human joints

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Joints and Their Classification

• Arthrology = study of the joints• Kinesiology = study of musculoskeletal

movement• Classified by freedom of movement– diarthrosis (freely movable)– amphiarthrosis (slightly movable)– synarthrosis (little or no movement)

• Classified how adjacent bones are joined – fibrous, cartilaginous, bony or synovial

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Bony Joint (Synostosis)

• Gap between two bones ossifies– frontal and mandibular bones in infants– cranial sutures in elderly– attachment of first rib and sternum

• Can occur in either fibrous or cartilaginous joint

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Fibrous Joints (Synarthrosis)

• Collagen fibers span the space between bones– sutures, gomphoses and syndesmoses

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Fibrous Joint -- Gomphoses

• Attachment of a tooth to its socket

• Held in place by fibrous periodontal ligament– collagen fibers attach

tooth to jawbone• Some movement while

chewing

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• Two bones bound by ligament only– interosseus

membrane• Most movable of fibrous joints• Interosseus membranes unite radius to ulna and

tibia to fibula

Fibrous Joint -- Syndesmosis

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Cartilaginous Joint -- Synchondrosis

• Bones are joined by hyaline cartilage– rib attachment to

sternum– epiphyseal plate in

children binds epiphysis and diaphysis

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Cartilaginous Joint -- Symphysis

• 2 bones joined by fibrocartilage– pubic symphysis and

intervertebral discs• Only slight amount

of movement is possible

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Synovial Joint

• Joint in which two bones are separated by a space called a joint cavity

• Most are freely movable

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General Anatomy

• Articular capsule encloses joint cavity– continuous with periosteum– lined by synovial membrane

• Synovial fluid = slippery fluid; feeds cartilages• Articular cartilage = hyaline cartilage covering the joint surfaces• Articular discs and menisci

– jaw, wrist, sternoclavicular and knee joints– absorbs shock, guides bone movements and distributes forces

• Tendon attaches muscle to bone• Ligament attaches bone to bone

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Tendon Sheaths and Bursae

• Bursa = saclike extension of joint capsule • Tendon sheaths = cylinders of connective tissue lined

with synovial membrane and wrapped around a tendon

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Components of a Lever• A lever is a rigid object that swings on a fixed point

called a fulcrum• Movement occurs when effort overcomes

resistance– resistance arm and effort arm are described relative to

fulcrum

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Mechanical Advantage of a Lever

• Two kinds of levers– lever that helps increase output of force• human moving a heavy object with help of crowbar

– lever move object further and faster• movement of row boat with paddle

• Types of levers produce either increase in speed or force

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First-Class Lever

• Has fulcrum in the middle between effort and resistance• Atlanto-occipital joint lies between the muscles on the back of the

neck and the weight of the face

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Second-Class Lever

• Resistance between fulcrum and effort• Resistance from the muscle tone of the temporalis muscle

lies between the jaw joint and the pull of the digastric muscle on the chin as it opens the mouth quickly

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Third-Class Lever

• Effort between the resistance and the fulcrum– most joints of the body

• The effort applied by the biceps muscle is applied to the forearm between the elbow joint and the weight of the hand and the forearm

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Range of Motion• Degrees through which a joint can move• Determined by– structure of the articular surfaces– strength and tautness of ligaments, tendons and

capsule• stretching of ligaments increases range of motion• double-jointed people have long or slack ligaments

– action of the muscles and tendons• nervous system monitors joint position and muscle tone

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Axes of Rotation

• Shoulder joint has 4 degrees of freedom = multiaxial joint

• Other joints – monoaxial or biaxial

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Types of Synovial Joints

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Ball-and-Socket Joints

• Smooth hemispherical head fits within a cuplike depression– head of humerus into glenoid

cavity of scapula– head of femur into acetabulum of

hip bone

• Multiaxial joint

Distal bone can move around a center in an indefinite number of axes. Main movements are flexion-extension, adduction-abduction, axial rotation and circumduction.

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Condyloid (ellipsoid) Joints

• Oval convex surface on one bone fits into a similarly shaped depression on the opp. bone– radiocarpal joint of the wrist – metacarpophalangeal joints at the

bases of the fingers

• Biaxial joints

Distal bone has an ovoid articular surface and is received into an elliptical cavity, wich makes it impossible for the bones to do axial rotation. So main movements here are flexion-extension, adduction-abduction and circumduction.

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Saddle Joints• Each articular surface is shaped like a

saddle, concave in one direction and convex in the other– trapeziometacarpal joint at the base of

the thumb

• Biaxial joint– more movable than a condyloid or

hinge joint forming the primate opposable thumb

The saddle joint consists of two opposing surfaces which allows flexion, extension, adduction, abduction, and circumduction, but no axial rotation.

