, cartilaginous and synovial joints

Question 1

Structural classification of joints

Answer 1

Presence of absence of a synovial cavity and the type of connective tissue

Described as either fibrous, cartilaginous or synovial

Question 2

Functional classification of joints

Answer 2

Based on the degree of movement permitted

• synarthrosis (immovable)
• amphiarthrosis (partially moveable)
• diarthrosis (freely moveable)

Question 3

Fibrous joints

Answer 3

No synovial cavity

Held together by a fibrous connective tissue

Permits little or no movement (synarthrosis/ amphiarthrosis)

Question 4

Three types of fibrous joint

Answer 4

Suture

Syndesmosis

Interosseous membrane

Question 5

Fibrous joints- suture

Answer 5

Unite skull bones

Thin layer of dense connective tissue

Irregular

Interlocking edges provide strength, permit no movement (synarthrosis)

Ossification of a suture forms a synostosis

Question 6

Fibrous joints- syndesmosis

Answer 6

More connective tissue than seen in a suture

Crosses a greater distance than a suture

Connective tissue typically arranged into bundles (ligament)

Typically permit slight movement (amphiarthrosis)

Question 7

Fibrous joints- interosseous membranes

Answer 7

Sheet of dense connective tissue

Binds adjacent long bones

Amphiarthrosis

Two main examples between the radius and ulna in forearm, and tibia and fibula in the leg

Question 8

Cartilaginous joints

Answer 8

No synovial cavity

Held together by a fibrocartilage or hyaline cartilage

Permits little or no movement (synarthrosis/ amphiarthrosis)

Question 9

Two types of cartilaginous joint

Answer 9

Synchrondosis

Symphysis

Question 10

Cartilaginous joints- synchrondosis

Answer 10

The connective tissue is hyaline cartilage

Synarthrosis

e.g. epiphyseal plate

At skeletal maturity the epiphysis, metaphysis and epiphyseal plate fuse forming a synostosis

Question 11

Cartilaginous joints- symphysis

Answer 11

Connective tissue is fibrocartilage

Adjacent bones lined with hyaline cartilage, but with a broad disc of fibrocartilage connects the bones

Amphiarthrosis

All symphysis occur in the midline of the body

• junction of the manubrium and sternum
• intervertebral discs
• pubic symphysis

Question 12

Synovial joints

Answer 12

Synovial cavity between articulating bones

Freely moveable- diarthrosis

Layer of hyaline cartilage called articular cartilage

Question 13

Synovial joint structure articular cartilage

Answer 13

Covers the bones at synovial joints

Avascular

Composed of collagen and proteoglycan

Orientation of collagen structure imparts resistance to compression and an extremely low resistance surface

Question 14

Synovial joint structure avascular capsule

Answer 14

Encapsulates a synovial joint

Composed of two layers

Outer fibrous membrane connects to periosteum

• flexibility permits movement
• fibres arranged into bundles, high tensile strength

Inner layer termed synovial membrane

• areolar connective tissue rich in elastic fibres
• occasionally contains structural articular fat pads

Question 15

Synovial joint structure synovial fluid

Answer 15

Secreted by synovial membrane

Rich in hyaluronic acid, secreted by fibroblast like cells, and interstitial fluid from blood plasma

Lubricates articular surface- reducing friction

Provides some shock absorbing properties

Supplies nutrition to, and removes waste products from the avascular articular cartilage

Phagocytes remove microbes and debris

Question 16

Synovial joint structure accessory ligaments

Answer 16

Intracapsular ligaments lie within the joint capsule

• excluded form synovial fluid by folds in synovial membrane
• e.g. anterior and posterior cruciate ligaments of the knee

Extracapsular ligaments lie outside the joint capsule
- e.g. fibular and tibial collateral ligaments of the knee

Question 17

Synovial joint structure accessory articular discs

Answer 17

Fibrocartilage pads lie between articular cartilage of some synovial joints e.g. meniscus of the knee

