7/27/2019 [OS 203] Basic Biomechanics of Musculoskeletal System.pdf 1/3


9th Centuryo Anatomy being practiced by priests in catacombs

o  Ironic because the Catholic Church had condemned


o Sick people would go to priests to be healed

  Several priests though to study human anatomy to

understand the condition of the sick.


 to 11th


o Proliferation of anatomy studies by Arab Muslims, which

were much more advanced than anything seen in the west

at the time

o The Holy War during the time of Pope Urban III destroyed

many anatomical documents produced by the Arab


15th to 16th Century

o Leonardo di ser Pieroda Vinci (1452-1519)

  One of the greatest anatomists of his time

  Studied anatomy to improve the quality of his drawings

of the human form

  Was interested primarily in the kinematics of bone and


  Understood that there were several groups of muscles

that were more important than others

o Andres Vesalius (1514-1564)

  A doctor by training

  “ De HumanisCorporisFabrica” in 1543

First human atlas of the western world

4 copies remain today

Early 20th


o Up until early 1900s, the mark of a good doctor was the

number of dissections you were able to perform

o Became more difficult to maintain because of the lack of


  Grave robbing became widespread

o There were calls to minimize the role of anatomy in the

study of medicine

o 1916: Sir John Bechtold

  “It is better to have forgotten everything about anatomy

than never having to learn it at all” 

AAxxiiaall aanndd AAppppeennddiiccuullaarr SSkkeelleettoonn 11.. AAxxiiaall SSkkeelleettoonn 

o Bones of the skull, neck, spinal column, and ribcage

22.. AAppppeennddiiccuullaarr SSkkeelleettoonn 

o Bones of the pectoral and pelvic girdles and their

respective appendages

FFuunnccttiioonnss oof f  tthhee SSkkeelleettaall SSyysstteemm 11.. PPrroovviiddeess aanndd IInnttrriiccaattee FFlleexxiibbllee NNeettwwoorrkk 

o The adult human is composed of 306 bones but still

manages to be very flexible

22.. PPrrootteeccttss VViittaall OOrrggaannss 

o Skull protects the brain

o Ribs protect the lungs and heart

o Pelvis protects the reproductive organs

33.. PPrroodduucceess BBlloooodd 

44.. PPrriimmaarryy RReeppoossiittoorryy oof f  CCaallcciiuumm 

o Big “refrigerator” of calcium 

55.. PPrroovviiddeess LLeevveerr AArrmmss 

o Discussed in Biomechanics portion

66.. PPrroovviiddeess EEf f f f iicciieenntt LLooccoommoottoorryy MMeecchhaanniissmm 

77.. PPrroovviiddeess EEf f f f iicciieenntt EEnneerrggyy AAbbssoorrbbiinngg MMeecchhaanniissmmss o Shock is distributed to throughout the skin, muscles, and


88.. EEnnhhaanncceess EEnneerrggyy DDiissssiippaattiioonn 

CCoommppoonneennttss oof f  tthhee MMuussccuulloosskkeelleettaall SSyysstteemm 

11.. BBoonnee 

22.. MMuussccllee 

o The origin of the muscle must be in a different bone than

the insertion

o This allows movement to occur

o Exception: Subclavius Muscle which originates and inserts

into the clavicle because it is only used as a cushion to

protect the branchial plexus from the clavicular bone.o Tendons attach muscles to bones

33.. LLiiggaammeennttss 

o Attach bones together in joints (various degrees of


o 2 Types of Ligaments found in a Ginglymus joint (Ex:

Elbow) – Capsule and Collateral ligaments 

o Capsule 

  Found covering the articular surfaces of bones in the


  Composed of hyaline cartilage

  Contains synovial fluid (hyaluronic acid) for lubrication

o Collateral ligaments 

  Stabilizes the joint by providing support to the lateral

and medial sides of the joint  Medial Collateral Ligament: Resists Valgus (from

outside) stress.

  Lateral Collateral Ligament: Resists Varus (from inside)





Types of Joints (1st

  Degree: According to Movement, 2nd


According to Structure)


o  Synarthroses : Immovable joints

  Sutures: fibrous joint that connect the flat bones of the skull

o  Amphiarthroses: Slightly movable joints

  Gomphoses: fibrous joint that keeps teeth in sockets

  Syndesmoses: fibrous joint that connect apposed bones to each

other through an interosseus membrane between the radius

and the ulna

  Synchondroses: temporary cartilaginous joint found in

epiphyseal plates. Eventually these joints harden to become

immovable in adults.

