Chapter 9: Joints

Question 1

What is a joint and how does it get its name?

Answer 1

• A joint (AKA articulation) is any point where two bones meet, whether or not the bones are moveable at that interface
• Joint name: typically derived from the names of the bones / bone marking involved

Question 2

What are the 3 major joint (functional) categories?

Answer 2

• Synarthrotic
  
  • immoveable
• Amphiarthrotic
  
  • amphiarthrotic
• Diarthrotic
  
  • freely moveable

Question 3

What are the 4 major (structural) joint categories?

Answer 3

• Bony joints
  
  • between them is bone
• Fibrous joints
  
  • Bones are bound by collagen fibers that emerge from one bone and penetrate into the other
• Cartilaginous joints
  
  • between them is cartilage
• Synovial joints
  
  • freely moving
  • between them is space (capsule and cavity)

Question 4

WHat are the different types of bony joints?

Answer 4

• Synostosis
  
  • immobile
  • gap between two joints ossifies and becomes one bone
  • E.g. light and right mandibular bones in infants, cranial sutures in elderly, attachment of rib to sternum in old age

Question 5

What are the different types of fibrous joints?

Answer 5

• Sutures
  
  • immobile or slightly mobile
  • short collagen fibers
  • Serrate (interlocking way lines)
    
    • coronal, sagittal, lambdoid sutures
  • Lap (squamos): overlapping beveled edges
    
    • temporal and parietal sutures
  • Plane (butt): straight
    
    • palatine process of the maxillae
• Gomphoses
  
  • attachment of a tooth to its socket
  • Held in place by periodontal ligament (collagen made)
  • Allows tooth to move a lit under stress of chewing
• Syndesmoses
  
  • two bones bound by long collagen fibers
  • mobile syndesmoses: interosseous membrane between radius and ulna
  • less mobile syndesmoses: between tibia to fibula

Question 6

What are the types of cartilaginous joints?

Answer 6

• Synchondroses
  
  • bones held together by hyaline
  • Epiphysial plates (temporary joints)
  • E.g. first rib attachment to sternum
• Symphyses
  
  • bones held together by fibrocartilage
  • e.g. pubic symphysis, bodies of vertebrae joined by intervertebral discs
    
    • only slight movement between adjacent vertebrae

Question 7

What are some characteristics of synovial joints?

Answer 7

• These are often known as diarthrosis or diathrodial joints
• Two bones are separated by a joint (articular cavity) containing the lubricant synovial fluid (like an egg white)
• Most are free moveable
• Most are structurally complex
• They are most likely to develop painful disfunction
• They are most important joints for health professionals to understand

Question 8

What is the general anatomy of a synovial joint?

Answer 8

• Articular cartilage (very thin coating)
  
  • reduces friction and absorbs shock
• Joint (articular) cavity
• Synovial fluid
  
  • slippery lubricant in joint cavity
• Joint (articular) capsule
  
  • outer fibrous capsule, contains periosteum
  • Inner, cellular, synovial membrane

Question 9

What are accesory structures of a synovial joint?

Answer 9

• Fibrocartilage
  
  • articular disc between bones (e.g. temporomandibular joint)
  • Meniscus in knee
  • absorbs shock and pressure
  • improves fit together
  • stabilizes joints, reducing the chance of dislocation
• Tendon
• Ligament
• Bursa
  
  • fibrous sack filled with synovial fluid
  • located between muscles where tendons pass over bone or between bone and skin
  • cushion muscles, help tendons slide over joints, modifies direction of tendon pull
• tendon sheath
  
  • elongated cylindrical bursa wrapped around a tendon
  • in hand and foot

Question 10

How does exercise work with articular cartilage?

Answer 10

• Exercise warms synovial fluid
  
  • presses it like a sponge, in and out
  • synovial fluid is like blood replacement
• Cartilage then swells and provides a more effective cushion
• Repetitive compression exhanges fluid in and out of cartilage
  
  • exhange metabolic waste and nutrients/oxygen (like blood)
  • helps maintain health of cartilage longer

Question 11

What is range of motion (ROM) and what affects it?

