Flashcards in Exam 1 Deck (275):
Biological Mechanics: ________
Study of systems in equilibrium and at rest: ________
Study of systems in motion: ________
Study of movement without consideration of the forces involved: ________
Study of movements and forces involved: _______
What are the 3 types of Motion?
Translatory: all the points on a segment travel in a parallel line
Rotary: a segment travels through an arc of motion around a single axis of rotation
Curvilinear: a combination of rotary and translatory motions
What are the 3 Axes of Motion?
Medial-Lateral: X axis
Anterior-Posterior: Z axis
Superior-Inferior: Y axis
What are the 3 Directions of Motion?
Sagittal Plane: Flexion/Extension
Frontal Plane: Abduction/Adduction
Transverse Plane: Medial/Internal Rotation
What is the difference between mass and weight?
Mass is the amount of matter composing the object (constant)
Weight is the force acting on the object due to gravity (always changing)
What are the Newton's 3 Laws?
Law of Inertia
F = ma
Every action has an equal and opposite reaction
What is the moment of inertia?
The measure of resistance to angular acceleration; affected both by the total mass and the distance that mass is from the COR
What is the equation for inertia?
I = mr2
What is Work? What is the equation?
The force required to move an object a certain distance
Work = force x distance
What is power? What is the equation?
The rate that work is being done
Power = work/time
What are the 2 types of energy?
Potential Energy and Kinetic Energy
What is difference between Global and Local Coordinate Systems?
Global: how an object moves with respect to the environment
Local: How an object moves with respect to another closely related object
What are the 4 components of a vector?
Point of Application
What is force?
A push or pull that results from physical contact between two objects
What is the resultant force?
One force that represents the multiple forces operating within the same system; any observed (or measured) force may be the result of 2 or more combined forces
What are orthogonal forces?
Component forces acting at right angles of each other to produce a resultant force
What are the 3 Force Systems?
Linear: a straight line
Planar: a specific plane
Space System: an area combining more than one plane
What are the 4 types of forces that can act within a force system?
Collinear: forces acting along the same straight line
Parallel: forces acting parallel to each other
Concurrent: forces that intersect at a common point
General: forces that are not collinear, parallel, or concurrent but still act within the are or upon the body
What are the 3 joint forces?
Tension = Traction = Distraction
What are the 5 main types of force?
Ground Reaction Force (stomp on the ground, and the ground stomps back)
Normal Force (perpendicular)
Force of Gravity: Always pulling towards the earth's center)
What is the Center of Gravity?
The hypothetical center of mass at which the force of gravity appears to act
What are the two types of Center of Gravity?
Overall COG: the point at which gravity acts on an object from the center of the earth
Segmental: Each part of the whole can be considered to have its own COG, and the interaction of each segment determines the overall COG
What are the average COGs for the 3 planes?
Frontal: at the level of S2
Transverse: anterior to the sacrum
What system is typically used when determining stability?
HAT Unit: Head, Arms, and Trunk
What is the relation between COG and Stability?
The closer the COG is to the BOS the higher the stability
What factors impact COG?
Gender Differences: Women typically have a lower COG compared to men (women's body mass: caudally distributed; men's body mass: cranially distributed)
Body types and hypertrophy/atrophy
Addition of external loads
What are the components of a lever?
Rigid bar: a body segment/whole limb
Force: created by a muscle contraction
Axis: anatomical joint
Resistance: usually an externally applied force
What is the Lever Arm (aka Moment Arm)?
The perpendicular distance from the point of the applied force on the rigid bar AoR
What two components of a lever have a lever arm?
Force and Resistance
What are the 3 classes of levers?
First Class: FAR
Second Class: ARF
Third Class: AFR
Explain the lever components of tricep extension.
Force: Triceps pulling on the olecranon
Axis: Glenohumeral Joint
Resistance: Mass of the hand and forearm
Explain the lever components of calf raises.
Axis: Metatarsal Heads
Resistance: Middle aspect of the arch of the foot
Force: Muscles of the deep and superficial Posterior Compartment
Explain the lever components of elbow flexion.
Axis: Humeroulnar Joint
Resistance: Halfway down the forearm and hand
What is mechanical advantage?
The ratio of muscle force lever arm (Tdf) to the resistive force lever arm (Tdr)
How do you determine which lever arm has the mechanical advantage?
If Tdf is longer than Tdr, then the muscle has the greater mechanical advantage
What are benefits and setbacks to 1st class levers?
Allow a large muscle mass on the opposite side of the axis from the resistance force
Usually have poor mechanical advantage
What are benefits and setbacks to 2nd class levers?
Have excellent mechanical advantage
Not common in the human body
What are benefits and setbacks to 3rd class levers?
Most common example in the body
Tendons are close to the AoR = small joint circumference
Allow the muscles to have greater lengthening/shortening = large joint movement
Resistance lever arm is longer making the muscles produce more force to overcome the resistance
Makes our body more slim and trim
What is torque? What is the equation?
Force applied through a lever results in a force that causes rotation about the axis of rotation
Torque = force x perpendicular distance
What direction is torque measured in?
