Ch. 8 Joints of the Skeletal System

Part 1:Classifying Joints& Joint Movements

Interactive pages 269-278

Types of Joints(AKA: Articulations)

● Structural Classification (type of

tissue that binds the bones

○ Fibrous

○ Cartilaginous

○ Synovial

● Functional Classification (degree

of movement)

○ Synarthrotic

■ Immovable

○ Amphiarthrotic

■ Slightly Moveable

○ Diarthrotic

■ Freely Moveable

Fibrous Joints

● Bones bound by dense connective tissue (collagen fibers)

● Types of Fibrous Joints

○ Syndesmosis

■ Bound by a sheet (interosseous membrane) or bundle (interosseous ligament)

of Dense C.T.

■ Permits slight movement (amphiarthrosis) such as twisting between the tibia

and the fibula

○ Sutures

■ Between plates of the skull (fontanels in infancy)

■ Immovable (synarthrotic)

○ Gomphosis

■ Union of a bony process in a socket (root of tooth attached to mandible or

maxilla by periodontal ligament)

■ Immovable

Syndesmosis SutureGomphosis

Cartilaginous Joints

● Bones bound by cartilage or fibrocartilage

● Types of Cartilaginous Joints

○ Synchondrosis

■ Hyaline Cartilage

■ Most Temporary during growth (ex. Epiphyseal plate)

■ Becomes synostosis at maturation

■ Permanent Synchondrosis between manubrium & 1st rib (sternocostal joint)

○ Symphysis

■ Articulating bones covered in hyaline cartilage

■ Connected by a pad of fibrocartilage

■ Ex. Pubic symphysis & intervertebral joints

Synchondrosis Symphysis

Synovial Joints: General Structure

● Freely Moveable (Diarthrosis)

● Ends of bones covered in hyaline cartilage called Articular Cartilage

● Bones held together by joint capsule

○ Outer layer is Dense C.T. fibers attach to periosteum

○ Inner layer is Loose C.T.

■ Synovial membrane

■ Secretes synovial fluid

● Synovial fluid testing may indicate arthritis, gout, or infection

● Ligaments reinforce the joint capsule

● Accessory Structures of the Joint

○ Menisci

■ Pad of fibrocartilage that cushion and distribute weight

○ Bursae

■ Fluid filled sacs that cushion tendons that glide over bones

Synovial Joint

StructureAccessory Structures

Synovial Joints: Types

● Ball & Socket or Spheroidal

○ Wide range of motion (multiaxial movement)

○ Rounded head articulates with cup-shaped cavity of another bone

○ Hip (Acetabulofemoral) & Shoulder (Glenohumeral)

● Condylar or Ellipsoidal

○ Back and forth/Side to Side (biaxial movement)

○ Oval condyle of one bone fits into the elliptical cavity of another

○ Metacarpophalangeal joints

● Plane or Gliding

○ Sliding and Twisting (nonaxial movement)

○ Flat articulating surfaces

○ Intercarpal & Intertarsal joints

Synovial Joints: Types

● Hinge

○ One plane of movement (uniaxial)

○ Convex/Concave articulating surfaces

○ Humeroulnar joint and interphalangeal joints

● Pivot or Trochoid

○ Rotation in one plane (uniaxial)

○ Cylindrical surface of one bone rotates in a ring of bone and ligament

○ Atlantoaxial joint & proximal radioulnar joing

● Saddle or Sellar

○ Wide range of motion (biaxial)

○ Both bones have a convex and concave surface

○ Carpometacarpal 1

Types of Joint Movements

● Flexion: ○ Bending at joint to decrease angle

● Extension○ Moving at a joint to increase angle

● Hyperextension○ Extension beyond anatomical

position

● Abduction○ Moving part away from midline

● Adduction○ Moving part towards midline

Types of Joint Movements● Dorsiflexion

○ Movement at ankle that moves anterior

foot closer to the shin

● Plantar flexion○ Movement at the ankle that moves

anterior foot farther from shin

● Medial rotation○ Turning limb toward midline

● Lateral rotation○ Turning limb away from midline

● Pronation○ Rotate forearm to palm down

● Supination○ Rotate forearm to palm up

● Circumduction○ Moving a part so that the end follows a

circular path

Types of Joint Movements● Inversion

○ Turning plantar surface medially

● Eversion○ Turning plantar surface laterally

● Protraction○ Moving a part forward

● Retraction○ Moving a part backward

● Elevation○ Raising a part

● Depression○ Lowering a part

Part 2:Specific Synovial Joints & Disorders

Interactive pages 277-288

Examples of Synovial JointsExamples of large, complex synovial (also freely movable) joints:

• Shoulder.