  Symphyses: permanent cartilaginous joints in the pubic

symphisis and in the vertebral column

o  Diarthroses (Synovial Joints): Freely movable joints

  Arthrodial joint (plane joint): Allow gliding or sliding motions

only (Ex: Intercarpal joints)

I.  History of AnatomyII.  Architecture of the Musculoskeletal System

A.  Axial and Appendicular Skeleton

B.  Functions of the Skeletal System

C.  Components of the Musculoskeletal system

D.  Joint Stabilization

E.  Planes and Action Class Movements of the Body

III.  Biomechanics

A.  What is Biomechanics?

B.  The Body is a Set of Lever Mechanisms

C.  Biochemical Factors Affecting Musculoskeletal System

D.  Afflictions of the Human Body


Dr. Rafael Bundoc

7/27/2019 [OS 203] Basic Biomechanics of Musculoskeletal System.pdf 2/3


JJooiinntt SSttaabbiilliizzaattiioonn 

11.. SSttaattiicc SSttaabbiilliizzeerrss 

o Joint Capsule

o Ligaments

o Osseous Architecture

  The more surface area between bones, the more stable

the joint should be.

  Knee Joint VS Ankle Joint: Knee bones are larger, but the

ankle joint is more stable because there is more surface

area between the bones of the ankle.

 This view of stability does not take into considerationother stabilizers

o Negative Intra-articular pressure

  Synovial fluid was a net negative pressure

  If you stab someone in the knee you will hear a soft hiss

22.. DDyynnaammiicc SSttaabbiilliizzeerrss 

o Muscles

o Tendons

PPllaanneess aanndd AAccttiioonn CCllaassss MMoovveemmeennttss oof f  tthhee BBooddyy 

11.. CCoorroonnaall PPllaannee 

o Orientation: Anterior/Ventral or Posterior/Dorsal

o Flexion: Anterior/Ventral Movement

o Extension: Posterior/Dorsal Movement

o Pronation: Internal rotationo Supination: External rotation

o Abduction: Moves away from the plane

o Adduction: Moves towards the plane

22.. SSaaggiittttaall PPllaannee 

o Orientation: Lateral or Medial and Left or Right

o Abduction: Moving away from the median plane

o Adduction: Moving towards the median plane

o Elevation: Raising a part superiorly (Ex: elevating


o Depression: Inferior movement (Ex: slumping shoulders)

o  Inversion: Turning medially (Ex: turning the sole towards

the middle)

o Eversion: Turning laterally (Ex: turning the sole outwards)

33.. AAxxiiaall//CCrroossss SSeeccttiioonnaall//TTrraannssvveerrssee PPllaannee o Orientation Up/Superior or Down/Inferior

o External Rotation*

o  Internal Rotation*

o *Must indicate point of reference

FFiigguurree 11.. PPllaanneess oof f  tthhee BBooddyy 

Science on the internal and external forces acting on the

human body and the effects produced by these forces

11.. 11sstt CCllaassss LLeevveerr MMeecchhaanniissmmss 

o Fulcrum between the load and the force

FFiigguurree 22.. FFiirrsstt CCllaassss LLeevveerr 

22.. 22nndd CCllaassss LLeevveerr MMeecchhaanniissmmss 

o Load between fulcrum and force

FFiigguurree 33.. SSeeccoonndd CCllaassss LLeevveerr 

33.. 33rrdd CCllaassss LLeevveerr MMeecchhaanniissmmss 

o Force between fulcrum and load







. TT





ssss LL





See last page for some examples of the lever mechanisms in

the body.