Clockwise ( - direction)
Counterclockwise ( + direction)
*The AoR is the Z axis which protrudes outward (right hand rule)
What are the units of torque?
Newton-Meters (Nm): common unit in biomechanics literature
Foot Pounds (ft lbs): Isokinetics testing
Kilogram Centimeters (kg cm): clinical bicycle ergometer
What are the components of Force Couples?
Forces that are parallel and equal in magnitude
Points of application on opposite ends of a lever
Produce equal torques of the same sense, but act on different sides of the axis of rotation (steering wheel)
What is the biological definition of a force couple?
Two or more forces that act on a rigid body
Rotary motion is produced
Translational motion is minimized
What are two examples of force couples within the body?
Upward Rotation of the scapula (Contraction of the Upper Trap, Lower Trap, and Serratus Anterior)
Anterior Tilt of the pelvis (Contraction of the Erector Spinae, Iliopsoas, and Rectus Femoris)
What happens if, during Upward Rotation of Scapula, one of the three muscles is weaker?
The resulting action is more translational than rotational
What are the components of Biological torques?
Axis of Rotation: usually a joint center
Resistance Force: External force and/or gravity
Lever Arm of Resistance Force
Muscle Force: force produced by the muscle to counteract the resistance force
Lever Arm of muscle force
What is static equilibrium?
When there is no movement, because all torques are balanced
This can be used to find the magnitude of unknown forces that would be difficult to find otherwise
True or False: In Static Equilibrium, the mechanical advantage must be the same.
What are the 2 types of pulleys?
What is a Fixed Pulley?
A pulley that changes the action line of a force without changing its magnitude
What is the purpose of a fixed pulley?
Obtain a more favorable angle of pull
Provide a means of separating the muscle bulk from the point of application of the force (i.e. pulleys in the hands)
What is a Movable Pulley?
One end of the rope is fixed, and the applied force creates tension within the rope
The tension force in each strand is equal to the applied force
What is the purpose of a movable pulley?
Exercise weights on pulley arrangement
What is load?
Any force or combination of forces applied to the outside of a structure (external force)
What are the 2 types of load?
Total Load: force/total area (sum of all external forces)
Unit Load: the load expressed per unit of cross-sectional area (unit force or pressure)
What is stress?
The resistance of the intermolecular bonds in a substance to physical deformation by externally applied loads
What are the 3 types of stress?
What is tension stress?
The force in matter which resists being pulled apart
Resists being stretched or elongated
What is shear stress?
That force in matter which resists the sliding of one layer of matter on another
Commonly known as friction
Example: joint surfaces sliding on one another
What is compression stress?
The force in matter which resists being pushed together
Resists being shortened or crushed together
What is strain?
The physical deformation of matter resulting from a load acting upon the matter
What are the 3 types of strain?
What is tension strain?
Elongation; muscle and tendon elongates as you place it under tension stress (eccentrics)
Wat is compression strain
Shortening or thinning; articular cartilage, bone (little bit of movement)
What is shear strain?
Movement of one layer on another; Ligament tearing, bone on bone rubbing at a joint
What is Youngs' Modulus (E)?
A measure of material stiffness
The ratio of the stress (force) divided by the actual elastic strain (deformation)
Ε = σ / ε
What is the relationship between stiffness and material strength?
Stiffness does not equate to material strength
Chalk is stiffer, but steel is stronger
What is the relationship between the Modulus and Stiffness?
The larger the modulus, the stiffer the material
What is the hierarchy of Elasticity among bone, cartilage, muscle, and tendon?
In order of increasing deformity:
What is Hooke's Law?
For each unit of strain, there is a proportional increase in the internal stress
What is Elasticity?
The stiffness and ability of an object to recover energy or work fro a material
the ability of a material to return to its original shape after being deformed
What is the difference between a resilient and damped response?
If the recovery to the original shape is rapid, it is termed resilient (billiard ball, ligament)
If the recovery is slow, it is termed damped (articular cartilage, some plastics, IV discs)
What are the 2 types of deformation?
Creep and Plastic
What is creep deformation?
The capacity of a material to undergo slow, progressive deformation in response to continuous pressure (loading); if you stretch a hamstring over time, it will appear to be a little longer
What is plastic deformation?
A strain of a material which is permanent and will not recover when stress is released; goal during hamstring stretching is to achieve plastic deformation, and that stretch stays permanently
What is an object's proportional limit?
The point on the load/deformation curve at which the material's elongation in shape changes from linear to non-linear. This is synonymous with the term "Hookean limit"
What is an object's rupture point?
Elongation continues until the material finally breaks. The stress required for progressive deformation may actually decrease as the material progressively fails
What is an object's ultimate strength?
The maximum stress a material will sustain before fracturing or breaking
What is the difference between brittle and ductile behavior?
Brittle behavior has no plastic deformation before the break point
Ductile behavior has plastic deformation before the break point
What are the characteristics of an object with perfectly elastic loading/unloading behavior?
Stresses applied are less than the ultimate strength
Within the tested range, this material did not plastically deform and had no proportional limit
What is the elastic limit?
The stress below which the material returns to its original length but above which the material plastically deforms
True or false: The elastic limit is not always the same as the proportional limit.