• Elbow.

• Hip.

• Knee.

Figure 8.13a Shoulder Joint

Shoulder Joint:

AKA Glenohumeral Joint

• Ball-and-socket.

• Head of humerus and glenoid cavity of scapula.

• Loose joint capsule.

• Ligaments prevent displacement.

• Glenoid labrum.

• Several bursae.

• Very wide range of movement, including rotation, circumduction.

Major ligaments of the shoulder joint:

• Coracohumeral ligament.

• Glenohumeral ligaments.

• Transverse humeral ligament.

Left: © Dr. Ronald Bergman

Elbow Joint:

Contains 2 articulations:

Humeroulnar & Humeroradial

Hinge joint:

• Between trochlea of humerus and trochlear notch of ulna.

• Flexion / extension only.

Plane (gliding) joint:

• Between capitulum of humerus and fovea on head of radius.

• Pronation / supination.

• Several reinforcing ligaments.

Major ligaments of elbow joint:

• Radial collateral ligament.

• Ulnar collateral ligament.

• Anular ligament.

Hip Joint:

AKA: Acetabulofemoral

• Ball-and-socket joint.

• Head of femur and acetabulum of hip bone.

• Acetabular labrum.

• Heavy joint capsule.

• Many reinforcing ligaments.

• Variety of movement, yet less than at shoulder joint.

Major ligaments of the hip joint:

• Iliofemoral ligament (strongest ligament in body).

• Pubofemoral ligament.

• Ischiofemoral ligament.

Left: © Dr. Ronald Bergman

Clinical Application 8.1

● Synthetic materials are used to replace joints damaged by arthritis or injury.

● Steel and titanium replace larger joints, silicone used for smaller joints, some are ceramic.

● Hip replacements are the most common.

● New technology for joint replacement:

• Use of materials that resemble natural body chemicals, such as coating implant with hydroxyapatite.

• 3D printing technology used to create custom replacement joints.

Knee Joint:

AKA: Tibiofemoral

Largest & most complex joint.

3 bones:

• Femur: Medial and lateral condyles of distal end.

• Tibia: Medial and lateral condyles of proximal end.

• Patella: Articulates with anterior surface of femur.

Strengthened by many ligaments.

and tendons.

Cushioned by bursae, fat pads.

Menisci separate femur and tibia.

Major ligaments of the

knee joint:

• Patellar ligament.

• Oblique popliteal

ligament.

• Arcuate popliteal

ligament.

• Tibial (medial) collateral

ligament.

• Fibular (lateral) collateral

ligament.

• Anterior cruciate

ligament.

• Posterior cruciate

ligament.

Knee joint characteristics:

• Modified hinge joint between condyles.

• Flexion / extension.

• Some rotation when knee is flexed.

• Plane joint between femur & patella.

Joint Disorders

Sprains: Tearing of connective tissue in joint, without bone dislocation.

Bursitis: Inflammation of a bursa, from overuse or stress.

Arthritis: Inflammation, swelling, and pain in a joint.

• Rheumatoid arthritis: autoimmune disease.

• Osteoarthritis: degenerative, most common type, occurs with aging.

• Lyme arthritis: caused by Lyme disease, passed through tick bite.

Lifespan Changes

• Joint stiffness is an early sign of aging.

• Many people develop arthritis as they age.

• Fibrous joints first to change; can strengthen, however, over a lifetime

• Cartilage in synchondroses stiffens.

• Ligaments lose elasticity.

• Changes in symphysis joints of vertebral column diminish flexibility and decrease height (due to water loss from the intervertebral discs).

• Synovial joints lose function, as capillary supply diminishes.

• Disuse hampers the nutrient supply to joints; speeds up stiffening.

• Activity and exercise can keep joints functional longer.