Called meniscii or articular discs

Help maintain joint stability

Direct the flow of synovial fluid

Meniscal tears (common in athletes)

Question 18

Synovial joint structure nerve and blood supply

Answer 18

Nerve endings same as those that supply associated muscles

Distributed to the articular capsule and associated ligaments

Pain and proprioception

Many components of the synovial joint are avascular

Rely on numerous branching of arteries and veins to supply associated tissue

Question 19

Synovial joint structure bursae and tendon sheaths

Answer 19

Moving parts of joints can cause friction

Bursae are fluid filled sacs lined with synovial like membrane

Bursae cushion movement between body parts

Tendon sheaths are similar to bursae

Specialised membranes that wrap around tendons

Especially where many tendons come together and/ or pass through a synovial joint capsule

Question 20

Types of synovial joints- movement

Answer 20

Planar

Hinge

Pivot

Condyloid

Saddle

Ball and socket

Question 21

Types of synovial joints- planar

Answer 21

Surfaces flat or slightly curved

Permit back and forth, and side to side movements

Examples include:

• intercarpal joints (between carpal bones at the wrist)
• intertarsal joints (between tarsal bones at the ankle)

Question 22

Types of synovial joints- hinge

Answer 22

Concave surface of one bone fits the convex surface of another

Permits motion in a single axis (flexion and extension)

Examples include

• knee joints
• elbow joints

Question 23

Synovial joints- pivot

Answer 23

Rounded or pointed surface of one bone pivots inside a ring formed by the other bone and a ligament

Permits rotation in its longitudinal axis (monoaxial)

Examples include

• radioulnar joints
• atlanto-axial joint

Question 24

Types of synovial joints- condyloid

Answer 24

Convex oval projection of one bone fit into the oval depression of the other

Permits movement around two axis (biaxial, flexion and extension, and abduction and adduction)

Examples include

• wrist joint
• metacarpophalangeal joints

Question 25

Types of synovial joints- saddle

Answer 25

One bone fits into the saddle shaped bone it opposes

Modified condyloid joint

Permits movement around two axis (biaxial, flexion and extension, abduction and adduction (sometimes limited rotation)

Examples include
- carpometacarpal joint

Question 26

Types of synovial joints- ball and socket

Answer 26

Ball like surface of one bone fits into the cup-like depression of the other

Triaxial movement around three planes (triaxial, flexion and extension, abduction and adduction, and rotation)

Examples include

• shoulder joint
• hip joint

Question 27

Glenohumeral (shoulder) joint

Answer 27

Synovial ball and socket joint

Joint between the proximal humerus and the scapula (glenoid fossa)

Due to the shallowness of the glenoid cavity, it is the most mobile joint in the body

GLenoid labrum: a narrow rim of fibrocartilage- deepens glenoid

Stabilised by three ligaments

• glenohumeral
• coracohumeral
• transverse humeral

Four associated bursae

Question 28

Glenohumeral joint- rotator cuff muscles

Answer 28

Most strength from rotator cuff muscles

• supraspinatus
• infraspinatus
• teres minor
• subscapularis

Join the scapula with the humerus

Encircle the joint and fuse with joint capsule

Question 29

Acromioclavicular joint

Answer 29

Technically a synovial gliding joint (planar) but it acts like a pivot

Joint between the acromion and the clavicle

Stablised by three ligaments

• acromioclavicular
• coracoacromial
• coracoclavicular (conoid and trapezoid)

Allows the movement of the scapula, permitting greater arm rotation (above the head)

Question 30

Sternoclavicular joint

Answer 30

Synovial saddle joint

Medial clavicle fits into a hollow formed by the superlateral surface of the manubrium and the medial costal cartilage of the first rib

Fibrocartilagenous articular disc divides the joint into two synovial cavities

Reinforced by interclavicular, anterior and posterior sternoclavicular ligaments