What is an object's yield strength?
The stress at which a predetermined amount of plastic deformation occurs
For many engineering materials, what is the maximum allowed plastic deformation before it is considered damaged or compromised?
True or False: For biological materials (tendons, ligaments, etc.), the maximum allowed % change is similar.
What is viscoelasticity?
Property of a material to show sensitivity to rate of loading (stress) over rate of deformation (strain)
What is the correlation to loading rate, deformation, and stiffness?
Higher loading results in greater stiffness, but lower loading results in greater deformation (silly putty)
What is hysteresis?
A lag or delay in the response to a change in force
What does the gray area on the hysteresis curve represent?
The work in versus the mechanical work out (Energy is los in the form of heat)
What is ranking order for the ultimate strength of bone?
Compression, Tension, and Shear (Decreasing Order)
What is the order for Bone Modulus of Elasticity?
Long Axis, 30*, 60*, and Transverse (Decreasing order)
Similar to pushing down on soda straws
What is resilience?
The rapid rate of a material returning to its original shape
What is damping?
The slow rate of a material returning to its original shape (IV discs, articular cartilage, fibrocartilage)
What is toughness?
Ability of a material to withstand impact or to absorb high levels of energy before fracturing (steel and glass balls dropped on the floor; glass has more stiffness than bone/steel, but it has less toughness)
What is friction?
The tangential force acting between two bodies in contact which opposes motion
The resistance of objects to being moved on other objects
What are the 3 factors of friction?
How tightly the two forces are pressed together (compression forces)
The types of material in contact with each other and the roughness of the surfaces
The velocity at which movement takes place
What is Amonton's Law of Friction?
The force of friction is independent of the apparent bearing area
The force of friction is directly proportional to the applied load (eraser and book)
What is the difference between Static and Kinetic Friction?
Static Friction implies a non-slip condition
Kinetic Friction is characterized by a sliding of the contact surfaces
What is the equation for Static Friction?
fsmax = μs N
When does the maximal friction occur?
Right before slipping occurs
What is the equation for Kinetic Friction?
f = μk N
What is the direction of the Net Force in regards to the object?
Perpendicular to the surfaces
Describe the relationship between static and kinetic friction as the pulling force increases.
There is an equal and opposite force to the pulling force until the max static resistance of friction point is reached. After this point is reached, the object begins to move (max frictional resistance has been reached and it is turned into kinetic friction). The decreases a little bit, because speed and the kinetic friction curve are inversely related
What angle is equal to the coefficient of friction?
μ =Tan Θ
If the angle is increased, why does the weight begins to fall?
The orthogonal component of the object's weight (Fs) is pushing the block down the plane, because it exceeded Fsmax
What is Fluid Viscosity (Fluid Friction)?
A measure of the resistance of a fluid to flow (fluid shearing stress)
High Viscosity: Honey
Low Viscosity: Water
What is Laminar Flow?
Slower flowing rates in which the fastest flow is in the middle and the outer-most aspects drag against the wall/edge
What happens when you increase flow rate of a Laminar flowing object?
The flow rate reaches a critical point, and then turbulence is caused, resulting in dramatically increased resistance
What are the two types of fluids?
Newtonian: behave as you would expect
Non-Newtonian: Thixotropic and Dilatant fluids
What are the components of a Newtonian fluid?
The shearing stress is proportional to the shearing rate
Greater speed leads to greater resistance
What are the components of Non-Newtonian fluids?
The shearing stress is not proportional to the shearing rate
What are the components of a Thixotropic Fluid?
The fluid thickens with slower shear rates and thins with faster shear rates
Ex: synovial fluid
What are the components of a Dilatant Fluid?
The fluid thins with slower rates and thickens with faster rates
Ex: whole blood
At ejection, blood is so thick (acts like a bolus), but at the capillary beds it thins out and has less resistance
What are the two jobs of Connective Tissue?
Function mechanically to connect and bind cells and organs together
Give support to the body
What are the 4 types of Connective Tissue?
Supporting: bone and cartilage
Specialized: adipose tissue and hematopoietic tissue
Loose: "packing material" found between muscle sheaths, supporting epithelial tissue and neurovascular bundles
Dense: Irregular and regular
What is Connective Tissue made of?
Cells: maintain tissue via synthesis and degradation
Fibers: supply tensile strength and maintain shape (collagen: tensile strength; Elastin: extensibility; Reticulin: bulk and support, in smooth muscle)
Ground Substance: gel which binds to water (acts as a medium for diffusion and contributes to lubrication)
For a tissue or structure under load, what determines behavior?
Properties of its components
Relative amounts of its components
Orientation of its components (not only do you change the mix, but also the orientation of those mixtures)
What is the hardest of all connective tissues? And what are its 3 distinct arrangements?
Woven, Cortical, and Cancellous
What are the characteristics of woven bone?
Immature, disorganized fiber structure
The first bone formed in a fetus from the CT model
What are the characteristics of cortical bone?
Highly organized, mature bone which contains systems of osteons (Haversian systems); skeleton
What are the characteristics of cancellous bone?
