Biomechanics Pt. 1 (8/30a) Flashcards
Biomechanics
Uses principles of engineering to model human movement
“The study of structure and function of biological systems by the means of the methods of mechanics” (Herbert Hatze 1974)
Kinematics
refers to the description of motion of a body without reference to the forces that caused the motion of the body
AKA describes motion only
Translational/linear motion
all points on rigid body in the same direction and same distance
EX: displacement of the body’s center of mass (approximately just anterior to sacrum in pelvis)
Rotational/angular motion
all points on rigid body move in circular path around pivot point
Axis of rotation
point that remains stationary or pivot point for angular motion
Linear kinematic measures
displacement (meters)
velocity (meters/second)
acceleration (meters/sec2)
Rotational kinematic measures
angular displacement (degrees)
velocity (degrees/second)
acceleration (degrees/sec2)
Do joints in the human body rotate, translate, or both?
Both
Center of mass (COM)
the balance point within a body, the point where gravity is assumed to act (center of gravity)
Center of gravity (COG)
point at which the weight of an object is concentrated
Depends on shape and mass distribution; position dependent
Active motion
any conscious or subconscious movement you do on your own
EX: lifting your knee, blinking, running, etc
Passive motion
movement that an external force physically makes you do
EX: a PT moving your knee into flexion to check ROM
Osteokinematics
Describes motion of a bone relative to cardinal plane of motion
angular motion
Frontal/coronal plane
PLANE: frontal/coronal
MOVEMENT: abduction/adduction
AXIS: anterior/posterior axis
Sagittal plane
PLANE: sagittal
MOVEMENT: flexion/extension
AXIS: medial/lateral axis
Horizontal/transverse plane
PLANE: horizontal/transverse
MOVEMENT: external/internal rotation
AXIS: longitudinal/vertical axis
Degrees of freedom (DOF)
number of permitted planes of angular motion at a point
Number of degrees of freedom
3 DOF = 1 for each angular plane
Exceptions to DOF in body
Not all joints allow 3 DOF
Hinge joint - 1 DOF (sagittal)
Pivot joint - 1 DOF (transverse)
Ball & socket joint - 3 DOF (frontal, sagittal, transverse)
Arthrokinematics
Describes motion between joint surfaces
translational motion
Most joints have at least a slightly curved shape, which creates a ____-____ relationship between surfaces
convex-concave
Joint play/Accessory joint motion
Translation motion arises from active muscles and natural laxity/looseness of a joint
DOF with joint play
Linear translational motion + angular motion
3 angular DOF + 3 linear DOF = 6 DOF
3 motions at joint surfaces
Roll
Slide/Glide
Spin
Roll (joint motion)
multiple points along a rotating articular surface contact multiple points on the other articular surface
Slide/glide (joint motion)
a single point on one articular surface contacts multiple points on another articular surface
Spin (joint motion)
a single point on one articular surface rotates on a single point on another articular surface
If you move the CONCAVE surface on the CONVEX surface…
the arthrokinematic motion between the surfaces will occur in the SAME direction as the osteokinematic motion
If you move the CONVEX surface on the CONCAVE surface…
the arthrokinematic motion between the surfaces will occur in the OPPOSITE direction as the osteokinematic motion
Closed packed joint position
best fit or most congruent position
Closed packed ligaments usually taut, motion between joint surfaces is minimal, more contact area, less space in joint
Loose/open packed joint position
resting position
Open packed ligaments are loose, can be a lot of joint play, often mid-range of motion, less contact area, more space in joint
Open packed position can accommodate joint swelling, fluid buildup, injury
CASSS Movement Analysis
Control - how smooth?
Amount - how much?
Speed - how long does it take to do?
Symmetry - is it the same as the other side?
Symptom - does it hurt or is it bothersome?
Which side of the body do you analyze first?
The unimpaired side to create baseline/understand what normal movement is for patient
