Articulations/Joints

Articulations/Joints

Topics Covered

Joints and their classification

Synarthrotic joints

Amphiarthrotic joints

Diarthrotic joints

Synovial joints anatomy

Types of synovial joints

Joints and Their Classification

*Joints can be classified by their freedom of movement*

 ·      Synarthrosis: little or no movement

o   Skull sutures, teeth in sockets, etc.

·      Amphiarthrosis: slightly movable

o   Intervertebral discs, pubic symphysis, etc.

·      Diarthrosis: freely movable

o   shoulder, elbow, carpal joints, knee, tarsal joints, etc.

*Or by their physical nature*

• Fibrous: collagen fibers spanning the space between bones
• Skull sutures, teeth in sockets, distal radioulnar joints, etc.
• Linked to figure on 9.5- fibrous joints

• Cartilaginous: 2 bones bound to each other by cartilage
• Intervertebral discs, pubic symphysis, etc.
• Linked to figure 9.7- cartilaginous joints

• Synovial: bones held together by joint capsule filled with synovial fluid
• Shoulder, elbow, carpal joints, knee, tarsal joints, etc.
• Linked to figure 9.8- synovial joints

**There is overlap between the 2 classification systems**

Synarthrotic Joints

·      No movement between bones

·      Types

o   Suture (linked to figure 9.5a)

§  Fibrous joint

§  Ex: adjacent bones in the cranium

o   Gomphosis

§  Fibrous joint

§  Ex: teeth in sockets of mandible or maxilla

o   Synchondrosis

§  Hyaline cartilaginous joint

§  Ex: joint between epiphyses and diaphyses of growing bones

o   Synostosisoccurs when two bones fuse and the joint becomes a bony joint

§  Ossification occurs with age between some cranial sutures and epiphyses and diaphyses of the long bones

Amphiarthrotic Joints

• Limited range of motion

• Types

·      Syndesmosis (most movable)

o   Fibrous joint – 2 bones bound by ligament only

o   Ex: Distal radius and ulna or distal tibia and fibula

·      Synchondrosis

o   Bones are bound by hyaline cartilage

o   Ex: Rib attachment to sternum by costal cartilage

·      Symphysis (least movable)

o   Bones are joined by fibrocartilage

o   Ex: Pubic symphysis

Diarthrotic Joints

·      All diarthrotic joints are synovial joints

·      Synovial joint: joint in which two bones are separated by a space called a joint cavity

·      Most are freely movable

Synovial joint anatomy (linked to figure 9.8-synovial joints)

·      fibrous capsule– outer part of synovial joint, is fused with ligaments

·       synovial membrane – inside the joint capsule; secretes synovial fluid

·       synovial fluid – lubricates the articular cartilage to reduce friction

·       synovial cavity – space inside the joint between the two articulating bones

·       articular cartilage – hyaline cartilage covering the ends of the bones in the synovial cavity

Types of synovial joints (linked to figure on 9.10- types of synovial joints)

1. Hinge

•       One bone with convex surface that fits

•       Into a concave depression on other bone

•       Change the angle between two bones

•       Angular movement

2.  Pivot

•       One bone has a projection that fits into a ringlike ligament of another

•       Allow for rotational movement between two bones

3.  Ball-and-socket

•       Smooth hemispherical head fits within a cuplike depression

•       Extensive movement, yet less stable (dislocation)

4.  Condyloid

•       A convex surface articulates with a concave surface

•       Allows significant movement in two planes

5.  Gliding

•       Allows movement between two plane surface

6.  Saddle

•       Two concave surfaces that articulate with one another

•       Similar, but, greater movement than a condyloid joint