BBiioocchheemmiiccaall FFaaccttoorrss AAf f f f eeccttiinngg MMuussccuulloosskkeelleettaall 


11.. OObb j jeecctt:: MMaatteerriiaall PPrrooppeerrttyy 

o Bone Composition

  Mineral (70%)

Inorganic Phase

Hydroxyapatite (95%) and Impurities (5%)

  Matrix (25%)

Organic Phase

Collage/proteins (98%) and Bone cells (2%)

  Water (5 to 8%)

22.. OObb j jeecctt:: SSttrruuccttuurraall PPrrooppeerrttyy 

o Osteon

  Histological unit of bone

  Haversian canals and hydroxyapatite crystal lamellae

  Volkmann’s canals connect Haversian canals 

o Osteocytes: Found within lacunae 

o Osteoblasts 

  Responsible for the formation of bone

  Active in the bone borders

o Osteoclasts 

  Receive signals from osteoblasts to resorb bone when

levels of blood calcium are low  Active in the bone borders

o Osteoprogenitor cells – Give rise to osteoblasts

o Acellular components 

  Calcium Hydroxyapatite alone is very brittle, which is

why organic matter (collagen and proteins) are

required to reinforce it.

o Osteoporosis: Due to the decalcification of bone

  Hallmarks: Stooping and Vertebral Compression



What is Biomechanics?

The Body is a Set of Lever Mechanisms

Continuation: Types of Joints

  Ginglymus joint (hinge joint): Allow flexion and extension only

(Ex: elbow and knee)

  Trochoidal joint (pivot joint): uniaxial rotary joint (Ex: Atlas-

axis joint)

  Ellipsoidal joint (condyloid joint): allows flexion, abduction,

adduction and circumduction (Ex: Wrist joint)

  Sellar joint (saddle joint): biaxial joint with concavoconvex

articulating surfaces (Ex: carpometacarpal joint of thumb)

  Spheroidal joint (ball and socket joint): multiaxial joints (Ex:

hip and shoulder)

7/27/2019 [OS 203] Basic Biomechanics of Musculoskeletal System.pdf 3/3


Figure 5. Vertebral Compression Fractures(Source: 

Figure 6. Stooping 

33.. LLooaadd:: TTyyppee oof f  LLooaadd 

o The amount of load is measured by Force

  Force = mass x acceleration

o Newton’s Third Law: For every force there is an equal

and opposite force

o This opposite force is called STRESS 

  Exemplified in the body by the synergistic andantagonistic muscle forces

  Reason for why you never have to worry about

keeping your arm in place

o Fractures occur when LOAD > STRESS

Figure 7. Types of Load

44.. LLooaadd:: LLooaadd RRaattee 

o Refers to the speed of the application of the load

o Ex: If someone shoots you, the load rate of the bullet

overcomes the relatively low load magnitude.

55.. LLooaadd:: MMaaggnniittuuddee oof f  LLooaadd 

o The greater the load, the more difficult to counteract it

  Calcium Hydroxyapatite alone is very brittle, which is

why organic matter (collagen and proteins) are

required to reinforce it.

o Osteoporosis: Due to the decalcification of bone  Hallmarks: Stooping and Vertebral Compression


AAf f f f lliiccttiioonnss oof f  tthhee HHuummaann BBooddyy 

11.. TTrraauummaa 

22.. CCoonnggeenniittaall DDeef f oorrmmiittiieess 

33.. IInnf f eeccttiioonn 

44.. NNeeooppllaassmm 

55.. DDeeggeenneerraattiioonn 


REVIEW QUESTIONS1. A flexion usually involves a movement in the anterior or

ventral side of the body. Give one joint that does flexion

on the posterior or dorsal side.

2. Differentiate the structure (as viewed under the light

microscope) and function of osteoblast and osteoclast.

3. The ankle joint is a _____ class lever while the shoulder

 joint is _____ class lever.

4. Maglista ng hindi bababa sa 15 katao na kilala mong nalate

sa lecture na ito.

Table 2. Examples of Lever Mechanisms in the Body



Hip Joint Acetabulo-femoral joint Weight of the body superior to


Trochanter End of greater trochanter to


Elbow Extension Elbow Weight being lifted Biceps Forearm

Spine Dorsal end of vertebral


Weight of body anterior to

spinal column

Postural muscles Across the joint

Knee Knee joint Weight of the body Leg abduction Edge of tibia to center of the



Ankle Joint Ball of the foot Body weight Action of gastrocnemius


Length of foot


Shoulder Joint Shoulder Joint Hand Action of deltoid and

abductor muscles


Elbow Flexion Elbow Joint Hand Biceps Radius and Ulna

Phalanges Inter-phalangeal joint Phalanges Tendons of flexor muscles Phalanges

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