Answer 11

• ROM is the degrees through which a joint can move
  
  • aspect of joint performance
  • physical assessment of a patient’s joint flexibility
• Determined by…. shape of articular surfaces
  
  • olecranon ulna fits into olecranon fossa of humerus
• Strength and tautness of ligaments and joint capsules
  
  • stretching of ligaments increases ROM
• Action of the muscles and tendons
  
  • nervous system monitors joint position and muscle tone
    
    • muscle tone: state of tension maintained in resting muscles

Question 12

What are the 6 classes of synovial joints and their general characteristics?

Answer 12

• Ball and socket joints
  
  • only multiaxial joints
  • hips, shoulder
• Condylar (ellipsoid) joints
  
  • oval convex surface of one bone fits into a complementary shaped depression on the other
  • biaxial (flexsion/extension and abduction/adduction usually)
  • radiocarpal joint, metacarpophalangeal joint, atlanto-occipital joint
• Saddle joints
  
  • both bones have articular surface shaped like a saddle, one is concave and the other convex
  • Biaxial
  • Trapeziometacarpal (opposeable thumb)
• Plane (gliding) joints
  
  • flat articular surfaces slide over each other
  • usually biaxial
  • intercarpal/tarsal, between articular processes of vertebrae
• Hinge joints
  
  • one bone with convex surface fits into concave depression of another bone
  • monoaxial
  • elbow, knee, joints within fingers and toes
• Pivot joints
  
  • a bone spins on its longitudinal axis
  • monoaxial
  • atlantoaxial joint (shaking head), radioulnar joint

Question 13

What is zero position?

Answer 13

the position of a joint when a person is in the standard anatomical position

(joint movements described as deviation from the zero position or returning to it)

Question 14

Describe the following movements: flexsion, extension, hyperextension, abduction, and adduction

Answer 14

• flexion: movement that decreases joint angle
  
  • common in hinge joints
• extension: movement that straightens a joint and returns the body to the zero position
• hyperextension: extension of a joint beyond zero position
• Abduction: movement of a body part in the frontal plane away from the midline of the body
• Adduction: movement in the frontal plane back toward the midline
  
  • hyperadduction: crossing fingers, crossing ankles

Question 15

Describe the following movements: elevation and depression, protraction and retraction, circumduction, rotation, supination and pronation

Answer 15

• elevation: movement that raises a body part vertically in the frontal plane
• depression: movement that lowers a body part in the same plane
• protraction: the anterior movement of a body part in the transverse plane
• retraction: posterior movement in the same plane
• circumduction: one end of an appendage remains stationary while the other end makes a circular motion
• rotation: movement in which a bone spins on its longitudinal axis (can be medial/internal or lateral/external)
• Supination: forearm movement that turns the palm to face anteriorly or upward
• Pronation: forearm movement that turns palm to face either posteriorly or downward

Question 16

Describe the following special movements: lateral flexion of the head, radial/ulnar flexion of the hand, opposition / reposition of the thumb, dorsiflexion/plantar flexion of the feet, inversion / eversion of the feet

Answer 16

• Lateral flexion of the head: tilting the head or trunk to the right or left at the midline
• Radial / ulnar flexion of the hand: tilting hand toward thumb/little finger
• Opposition/reposition of the thumb: moving thumb to touch tip of a finger, returning thumb to the zero position
• Dorsiflexion/plantarflexion: elevating toes / extending foot to stand on tip toe
• Inversion/eversion: soles are turned medially / soles are turned laterally

Question 17

What are the basic elements of the jaw joint (TMJ)?

Answer 17

• Temporomandibular joint (TMJ) is an articulation of the mandibular condyle of the mandible with the mandibular fossa of the temporal bone
• Synovial cavity is dvided into superior and inferior chambers by an articular disc
• Deep yawn or strenuous depression can dislocated TMJ
• Chronic dislocation sydnrome is common

Question 18

What are the basic elements of the shoulder joint?