Spongy, forms thin interconnecting plates (trabeculae) which act as struts to distribute forces
Found near joints
Great at absorbing compression
Spider web systems at the end of long bones
What is bone composed of?
Fiber organization similar to ligaments
Ground substance contains calcium phosphate crystals (stiff in compression)
Vascularized and innervated
Major reserve of calcium and phosphorus
Dynamic structure (Wollf's Law: bone changes shape to minimize stress)
What are the functions of bone?
Resist and redistribute compressive, tensile, and shear forces
Provide a system of levers with which movement can be accomplished
Able to replace their old Haversian Systems with newer ones to resist force
All of the above
What are the 3 types of cartilage?
Fibrocartilage: different in look, but similar in structure
Articular: specialized hyaline
What are the characteristics of fibrocartilage?
Similar to ligaments but with more ground substance (increased glycosaminoglycans)
Round lacunar pairs (where the cells lie)
Exs: pubic symphysis, IV Disc, junctions of tendon and bone, junction of ligament and bone, intra-articular meniscus
What is the function of fibrocartilage?
Tough, versatile, junction material with strength in multiple planes (fibers go in multiple directions)
Resists shearing stress and deformation
Compressive strength (menisci don't flatten when you step down)
What are the characteristics of hyaline cartilage?
Less fibrous than fibrocartilage (Type II)
Large volume of ground substance
Round, lacunar cells (territorial matrix)
Exs: costochondral junction, epiphysis of immature bone, entire skeleton of infant
What are the functions of hyaline cartilage
Provides flexible junction and has good compressive strength (resists deformation)
Provides interstitial growth
What are the characteristics of articular cartilage?
70-85% water; the rest is a combo of proteoglycans and Type II collagen
Specialized fibrous structure to resist shear stress
Large volume of ground substance provides viscoelasticity to distribute and dissipate force
Thin (3-5 mm)
Avascular, aneural, and alymphatic
Adult: nourished entirely by synovial fluid
Poor capacity to repair major damage
Organized in 4 zones, each with a different orientation and strucure
What are the characteristics of articular cartilage?
Viscoelastic: exhibits creep and stress relaxation
Permeability varies and affects the mechanical properties
Low coefficient of friction (slipper, 20xs slicker than glass on ice)
Describe the relationship between the mechanical properties and composition of articular cartilage.
Compressive stiffness is a function of GAG concentration, but not of collagen concentration
As the water content increases, the cartilage becomes less stiff
If the compression becomes too great, it can rupture, forcing water out
Deos mechanical cartilage fail as a result more from shear or tensile stress?
What mechanical factors increase the chances of developing OA?
Repetitive impulse loading
Surgical alterations of joint ligaments which may alter joint kinematics/stability (ACL repairs alter the ligament positively)
What is the difference between irregular and regular DCT?
Irregular: disorganized bundles (dermis)
Regular: dense, parallel fibers, resist tensile/traction forces well (tendons and ligaments)
What are the characteristics of regular DCT?
Fibrocytes and fibroblasts make up the cellular component (20%)
ECM makes up 80%
Collagen is the primary fibrous component of tendon and ligaments
Ground substance consists of: glycoproteins, proteoglycans, and water
What are the mechanical properties of tendons and ligaments of regular DCT?
Interaction between collagen and the ground substance
What are tendons composed of?
Collagen fibers oriented longitudinally and parallel (mostly type I and type II)
Low ground substance content (less proteoglycan concentration)
Flattened cells (fibroblasts small in number)
What is the function of tendons?
Longitudinal transmission of force (tension) - low slack
There's not much room for the fibers to expand, it's why they are so tightly packed
What are ligaments composed of?
Collagen fibers mostly oriented longitudinally(mostly type I and III)
Some elastin (Ex: ligamentum flavum)
Slightly more ground substance
What are the functions of ligaments?
Restrain joint motion
Less regular fiber orientation and increased ground substance provide better shock absorption than tendowns
What are the 6 regions of the stress-strain curve for tendons and ligaments?
Plastic Deformation (Microfailure: ligamentous strain)
Major Failure (Yield Point)
Complete Failure (Rupture Point)
What does the yield point mark on the Stress-Strain curve?
The end of the elastic region and start of the plastic region
What does the failure point indicate on the Stress-Strain curve?
The ultimate stress and ultimate strain
What are the zigzags on the Stress-Strain curve?
Parts of the ligament are failing, but others are still intact
Where on the Stress-Strain curve are clinical tests?
Why is it important to warm-up before being physically active?
Warming up takes the slack out of tissue
Which fibers are under the most tension?
Stiffness is dependent upon what under intermittent tensile load?
The rate of the load (viscoelastic behavior)
What anatomic/histologic factors determine stiffness and loading behaviors?
Composition of Ligamentum Flavum (between lamin, contains elastic fibers; slight passive tension; help keep quadruped head ups) and ACL (low levels of elastic tissue, stops tibia from gliding forward; don't want to wait around for it to be activated)
Where is the highest potential for injury?
Junction between fibrocartilage and bone
What are Sharpey's fibers?
Structures are stuck to the bone, and the bone grows around them
What surrounds the Sharpey's
Calcified fibrocartilage and fibrocartilage
How can tendons and ligaments fail?
