Joints and Articulations

Articulation

Site where two or more bones meet

Functions of joints

Mobility and holding skeleton together

Synarthroses

Immovable joints

Amphiarthroses

Slightly movable joints

Diarthroses

Freely movable joints

Fibrous Joints

Bones joined by dense fibrous connective tissue, mostly immovable

Cartilaginous Joints

Bones united by cartilage, no joint cavity

Synovial Joints

Joints separated by a fluid-filled cavity, all diarthrotic

Synovial fluid

Viscous filtrate of plasma lubricating and nourishing articular cartilage

Capsular ligaments

Thickened part of the fibrous capsule reinforcing synovial joints

Bursae

Flattened, fibrous sacs lined with synovial membranes acting as 'ball bearings'

Tendon sheath

Elongated bursa wrapping completely around a tendon

Muscle tone

Reinforces joints, especially shoulder, knee, and foot arches

Origin

Muscle attachment to the immovable bone

Insertion

Muscle attachment to the movable bone

Nonaxial

Slipping movements only

Uniaxial

Movement in one plane

Biaxial

Movement in two planes

Multiaxial

Movement in or around all three planes

Gliding

One flat bone surface sliding over another

Flexion

Decreases the angle of the joint

Extension

Increases the angle of the joint

Abduction

Movement away from the midline

Adduction

Movement toward the midline

Circumduction

Flexion + abduction + extension + adduction of a limb

Rotation

Turning of a bone around its own long axis

Saddle Joints

Biaxial joints allowing greater freedom of movement than condyloid joints

Ball and socket Joints

Multiaxial joints allowing the most freely moving synovial joints

Sutures

Joints between skull bones allowing for growth during youth

Syndesmoses

Bones connected by ligaments, with movement varying from immovable to movable

Gomphoses

Peg-in-socket joints of teeth in alveolar sockets

Synchondroses

Joints with a bar or plate of hyaline cartilage uniting the bones, all synarthrotic

Symphyses

Joints with hyaline cartilage covering articulating surfaces and fused to an intervening pad of fibrocartilage

6 features of synovial joints

1. articular cartilage

2. joint cavity

3. articular capsule

4. synovial fluid

5. reinforcing ligaments

6. nerves and blood vessels

Synovial fluid

Viscous slippery filtrate of plasma from capillaries in the synovial membrane + hyaluronic acid; lubricates and nourishes articular cartilage

Reinforcing ligaments

Three possible types: capsular (intrinsic), extracapsular, and intracapsular

Rich nerve and blood vessel supply

Nerve fibers detect pain, monitor joint position and stretch; capillary beds produce filtrate for synovial fluid

Articular capsule

-Outer fibrous capsule of dense irregular connective tissue that is continuous with the periostea of the articulating bones

-Inner synovial membrane of loose connective tissue

Common Joint Injuries luxations and subluxations

Dislocations (luxations)

Bones forced out of alignment

Accompanied by sprains, inflammation, and difficulty moving joint

Caused by serious falls or contact sports

Subluxation

partial dislocation of a joint

Osteoarthritis (OA)

Common, irreversible, degenerative ("wear-and-tear") arthritis

Rheumatoid Arthritis

Chronic, inflammatory, autoimmune disease of unknown cause

GoutyArthritis

Deposition of uric acid crystals in joints and soft tissues, followed by inflammation

Lyme Disease

•Caused by bacteria transmitted by the bites of ticks

Bursitis

An inflammation of a bursa, usually caused by a blow or friction

Tendonitis

Inflammation of tendon sheaths typically caused by overuse