Chapter 9
Joints
Objectives
• Be able to define an articulation and arthrology
• Know the four main categories of articulations
and their sub categories
• Understand how a lever works and what
mechanical advantage is
• Be able to describe selected joints of the body
Articulations
• Any point where two bones meet
• Arthrology
– Science of joint structure, function, and dysfunction
• Classified into four main categories
– Bony
• Synostosis
• Immovable joint formed when two separate bones fuse to form one
• Ex. Frontal, mandible, epiphyseal line
– Fibrous
– Cartilaginous
– Synovial
Fibrous
• Synarthrosis
• Adjacent bones bound by collagen fibers that
penetrate into both bones
pc.maricopa.edu
• Three kinds
– Sutures
• Serrate, lap, and plane
– Gomphoses
• Teeth in socket
– Syndesmoses
• Bones held by longer collagen fibers that allow for a greater range
of motion
– Interosseous membrane between ulna and radius
Cartilaginous
• Amphiarthrosis
• Two bones are linked by cartilage
• Two types
– Synchondroses
• Bones joined by hyaline cartilage
– Epiphyseal discs
– Symphysis
• Bones are joined by fibrocartilage
– Pubic symphysis, intervertebral discs
Synovial Joints
• Diarthrosis
• Articulation of bones surrounded by
a joint capsule
– Articular hyaline cartilage at ends of
bones
– Synovial fluid
– Articular disc and meniscus
– Bursa and tendon sheaths
• Exhibit the widest range of motion
zoology.ubc.ca
Lever Systems
• Enhance speed or power of limb movements
– Rigid, elongated object that pivots on a fixed point
called the fulcrum
– forces – resistance and effort
• Long bones and joints
• Mechanical advantage
– Ratio of output force to input force
– MA = LE/LR
– Lever can provide one of two types of advantages
• Exert more force on the object than what is being applied to
the lever
• Move the resistance arm farther or faster than the effort
arm
Lever Systems
• Mechanical advantage
– If > 1.0
• Lever produces more force, but less speed and
distance, than force applied to it
– High mechanical advantage, high power
– If < 1.0
• Lever produces more speed or distance, less force than
force applied to it
– Low mechanical advantage, low power
Types of Levers
Classes of Synovial Joints
• Six types based on shape of
articular surface and degree of
mobility
– Ball and socket
• Shoulder and hip joints
• Wide range of motion
– Condylar (ellipsoid)
• Radiocarpel joint,
metacarpophalangeal
– Saddle
• Trapezialmetacarpal joint
• Sternoclavicular joint
– Plane (gliding)
• Carpals and tarsals, vertebral articular
processes
– Hinge
• Knee and elbow
– Pivot
• Atlantoaxial and radioulnar joints
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Movements of Synovial Joints
• Flexion and extension
• Abduction and adduction
• Elevation and depression
• Protractions and retraction
• Circumduction
• Rotation
• Pronation and supination
The Shoulder Joint
• Glenohumoral joint
• Shallow joint, allows wide range of
motion
– Glenoid labrum
• Tendon of long head of bicep brachii
aftabphysio.blogspot.com
• Rotator cuff
– Tendons of muscles
• Five principal ligaments
– Glenohumeral (3)
– Coracohumeral
– Transverse humeral
aidmypain.com
The Knee Joint
• Tibiofemoral joint
• Two intracapsular ligaments
– Acl, pcl
• Two extracapsular ligaments
– Lateral collateral, medial
collateral
• Two menisci
– Lateral and medial
badknees.net
The Ankle Joint
• Talocrural joint
– Two articulations
• Tibia and talus
• Fibula and talus
• Anterior and posterior tibiofibular ligaments
– Binds tibia to fibula
• Medial (deltoid) ligament
– Binds tibia to foot
• Lateral (collateral) ligaments
– Bind fibula to foot
medical-dictionary.thefreedictionary.com
cedars-sinai.edu
chiropractic-books.com