Midsubstance ruptures or avulsion fractures (the structure pulls off the bone, usually with the bone fragment attached)
What factors impact failure mode?
Age, structure, and the speed of the applied force (angle of pull, stiffness)
What is the difference between constant length over time and constant tension over time?
Constant Length: apply only enough tensile fore to maintain a predetermined length (load relaxation: prop feet on ottoman)
Constant Tension: keep the tensile force the same regardless of length change (creep phenomenon: someone grabs your leg and stretches your ham, continues to apply tension)
How does age impact failure probability?
Gradual increase of crosslinks until age 20
Increased fiber bundle diameter
Increase in tensile strength until age 20
What physiological aspects change as someone ages?
Decreased collagen content and GAGs
Decreased tensile strength
What hormones impact connective tissue strength?
ACH, cortisone, and excessive cortisol
How does pregnancy and postpartum impact connective tissue?
Relaxin (form of estrogen) increases tissue laxity
Musculoskeletal system is vulnerable during this time
Birth control pills
What impacts do temperature have?
Above 37*C: viscoelastic properties (increased stress relaxation and creep) of tendons and ligaments
Up to 40*C: reduces failure load and strain in tendons
Above 40*C: tissues elongates more easily, stiffness decreases, less force is required to fail, narrows the window between elongation and damage
What are the impacts of increased stress on normal tissue?
Long duration/Increased amplitude: tissue elongation
Short duration/increased amplitude: increased stiffness
Increased ultimate strength and stiffness
Increased collagen diameter
Exercise may protect against weakening effects of inactivity
Excessive loads can have harmful effects
How does immobilization impact tissues?
8 Weeks: 40% loss of strength
5 months of reconditioning: 20% loss of strength
What are the biochemical and histological changes of immobilization?
Increased collagen turnover
Disorganized fiber alignment, alteration in collagen size, affect cross-links
What are the 4 stages of healing?
Hemorrhagic (first week after injury)
Inflammatory (first week after injury)
Proliferative (first week after injury)
Remodeling (lasts several months, but appears to never restore the pre-injury mechanical properties
How does early mobilization impact tissue healing?
Strengthens the unions
Reduces scar tissue adhesions (break it down to a previous state, then use force to try and get it to the ideal)
Why is force important for healing?
Without force, the fibers have no healing, and they have no direction for healing
Why is it important to not overstress damaged tissue?
Rehabilitation takes place within the limits of mechanical strength
Exceeding that mechanical strength of repair repeats back to the beginning of the injury cycle)
What is Rheumatoid Arthritis?
The connective tissue is exposed to too much inflammation resulting:
Increased joint laxity (lower levels to resist injury)
Increased joint deformation
Decreased tensile strength
What are the impacts of NSAIDS?
Increased tensile strength
Increased collagen content
What are the impacts of Steroidal Medication?
Blocks inflammatory process (glucocorticoids shouldn't be taken more then 1-2 times in 6 months)
Inflammatory process is necessary for tissue repair: lysosomes can't be released
Ethical considerations: you may feel better, but you are suppressing the healing process
What are the 3 types of bone?
Woven: Immature, cartilage fibers randomly distributed (not as strong as mature bone), more flexible than adult bone
Cortical: Mature, compact bone, can deal with high levels of compression
Cancellous: spongy bone/trabecular bone, immature skeleton and fractures, stress sharing struts, thin enough that osteons are not needed for blood supply
What are the functional units of bone?
Osteons: organized around central Haversian canals to provide diffusion of nutrients; joined to other osteons by cement lines
What kind of material is bone?
What impacts the mechanical properties of bone?
Direction and speed of loading
In a torsion force, where is the greatest stress on the bone?
Outside of the bone
What is the relationship between bone circumference and strength against torsion forces?
The larger the circumference the increased strength against torsion forces a bone has
Given its volume of tissue, what part of the tibia has better resistance to deformatioN?
Where do more torsion fractures take place? Why?
Distally; the lever arm is smaller distally
Explain the impact of the gastroc-soleus complex in absorbing/distributing forces
When the gastroc and soleus contract, they compress the tibia, eliminating the force in the posterior section. This increases the overall compression and increases the force in the anterior portion, because there is now a 0 force on the posterior side (not a neutral force)
What two factors can lead to compression bone fractures?
Excessive contraction forces or abnormally weak bone
What is the relationship between bone's modulus of elasticity, strength, and the loading rate?
As the loading rate increases, a bone's modulus of elasticity and strength also increase (bone is able to withstand greater stresses during traumatic, rapid loading when needed)
What aspects of bone begin to decrease after the age 35?
Stiffness, fracture toughness (resistance of bone to fracture), and bending strength
What factors, other than age, play an important role in bone loss?
Decreased activity and hormones (accelerated in women after menopause)
How do age/decreased activity levels impact the struts within bone?
The thickness of the struts can be increased with physical activity, but the number of struts decrease (combo of age and/or decreased activity levels
Even though the struts may become thicker, the decrease in the number of struts is not as good for distribution
Explain the fracture healing process.
Fractures form a callus that calcifies and then remodels
The strength of the callus increases as the bone mineral density increases (this is what determines Weight-bearing status)
What is the difference between an anatomical and physiological joint?