Answer 18

• Glenhumeral joint–articulation of the glenoid cavity of scapula and the humerus
• Most freely moveable joint in the body
• Sacrifices stability for freedom of movement
• The joint is stabilized by tendons:
  
  • biceps brachii tendon
  • rotator cuff tendon (fused to joint capsule)
  • stabilized in all directions except inferior, so most dislocations are downward
  • ring of fibrocartilage (labrum) deepens glenoid cavity

Question 19

What are the basic elements of the elbow joint?

Answer 19

• Joint with two articulations:
  
  • humeroulnar joint (trochlea of humerus and trochlear notch of ulna)
  • Humeroradial joint: capitulum of humerus and head of radius
  • Both articulations closed in one joint capsule
• Also contains proximal radioulnar joint
  
  • Functions as a pivor joint, not a hinge
  • Head of radius fits into radial notch of ulna
  • Allows for pronation and supination

Question 20

What are the basic elements of the hip joint?

Answer 20

• The coxal joint: head of femur inserts into acetabulum of coxal bone
• More stable than shoulder
• Dislocations are rare
• ring of fibrocartilage (labrum) deepens acetabulum socket
• Some infants have congenital dislocation
  
  • stay in harness until acetabulum is deep enough for femur head

Question 21

What are the basic elements of the knee joint?

Answer 21

• Tibiofemoral joint: largest and most complex diarthrosis of the human body
• Primarily a hinge joint
  
  • Patellofemoral joint is a gliding joint
• Stabilized by quadriceps tendon in front and hamstring tendon (semimembranous muscle) in back
• Popliteal region is stabilized by extracapsular ligaments and intracapsular ligaments (cross each other to form an X)
  
  • Anterior cruciate ligament (ACL): prevents hyperextension of knee, common site of knee injury
  • Posterior Cruciate Ligament (PCL): prevents femur from sliding off tibia
• Has lateral meniscus and medial meniscus
  
  • C-shaped cartilages within joint capsule
  • absorb shock and prevent side to side rocking
  • joined by transverse ligament

Question 22

What are the most common knee injuries and what is arthroscopic surgery?

Answer 22

• The knee is high vulnerable to rotational and horizontal stress
• Most common injuries are within the menisci and Anterior Cruciate Ligament
• Knee heals slowly due to scanty blood flow
• Arthroscopy is a procedure in which the interior of a joint is viewed with a pencil-thin arthroscope
  
  • less tissue damage than regular surgery
  • recover more quickly
  • arthoscopic ACL repair: 9 months for full heal

Question 23

What are the basic elements of the ankle joint?

Answer 23

• Talocrural joint
  
  • Medial articulation: between tibia and talus
  • Lateral joint: between fibula and talus
  • both articulations contained within one joint capsule
• Malleoli of the tibia/fibula overhang the talus on either side and prevent side to side motion
• More restricted range of motion than wrist
• Calcaneal (Achilles) tendon: extends from calf muscles to calcaneas
• Sprains (torn ligaments and tendons) are common at the ankle

Question 24

What is arthritis and its types / components?

Answer 24

• Arthritis is a broad term for the pain and inflammation of joints
  
  • It is the most common crippling disease in US
  • Rheumatologists treat it
• Osteoarthritis: most common form
  
  • wear and tear (years of joint wear)
  • articular cartilage softens and degenerates
  • Bone crackling sounds called crepitus
  • bone spurs develop on exposed bone tissue (painful)
• Rheumatoid Arthritis
  
  • autoimmune attack against joint tissues
  • Misguided antibodies (rheumatoid factor) attack synovial membrane, articular cartilage degrades, joints begin to ossify
  • Remissions occur, steroids and aspirin control inflammation
• Arthroplasty: replacement of diseased joint with artifical device called prosthesis