Foundations of Biomechanics I: Kinematics

Question 1

Kinesiology

Answer 1

• study of motion

- requires knowledge of: anatomy, physiology, neurology, physics, growth and development

Question 2

Biomechanics

Answer 2

• an area within kinesiology
• apply mechanics to human body
• study mechanics of life
• science that examines internal and external forces acting on a body and the effects produced by these forces

Question 3

Scalar Quantities

Answer 3

• has magnitude but no direction
• specified by a single number
• many quantities in biomechanics may become completely specified by their magnitudes
• ex: mass, volume, time, length, speed, shoe size, temp
• obey ordinary laws of addition, subtraction, multiplication, and division

Question 4

Vector Quantities

Answer 4

• has magnitude and direction
• characterized by: a point of application, direction and line of action, quantity or magnitude
• often symbolized with arrows
• ex: velocity, acceleration, muscular force, gravity, friction
• obey ordinary laws of addition, subtraction, multiplication, division

Question 5

Kinematics

Answer 5

• science –> description of motion
• no concern re: forces causing motion
• describes: type of motion, direction of motion, quantity of motion, location of motion
• clinical examples: goniometer, videotape, stop watch, PTs knee flexed to 90 degrees

Question 6

Kinetics

Answer 6

• science –> effect of forces
• concern with forces that stop, cause, or change motion
• describes: magnitude of force, direction of force, type of force, location of force
• clinical examples: dynamometers, force plates, MMT, cybex

Question 7

Linear Motion

Answer 7

• aka rectilinear motion
• object moves along linear path
• all of object’s parts travel: exactly the same distance, in the same direction, at the same time
• individual points move at equal velocities
• ex: person in w/c, sled going downhill, head receiving Tx

Question 8

Rotary Motion

Answer 8

• object moves along circular path
• all object’s parts travel: through same arc, in the same direction, at same time
• movement occurs about an axis
• axis may be external or internal to body
• individual points move at different velocities
• ex: bending at elbow, raising a tilt table, marching band turning a circle

Question 9

Coupled Motions

Answer 9

• aka general motion
• combination of linear, rotary, or curvilinear motions
• ex: lungs, riding bike, lower extremity during gait
• most human motion

Question 10

Describing Joint Function: Kinematic Chains

Answer 10

• combo of several joints utilizing several segments
• an attempt to describe collective joint actions
• can exert way more force with closed kinematic chain than with open

Question 11

Open Kinematic Chain

Answer 11

• distal segment moves freely in space
• movement of distal segment is less predictable
• ex: waving goodbye, follow through on jump shot, swing phase of gait

Question 12

Closed Kinematic Chain

Answer 12

• distal segment is fixed
• movement of all joints fairly predictable
• motion at one joint influences motion at another joint(s)
• ex: pushups, stance phase of gait, opening a door

Question 13

Osteokinematics

Answer 13

• describes gross movement of bones
• what we see
• aka anatomic or physiological ROM
• measured clinically with goniometer or inclinometer

Question 14

Arthrokinematics

Answer 14

• study of movements of joint surfaces during joint motion
• define motion not by action of long axis but by joint surface
• describing the hinge instead of the door
• aka non-physiologic or accessory motion
• what’s happening internally

Question 15

Arthrokinematic Terminology: Roll

Answer 15

• each point on moving joint surface contacts a new point on other surface
• i.e. tire rolling down road
• occurs in the direction of the swing of the bone

Question 16

Arthrokinematic Terminology: Slide

Answer 16

• one point on moving joint surface contacts new poins on other surface
• i.e. tire sliding on ice
• direction of slide determined by the shapes of joint surfaces

Question 17

Concave-Convex Rule

Answer 17

• slide and roll occur in the same direction
• slide occurs in same direction of long bone segment
• ex: tibia extending on a stabilized femur, proximal phalanx moving on metacarpal

Question 18

Concave-Convex Rule

Answer 18

• slide and roll occur in opposite directions
• slide occurs in opposite direction of long bone segment
• ex: femur extending on stationary tibia, metacarpal moving on phalanx

Question 19

Close-Pack Position

Answer 19

• joint surfaces are matched perfectly or are congruent
• maximum area of surface contact between joint surfaces
• ligaments and capsule taut
• cannot be distracted
• ex: extended tib-fib joint, extended humeroulnar joint, extended interphalangeal joint

Question 20

Loose-Pack Position

Answer 20

• all other positions
• joint surfaces not perfectly matched
• ligaments and capsule slack
• joint surfaces can be distracted
• ex: flexed tib-fib joint, flexed humeroulnar joint, flexed IP joint

Question 21

Arthrokinematics in Knee

Answer 21

• tibiofemoral joint
• patellofemoral joint
• close pack position and loose pack position are different for these joints

Question 22

Take Home Messages

Answer 22

• physical therapists use kinematics daily to describe the types of motion they see clinically
• scalar and vector quantities have different characteristics and tell us different things
• human movement is comprised of linear, rotary, and coupled types of motion, and these motions can often occur simultaneously
• osteokinematics and arthrokinematics describe the motion of skeletal system in very different ways