Anatomical: bone partners and the tissues which directly connect them (capsule, ligaments, intra-articular structures)
Physiological: anatomical joint with the surrounding tissue (skin, scars, etc.)
What are the 3 types of joints?
What is a Synarthrosis Joint?
A joint that is connected by fibrous tissue, but has no joint cavity
Little to know movement is present
E.x. skull sutures, teeth, interosseous membrane between the tibia and fibula (syndesmosis)
What is an Amphiarthrosis Joint?
A joint that is connected by hyaline cartilage (synchondrosis: costochondral and manubrio sternal joints) or fibrocartilage (symphysis: pubic symphysis, IV discs)
It has no joint cavity, but is is more mobile than Synarthrosis Joints
Slight movement present (disc will deform, pubic symphysis can move a bit between the rami)
Transmit and disperse forces between bones
What is a Diarthrosis (synovial) Joint?
A joint that is connected by a joint capsule, the joint cavity is present
E.x. glenohumeral joint, proximal tibiofibular joint, intercarpal joints
Free movement is present (although some are freer than others; surface and surrounding tissues impacts that)
What elements are always associated with diarthrodial (synovial) joints?
Articular capsule (synovial membrane = inner; fibrous capsule = outer; ligaments: thickenings of external CT fibrous capsule)
Blood vessels and nerves
What elements are sometimes associated with diarthrodial (synovial) joints?
Intra-articular discs or menisci (knee and TMJ, wrist, shoulder)
Peripheral labrum: fibrocartilage in the coccyfemoral joint
Fat pads: particularly larger joints (knee)
Synovial folds/plicae: folded spots (similar to a curtain), located in larger joints (knee), can cover a whole area or fold up into a smaller one
What is the difference between Joint and Instant centers?
Joint Centers (Joint axis): a close estimate of the actual joint axis
Instant Centers: the average joint axis is calculated for a specific arc of motion
What is the evolute?
The path of the serial locations of the instantaneous AOR
How do you determine the Instantaneous AOR?
Draw a line between point a (original location) and a' (new location of same point of bone), and then draw a line between b (original location) and b' (new location). Second, draw a perpendicular, and where they intersect is the AOR for that motion
What are the classifications of synovial joints in order from least to most mobile?
Hinge Joint (ulnohumeral)
Ball and Socket Joint: glenohumeral
What are the two classifications of joints by articular shape?
Ovoid surfaces: joints in which one surface is convex and the opposite partner is concave
Sellar surfaces: those in which each partner has both a concave and convex surface (horse's saddle)
What is osteokinematics?
Classical Physiological Movement
Observations you make with your eyes
Examines motion of the body segments around a joint rather than within the joint
What are the two forms of osteokinematics?
Active Joint Movement: Actively performed by a voluntary muscular contraction
Passive Joint Movement: Under voluntary control but is produced by an external force (abduct someone's arm)
What is the importance of the osteokinematics between Tibial-on-femoral and Femoral-on-tibial movements?
Even though the distal segment in tibial-on-femoral movements is free, and the proximal segment in femoral-on-tibial movements is free, they are classified the same because the motion is the same
What is arthrokinematics?
AKA - Accessory movement (subtle movements)
Examines details of movement within a joint rather than the gross movement of the body segments
The joint movement that is produced in isolation only by applying an external force (translating someones humerus caudally, you are the force)
Why are accessory motions important?
If they are not present, an individual is not able to perform ROM normally and pain-free
What are the two types of accessory movements?
What are component motions?
Subtle movements that occur in conjunction with classic physiological motion
Usually cannot be or are not isolated without applying an external force
E.x. when fully extended, finger nails are on the same plane as the palm, but when fully flexed, they are not because of the rotational aspect
What is joint play?
Motions that do not usually occur as part of or in conjunction with classic physiological motions
Usually demonstrable only through use of an external force
E.x. distraction of the proximal phalanx from the metacarpal head by applying traction (determines laxity, can pull humerus from glenohumeral joint; if there is not enough laxity, you must improve that)
How does the knee function to ensure that the tibial plateau and femoral condyles stay in contact with each other?
The joint combines roll and slide
What takes place in a fixed concave mobile convex movement?
As the lateral portion goes up, the medial (convex) portion goes downward
E.x. for someone who has limited abduction, you wold want to move the articular surface caudally to restore normal length of restraining tissues
What takes place in a mobile concave fixed convex motion?
The distal tibia is moving upwards, the articular surface is also moving in the same direction (both sides are on the same side of the AOR)
E.x. Therapeutic force moves the tibia from the posterior to the anterior portion, and this gliding helps restore normal arthrokinematics
What are the two types of joint positions?
Least Packed Position
Closed Packed Position
What is the Least Packed Position?
Composite periarticular tissues are under as minimal and equal tension as possible
Allows maximum joint volume (joint play) because of the slack around the joint
Joint tension is pretty evenly distributed
What is the Closed Packed Position?
