(articulations): sites where 2 or more bones make contact.

·      weakest parts of the skeleton

·      functions: holds skeleton together and allows mobility

3 types of joints

(structures)

o   Fibrous joint: bones held together by dense fibrous connective tissue

o   cartilaginous joint: bones held together by cartilage (fibrocartilage or hyaline)

o   Synovial joint: bones held together by fluid-filled joint cavity (majority of joints)

   o   synarthroses: immovable

o   amphiarthroses: slightly movable. (amphi prefix means double)

o   diarthroses: freely movable.

*In general:

o   Fibrous joints are synarthrotic

o   cartilaginous joints can be either synarthrotic or amphiarthrotic

o   synovial joints are diarthrotic.

1.    Sutures: interlocking bone edges connected by very short collagen fibers; found only in the skull.

2.    Syndesmoses: bones connected by long collagen fibers (ligaments)

o   Ex. Distal tibiofibular joint

§  Interosseous membrane connecting radius and ulna.

3.   Gomphoses: peg in socket fibrous joints

·      Ex. Periodontal ligaments

  1. Synchondroses: bones held together by hyaline cartilage

·      Epiphyseal plates (temporary) --> becomes synostoses

  2. Symphyses: bones held together by fibrocartilage; act as shock absorbers

Synovial Joints:

six features

o   Articularcartilage: hyaline cartilage covers bone ends

o   Joint (synovial) cavity: space containing synovial fluid

o   Articular (joint) capsule: two-layered:

   (1) Fibrous capsule: outermost; continuous with periosteum.  

   (2) Synovial membrane: innermost; covers all internal joint surfaces except articular cartilages.

o   Synovial fluid: derived from blood flow in synovial membrane; reduces friction between articular cartilages; nourishes chondrocytes.

o   Reinforcing ligaments: found outside of the articular capsule.

o   nerves and blood vessels.

What functions to reduce friction between adjacent structures and is associated with

synovial joints?

o    Bursa: flattened sac containing synovial fluid; common where ligaments, muscles, skin, tendons, or bones rub together.

Joints are most stable when:

·      articular surgaces are large and fit closely together or the socket is deep.

·      ligaments are positioned to reinforce joint and prevent undesirable movements.

·      muscles have “tone”- most important stabilizing factor of most joints; extremely important in shoulder/knee joints and arches of foot.

-  Abduction: moving a limb away from the midline (^ angle along frontal plane)

- Adduction: moving a limb toward the midline (down angle along frontal plane)

-  Circumduction: moving a limb in the shape of a cone.

-  Rotation: bone turns around its long axis.

·      Supination: radius and ulna are parallel

·      Pronation: radius rotates over ulna

·      Dorsiflexion: lifting the foot at the ankle.

·      Plantar flexion: depressing foot at ankle. (ex. ballerina standing on her toes)

·      Inversion: sole of foot turns medially

·      Eversion: sole of foot turns laterally

·      Protraction: anterior movement in transverse plan

·      Retraction: posterior movement in transverse plan

·      Elevation: lifting a body part superiorly

·      Depression: lowering a body part

·      Opposition: touching

plane

hinge

pivot

condyloid

saddle

ball-and-socket

  articular surfaces are flat permit nonaxial gliding movement.

·      Ex. Intercarpal, intertarsal, and intervertebral joints.

rounded end of one bone protrudes  into some type of ring; permit uniaxial rotation

-ex. proximal radioulnar and atlas/axis joints

oval articular surface of one bone fits into an oval depression in another; permit biaxial flexion, extension, abduction, adduction and circumduction

ex. metacarpophalangeal (knuckle) joints

articular sufaces have both convex and concave areas; permit biaxial flexion, extension, abduction, adduction, and circumduction

-ex. carpometacarpal joint

-thumb

convex head of one bone articulate with cuplike socket of another; permit multiaxial movements

ex. shoulder and hip joints

§  Sprains: stretched or torn joint ligament; healing is slow (poorly vascularized)

§  Cartilage Tears: healing does not occur (Avascular)

§  Dislocations (luxations): bones are forced out of alignment.

inflammation of a bursa; caused by a blow or friction; treated with rest, ice and inflammatory drugs.

inflammation of tendon sheaths; caused by overuse; treated with rest, ice and inflammatory drugs

 inflammation or degeneration of joints; caused by pain, stiffness, and swelling

·      Acute (short-term): forms usually result from bacterial infection; treated with antibiotics.

·      Chronic (long-term) forms include osteoarthritis, rheumatoid arthritis, and gouty arthritis.

• autoimmune disease involving sever inflammation of the joints
• most crippling form; joint movement restricted;  severe pain, and in severe cases ankylosis (fusion of bone ends)
• many joints affected at the same time and bilaterally

-Current treatment includes:

* immunosupressants (methotrexate)

*drugs that neutralize inflammatory chemicals (Enbrel and Remicade)

*Joint prostheses 

o   joint inflammation caused by the deposit of urate salts in soft joint tissues

-  More common in males; tends to run in families

-  usually affects one joint (base of great toe)

   Osteoarthritis (OA)

• progressive degeneration of articular cartilages
• most common form; rarely crippling
• affected individuals experience stiffness on arising and crepitus (crunching sound
• glucosamine and chondrotin sulfate MAY help preserve articular cartilage

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