Joints

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Joints
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• Articulations of bones
• Functions of joints
• Hold bones together
• Allow for mobility
• Ways joints are classified
• Functionally
• Structurally

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Functional Classification of Joints

• Synarthroses (synarthrotic joints)
• immovable joints, most fibrous joints
• Amphiarthroses (amphiarthrotic joints)
• slightly movable, mostly cartilaginous joints
• Diarthroses (diarthrotic joints)
• freely movable joints
• Synovial joints

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Synarthrosis (immovable)

• Sutures - Fibrous joint
• Ex. found between bone of the skull
• Gomphosis Fibrous joint
• Cone-shape peg fits into socket
• Ex. Roots of teeth in the alveoli (socket) of
  maxillae and mandible
• Synchondrosis Cartilaginous joint
• Hyaline cartilage is connecting material
• Joint eventually replaced by bone
• Ex. Epiphyseal plate and joints between the rib
  and the sternum

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Gomphosis
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Amphiarthroses

• Syndesmosis
• Like suture but has more fibrous tissue between
  the bones
• Joints are not as tight (permits more
  flexibility)
• Distal end of tibia and fibula
• Symphysis (growing together)
• Cartilaginous joint
• Connecting material is a broad, flat disc of
  fibrocartilage
• Intervetebral joints and pubic symphysis

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Diarthrosis

• movable
• Has synovial cavity or joint separating bones
• Has articular cartilage covers the surface of
  articulating bones
• Reduces friction and helps absorb shock

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Structural Classification of Joints

• Fibrous joints
• Generally immovable
• Cartilaginous joints
• Immovable or slightly movable
• Synovial joints
• Freely movable

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Fibrous Joints

• Bones united by fibrous tissue
• Examples
• Sutures
• Synostosis bony joint synarthrosis
• Ex. Frontal suture
• Syndesmoses
• Allows more movement than sutures
  amphiarthrosis
• Ex distal end of tibia and fibula
• Gomphoses
• Fibrous joint synarthrosis
• Teeth in alveoli

Figure 5.27ab
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Cartilaginous Joints

• Bones connected by cartilage
• Synchondroses (hyaline cartilage) synarthrosis
• Ex. costal cartilage and epiphyseal plate
• Symphyses (fibrocartilage sandwiched between
  hyaline cartilage) amphiarthrosis
• Ex. intervetebral disks and symphysis pubis

Figure 5.27de
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Synovial Joints

• Articulating bones are separated by a joint
  cavity
• Synovial fluid is found in the joint cavity

Figure 5.24fh
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Features of Synovial Joints

• Articular cartilage (hyaline cartilage) covers
  the ends of bones
• Joint surfaces are enclosed by a fibrous
  articular capsule
• Have a joint cavity filled with synovial fluid
• Ligaments reinforce the joint

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Structures Associated with the Synovial Joint
(reduce friction)

• Bursae flattened fibrous sacs
• Lined with synovial membranes
• Filled with synovial fluid
• Not actually part of the joint
• Tendon sheath
• Elongated bursa that wraps around a tendon

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The Synovial Joint
Figure 5.28
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Supination and pronation only refers to the
movement of the hand.
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• Condyloid and saddle joints
• Very similar but slightly different in shape
• Movements
• Flexion, extension, adduction, abduction,
  circumduction ( a combination of the four)

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The axes for these movements run bilaterally
through the ankle.
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Other movements

• Elevation to raise a part
• Depression to lower a part
• Protraction to move a part forward
• Retraction to move a part backward
• You can elevate and depress many parts
• Scapula, pelvis, jaws, etc.
• These can also protract and retract

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The shoulder joint

• Humeroscapular or glenohumeral joint
• Multiple ligaments help to hold the humerus in
  place
• Primary structural support is the rotator cuff (a
  group of muscles)

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Elbow Joint

• Humerus, ulna, and radius
• Has pivot joint between the capitulum of the
  humerus and the head of the radius
• A hinge joint whose axis runs bilaterally through
  the trochlea

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The Hip Joint

• Coxal joint
• Ball and socket joint between the head of the
  femur and the acetabulum of the hip bone
• Has deep fossa which supports the tremendous
  force placed on it

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The Knee Joint

• Most complex and the largest joint
• Has three joints within a single synovial cavity
• Laterally tibiofemoral joint (lateral condyle
  of femur, lateral meniscu, lateral condyle of
  tibia) modified hinge joint
• Medially tibiofemoral joint (medial condyle of
  femur, medial meniscus, medial condyle of tibia)
  modified hinge joint
• Intermediate patellofemoral joint planar joint

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Inflammatory Conditions Associated with Joints

• Bursitis inflammation of a bursa usually caused
  by a blow or friction
• Tendonitis inflammation of tendon sheaths
• Arthritis inflammatory or degenerative diseases
  of joints
• Over 100 different types
• The most widespread crippling disease in the
  United States

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Clinical Forms of Arthritis

• Osteoarthritis
• Most common chronic arthritis
• Probably related to normal aging processes
• Rheumatoid arthritis
• An autoimmune disease the immune system attacks
  the joints
• Symptoms begin with bilateral inflammation of
  certain joints
• Often leads to deformities

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Clinical Forms of Arthritis

• Gouty Arthritis
• Inflammation of joints is caused by a deposition
  of urate crystals from the blood
• Can usually be controlled with diet

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Other diseases

• Lyme disease
• Caused by deer ticks
• Afflicts the knee, ankle, hip, elbow, or wrist
• Arthritis is the main complication in advance
  stages of disease

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Joint injuries

• Sprain - twisting of the joint, often with
  accompanying stretching and tearing of ligaments
• Strain pulling of a muscle tendon and other
  connective tissue in muscles, but not joint tissue

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Joint injuries

• Luxation is a dislocation where a bone such as
  the humerus or femur pulls away from its position
  in the socket of the joint
• Separation occurs when fibrous tissue in a
  syndesmoses stretches or tears

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Aging and Joints

• Results in decreased production of synovial fluid
• Articular cartilage thins down
• Ligaments shorten lose flexibility

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Arthroplasty

• Surgical replacement of severely damaged joints
  with artificial joints
• Most commonly replaced hips, knees, shoulders
• Partial hip replacement involves the femur
• Total hip replacement involves both acetabulum
  and head of the femur

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