Usually the first therapeutic modality for PT
Causes a large portion of the mating surfaces to be congruent (tight)
Tightens the ligaments and capsule
A position of high stability
To force further movement in the direction of tightening will result in tearing or fracture
After a joint injury of swelling, most patients will come in in the close packed position (sling, brace, injured puppy position
What factors impact available motion and joint stability?
Size and Amount of Congruency
What is the relationship between congruency and stability?
High congruency = high stability
What is the kinetic/kinematic chain?
A series of rigid segments linked by movable joints
What is an open kinematic chain?
A kinetic chain in which the distal segment is not "fixed" and is free to move
Movement at any one joint in the chain does not demand movement at any other joint in the chain
What is a closed kinematic chain?
A kinematic chain in which the segments at both ends of the chain are fixed to a surface
Movement at any one joint will demand movement of at least one other joint in the chain
E.x. calf raises: there is not just movement at the ankle, but also the hip
Explain the relationship between normal force and Fsmax in closed chain activities.
As normal force increases, Fsmax increases, because it reduces the net shearing force because of the increased compression force
Why are closed chain exercises beneficial?
They are a closer simulation of physiological activity therefore it improves motor learning and carryover to "normal" activity (probably not true for normal walk [60% of walking cycle in closed chain, 40% in open chain])
Why is it hard to classify swimming as either closed or open chain?
It has parts of open and closed chain aspects
What is the main structure of individual muscle fibers?
Multiple Nuclei and filaments
Myofibrils consist of sarcomeres
Sarcomeres contain myofilaments (myosin and actin)
What is the sliding filament theory?
Contraction results from cross-bridges forming between the actin and myosin molecules (power stroke)
Initiated by impulses from the motor neuron
What are the 3 layers of CT in a muscle belly?
Epimysium - surround the whole muscle
Perimysium - surround the muscle fascicles
Endomysium - surround the individual fibers
What factors influence a muscle's ability to produce a motion?
Architecture of skeletal muscle
Muscle fiber length
Muscle lever arm on joint excursion
What are the different types of muscle fiber orientation?
Are certain muscle fibers longer than others?
In muscles of similar length, pennate muscles contain shorter muscle fibers than parallel fiber muscles
Some of the longest muscle fibers are located in the sartorius
What is the shortening ability of sarcomeres?
~60% of its length
Can myofibrils with more or less fibers shorten more?
Do muscles composed of parallel fibers or pennated fibers have larger shortening capacity?
What is the angle of application?
The angle formed by the line of pull of the muscle and the long axis of the limb (lever) to which the muscle is attached
What is the relationship between angular excursion and lever arm?
Contraction of a muscle with a shorter lever arm produces a larger angular excursion than the same contraction in a muscle with a longer lever arm
What is the relationship between number of fibers and max contraction force?
The more fibers the larger its maximum contraction force
Which fibers have a greater Physiological Cross-Sectional Area (PCSA)?
What factor impacts PCSA?
Changes in activity level over time
What is the length-tension relationship?
A muscle generates a small amount of force when in a shortened position
Explain how force changes as sarcomere length changes.
Force increases linearly as sarcomere length increases, until a little before the resting length, and then the slope increases at a slightly decreased amount. It continues to increases until a little bit after the resting length, and then linearly decreases as the length increases
E.x. For the brachialis,, having the elbow flexed just above 90* is the resting length; leads to optimum actin-myosin interaction
What all does a muscle's response to a stretch depend on?
The sarcomeres and the elastic properties of the connective tissue within the muscle
What is the series elastic element?
The tendon is in series with the muscles
The Series EC springs are actin and myosin
The Parallel EC springs are the CT surround the muscle
Why is the contract-relax stretch method beneficial when it comes to series elastic elements?
If you elongate the muscle to a certain point, all 3 of the springs (parallel and series) will become elongated
What is active insufficiency?
A muscle is so short, that it cannot generate enough contractile force to pull the limb through its full available motion
What is passive insufficiency?
Occurs when a muscle is stretched so that it generates a passive tendon balance between the tension in the muscle and external applied force
What is the relationship between muscle lever arm and force production?
The longer the muscle's lever arm, the greater the torque the muscle produces with its contraction
When a muscle is in its lengthened position, its angle of application (and hence its lever arm) is close to zero
What is the max angle for a muscle's lever arm?
Angle of application of 90*
What are the two classifications of muscles when it comes to the force production and lever arm relationship?
Spurt Muscles and Shunt Muscles
What are spurt muscles?
Primary role is to produce movement; the force vector is causing a rotation in a joint segment
E.x. Biceps brachii
What are shunt muscles?
Primary role is to produce stabilization; the force vector is causing a compression at a joint
What are the different types of muscle contractions?
Concentric: muscle shortens and the joint moves through a ROM; torque changes throughout the rage of motion because of changing moment arms
Isometric: tension develops within the muscle; no movement of the joint occurs
Eccentric: tension develops within the muscle; muscle force is overcome by resistance; muscle lengthens
Isoinertial: don't use this anymore; resistance to motion is controlled; resistance is the same throughout the ROM; produces concentric and isometric contractions
Isokinetic: a shortening contraction; resistance to contraction varies; velocity of movement is constant; special type of concentric contraction
What are the 3 classifications of muscles by their actions?