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Gliding Joints

• Flat articular surfaces in which bones slide over each other

• Limited monoaxial joint

The main movements are flexion-extension and rotation. wrist

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Hinge Joints

• One bone with convex surface that fits into a concave depression on other bone– ulna and humerus at elbow joint– femur and tibia at knee joint– finger and toe joints

• Monoaxial joint

Knee,elbow, fingers

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Pivot Joints• One bone has a projection that

fits into a ringlike ligament of another

• First bone rotates on its longitudinal axis relative to the other– atlantoaxial joint (dens and atlas)– proximal radioulnar joint allows

the radius during pronation and supination Atlas and Axis, Proximal

Radio-Ulnar articulation

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Flexion, Extension and Hyperextension

• Flexion decreases the angle of a joint

• Extension straightens and returns to the anatomical position

• Hyperextension = extension beyond 180 degrees

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Flexion, Extension and Hyperextension

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Abduction and Adduction

• Abduction is movement of a part away from the midline – hyperabduction – raise arm over back or front of head

• Adduction is movement towards the midline– hyperadduction – crossing fingers

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Elevation and Depression

• Elevation is a movement that raises a bone vertically– mandibles are elevated during biting and clavicles during a

shrug

• Depression is lowering the mandible or the shoulders

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Protraction and Retraction

• Protraction = movement anteriorly on horizontal plane– thrusting the jaw forward,

shoulders or pelvis forward• Retraction is movement

posteriorly

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Circumduction

• Movement in which one end of an appendage remains stationary while the other end makes a circular motion

• Sequence of flexion, abduction, extension and adduction movements– baseball player winding up for a

pitch

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Rotation• Movement on

longitudinal axis– rotation of trunk,

thigh, head or arm• Medial rotation

turns the bone inwards

• Lateral rotation turns the bone outwards

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Supination and Pronation• In the forearm and foot• Supination – rotation of forearm so that the palm

faces forward– inversion and abduction of foot

(raising the medial edge of the foot)

• Pronation– rotation of forearm so the palm faces

to the rear– eversion and abduction of foot

(raising the lateral edge of the foot)

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Movements of Head and Trunk

• Flexion, hyperextension and lateral flexion of vertebral column

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Rotation of Trunk and Head

• Right rotation of trunk; rotation of head

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Movements of Mandible

• Lateral excursion = sideways movement • Medial excursion = movement back to the midline– side-to-side grinding during chewing

• Protraction – retraction of mandible

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Movement of Hand and Digits

• Radial and ulnar flexion

• Abduction of fingers and thumb

• Opposition is movement of the thumb to approach or touch the fingertips

• Reposition is movement back to the anatomical position

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Movements of the Foot

• Dorsiflexion is raising of the toes as when you swing the foot forward to take a step (heel strike)

• Plantarflexion is extension of the foot so that the toes point downward as in standing on tiptoe

• Inversion is a movement in which the soles are turned medially• Eversion is a turning of the soles to face laterally

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The Humeroscapular Joint• Most freely movable joint in the body– shallowness and looseness – deepened by glenoid labrum

• Supported by ligaments and tendons– 3 glenohumeral, coracohumeral,

transverse humeral and biceps tendon areimportant joint stabilizer

• Supported by rotator cuff musculature– tendons fuse to joint capsule and

strengthens it– supraspinatus, infraspinatus, teres minor

and subscapularis, • 4 Bursae associated with shoulder joint

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Stabilizers of the Shoulder Joint

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Tendons of Rotator Cuff Muscles

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The Elbow Joint• Single joint capsule

enclosing the humeroulnar and humeroradial joints

• Humeroulnar joint is supported by collateral ligaments.

• Radioulnar joint is head of radius held in place by the anular ligament encircling the head

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Elbow Joint

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The Coxal (hip) Joint

• Head of femur articulates with acetabulum• Socket deepened by acetabular labrum• Blood supply to head of femur found in ligament of the

head of the femur Joint capsule strengthened by ligaments

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Hip Joint• Joint capsule

strengthened by ligaments– pubofemoral– ischiofemoral– iliofemoral

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Dissection of Hip Joint

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The Knee Joint• Most complex diarthrosis – patellofemoral = gliding joint– tibiofemoral = gliding with slight

rotation and gliding possible in flexed position

• Joint capsule anteriorly consists of patella and extensions of quadriceps femoris tendon

• Capsule strengthened by extracapsular and intracapsular ligaments

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Knee Joint – Sagittal Section

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Knee Joint – Anterior and Posterior Views

• Anterior and lateral cruciate ligaments limit anterior and posterior sliding movements

• Medial and lateral collateral ligaments prevent rotation of extended knee

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Knee Joint – Superior View

• Medial and lateral meniscus absorb shock and shape joint

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Cruciates

Cruciates

Cruciates

Cruciates

Patella

• TKA is one of the most successful and commonly performed orthopedic surgery.

• The best results for TKA at 10 – 15 yrs. compare to or surpass the best result of THA.

1- Cruciate retaining2- Cruciate substituting3- Mobile bearing4- Unicondylar

Classification

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Arthritis and Artificial Joints

• Rheumatoid arthritis is autoimmune attack on joint– antibodies attack synovial membrane, enzymes in

synovial fluid degrade the cartilage, bones ossify– remissions occur, steroids and aspirin control

inflammation• Arthroplasty is replacement of diseased joint

with artificial device called prosthesis

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Joint Prostheses