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 pc.maricopa.edu

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 = L E /L R – 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 iupucbio2.iupui.edu

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 aftabphysio.blogspot.com 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

chiropractic-books.com cedars-sinai.edu