Agonists (prime movers): a primary muscle which produces the desired movement at a joint
Antagonist: a muscle that may resist the action of the agonist muscle
Synergist: a muscle that works in concert with the prime mover; may prevent an unwanted motion of the prime mover, may act as a helper muscle, or may stabilize another joint to allow the action of the prime mover to occur
What is an example of a movement and the agonist, antagonist, and synergist muscles that go along with it?
Abduction of the arm:
Synergist: abductors on the other side (control COM for stability)
What is the relationship between muscle velocity and muscle concentric contraction force?
The speed of concentric contractions is inversely proportional to the force of the contractions
What is the difference between a twitch and a paired twitch?
Twitch: a single muscle fiber contraction, adequate relaxation, equal force for each stimulation
Paired Twitch: no adequate relaxation period, twitches summate to create a larger twitch
What is the difference between unfused and fused tetanus?
Unfused: series of summated twitches, relaxation period is still inadequate, but present
Fused: no relaxation period, twitches fuse into a single produced force, the highest force output for a muscle fiber
How do age and gender impact force generating capacity?
Age: strength peaks between age 20 ad 30
Gender: strength of females equals males until puberty; greater gain in muscle mass by males afterward; male/female strength per cross-sectional area is approximately the same
What is the function of muscle spindles?
Control the involuntary contraction of skeletal muscle (resting tone, stretch reflex)
What is the function of the sensory portion (afferent) of a muscle spindle?
Sensory portion: Stretch receptors on nuclear bag (and chain) with primary (group 1a neurons) and secondary (group II neurons) that synapse on alpha motor neurons or interneurons to elicit either direct or indirect responses
What is the function of the motor portion (efferent) of a muscle spindle?
Gamma motor neurons to intrafusal muscle fibers. Adjust the sensitivity by controlling resting tension of nuclear bag (and chain) organs
What is the function of Golgi Tendon Organs?
To monitor tension in skeletal muscle tendons and to inhibit muscle contraction before plastic deformation or failure of tendon occurs
What is the function of the sensory portion (afferent) of golgi tendon organs?
Golgi tendon organ (stretch receptor) with Group 1b nerve fiber. Synapse on interneurons which have an inhibitory effect on alpha motor neurons
What is the function of the motor portion (efferent) of golgi tendon organs?
Golgi tendon organs have no motor portions
Where are sensory receptors located? And what is their function?
They exist within and around joints, which plays a role in position sense (static) and kinesthesia (movement angle, velocity, acceleration)
Where are joint receptors found?
Fibrous portions of the joint capsule, capsular ligaments, intra articular ligaments, ligaments at a distance and at the attachments of menisci
Receptors are also found at the outermost periphery of IV discs, the pubic symphysis, the synarthroidial portion of the SI joints, and periosteum
No receptors involved with the synovial lining or in the articular cartilage
What is Hilton's law?
If a muscle crosses a joint, the nerve supplying that muscle also sends a sensory branch of the joint
What are Golgi-Mazzoni Corpuscles?
What are Pacinian Corpuscles?
What are Golgi Ligament Endings?
What are Free Nerve Endings?
What are the neurological effects of high load, short duration strength training?
Increased synchrony of agonist motor unit firing
Increased number of motor units firing (Untrained = 60% activation; Trained = 90% activation)
Decrease antagonist muscle firing
What are the effects of low load, long duration endurance training?
Muscle adaptation through increased oxidative enzymes through increased mitochondria size, number, and density
Cardiovascular adaptation through central changes by increasing SV of heart with larger ventricular size and peripheral changes by increasing number of capillaries within muscle especially around type I fibers
Metabolic adaptations shift from glycogen to fatty acid utilization for energy
What are the effects of increased resting length on muscle biology?
Immediate response is to "pull apart" existing actin and myosin (muscle is weaker)
Remodeling occurs over several weeks
Sarcomeres added to ends of existing muscle cells
Myotendinous junction is most active for addition of sarcomeres
Causes relative increase in force generation capacity due to contractile elements (more contractile proteins per cell)
Intramuscular connective tissue remodeling occurs to elongate passive elements
What is the effects of decreased resting length on muscle biology?
Immediate response is to overlap existing actin and myosin (muscle is weaker)
Remodeling occurs over several weeks
Sarcomeres removed at ends of muscle cell
Relative decrease in force generation capacity due to contractile elements (fewer contractile proteins per cell
Intramuscular connective tissue remodeling occurs to shorten passive elements
What are the effects of muscle atrophy on muscle biology?
Exponential loss of muscle weight
Greatest percent loss of mass is within the first 3-5 days
Antigravity muscles demonstrate the greatest loss
What are the effects of loss of force generating capacity on muscle biology?
Loss of diameter of individual fibers (both type I and Type II)
Decreased cross-sectional area
What are the effects of increased fatiguability on muscle biology?
Diminished biochemical capacity to resist fatigue
What other changes that might be observed effect muscle biology?
Diminished muscle protein synthesis (within hours)
Changes in motor end plate and muscle-nerve interaction (within hours to days)
Altered proprioceptive input to CNS
Changes in motor unit synchrony
Changes in joint stiffness