Joints

Chapter 9

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

• 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

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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

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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

• Rotator cuff– Tendons of muscles

• Five principal ligaments– Glenohumeral (3)– Coracohumeral– Transverse humeral

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The Knee Joint• Tibiofemoral joint

• Two intracapsular ligaments– Acl, pcl

• Two extracapsular ligaments– Lateral collateral, medial

collateral

• Two menisci– Lateral and medial

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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

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