Chapter 3
Kinesiology of the musculoskeletal
system
Overview
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A fundamental skill of the physical
therapist is to identify, analyze and
solve problems related to human
movement
Anatomical reference
point
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When describing movements it is necessary
to have a starting position as the reference
position. This starting position is referred to
as the anatomical reference position.
The anatomical reference position for the
human body is described as the erect
standing position with the feet just slightly
separated and the arms hanging by the
side, the elbows straight and with the palms
of the hand facing forward
Directional Terms
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Superior or cranial – Closer to the head
Inferior or caudal – Closer to the feet
Anterior or ventral – Toward the front of the
body
Posterior or dorsal – Toward the back of the
body
Medial – Toward the midline of the body
Lateral – Away from the midline of the body
Directional Terms
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Proximal – Closer to the trunk
Distal – Away from the trunk
Superficial – Toward the surface of the
body
Deep – Away from the surface of the
body in the direction of the inside of
the body
Planes of the Body
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There are three traditional planes of the body
corresponding to the three dimensions of space:
sagittal, frontal, and transverse
Sagittal plane. Also known as the anterior-posterior
or median plane. Divides the body vertically into
left and right halves of equal size
Frontal plane. Also known as the lateral or coronal
plane. Divides the body equally into front and back
halves
Transverse plane. Also known as the horizontal
plane. Divides the body equally into top and bottom
halves
The Center and Line of
Gravity
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The center of gravity may be defined
as ‘the point at which the three planes
of the body intersect each other’
The line of gravity is defined as ‘the
vertical line at which the two vertical
planes intersect each other’
Axes of the Body
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Three reference axes are used to
describe human motion: frontal,
sagittal, and longitudinal. The axis
around which the movement takes
place is always perpendicular to the
plane in which it occurs.
Axes of the Body
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Frontal. The frontal axis, also known
as the transverse axis, is perpendicular
to the sagittal plane
Sagittal. The sagittal axis is
perpendicular to the frontal plane
Longitudinal. The longitudinal axis,
also known as the vertical axis is
perpendicular to the transverse plane
The planes and axes for
common movements
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Flexion, extension, hyperextension,
dorsiflexion, and plantar flexion occur in the
sagittal plane around a frontal-horizontal
axis
Abduction, adduction; side flexion of the
trunk; elevation and depression of the
shoulder girdle; radial and ulnar deviation of
the wrist; eversion and inversion of the foot
occur in the frontal plane around a sagittalhorizontal axis
The planes and axes for
common movements
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Rotation of the head, neck and trunk;
internal rotation and external rotation of the
arm or leg; horizontal adduction and
abduction of the arm or thigh; pronation
and supination of the forearm occur in the
transverse plane around the longitudinal
axis
Circumduction involves an orderly sequence
of circular movements that occur in the
sagittal, frontal and intermediate oblique
planes, so that segment as a whole
incorporates a combination of flexion,
extension, abduction and adduction
Kinematics
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Kinematics is the study of motion. In
studying joint kinematics, two major
types of motion are involved:
– The osteokinematic
– The arthrokinematic
Osteokinematic Motion
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Osteokinematic motion occurs when
any object forms the radius of an
imaginary circle about a fixed point
The axis of rotation for osteokinematic
motions is oriented perpendicular to
the plane in which the rotation occurs
Osteokinematic motion
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Examples of osteokinematic motion
include abduction or adduction of the
arm, flexion of the hip or knee, and
side flexion of the trunk
Arthrokinematic Motion
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Arthrokinematic movements are the
motions occurring at the joint surfaces
Direction of movement based on the
shape of the joint surfaces
Generally, joint surfaces can be either
concave (female) or convex (male) in
shape (ovoid), or a combination of
both shapes (sellar)
Arthrokinematic Motion
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The three types of movement occur at
the articulating surfaces:
– Roll
– Slide
– Spin
Motion relationships
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Osteokinematic and arthrokinematic
motions are directly proportional to
each other and one cannot occur
completely without the other
Thus, if motion is reduced, one, or
both, of these motions is at fault
Degrees of Freedom
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The number of independent modes of
motion at a joint is called the degrees of
freedom (DOF)
– A joint that can swing in one direction or can
only spin, it is said to have 1 DOF. Example: PIP
joint
– A joint that can spin and swing in one way only
or it can swing in two completely distinct ways,
but not spin, it is said to have 2 DOF. Example:
Tibiofemoral joint
Degrees of Freedom
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If the joint can spin and also swing in
two distinct directions then it is said to
have 3 DOF . Example: Glenohumeral
joint
Conjunct Rotation
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The rotation at a joint that
accompanies the prime motion.
Example: supination of the forearm
during elbow extension
Conjunct rotation is only under
volitional control in joints with 3 DOF
Conjunct rotation
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Where appropriate, mobilizing
techniques must take into
consideration both the relative shapes
of the articulating surfaces, in addition
to the conjunct rotation that is
associated with a particular motion
Kinematic chains
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The expression kinematic chain is used
in rehabilitation to describe the
function or activity of an extremity or
trunk in terms of a series of linked
chains
Kinematic chains
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Closed kinematic chain
– Various definitions
– Fixation of the distal segment so that
joint motion takes place in multiple
planes and the limb is supporting weight
Kinematic chains
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Open kinematic chain
– All activities that involve the end segment
of an extremity moving freely through
space
Close-packed Position
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The position of maximum congruity of
the opposing joint surfaces is termed
the close-packed position of the joint
Movements toward the close-packed
position of a joint involve an element
of joint compression
Position of maximum joint stability
Open-packed Position
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The position of least joint congruity is
termed the open-packed position
Movements away from the closepacked position involve an element of
joint distraction
Position of least joint stability
Available Joint Motion
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If a joint moves less than what is
considered normal, or when compared to
the same joint on the opposite extremity, it
may be deemed hypomobile
A joint that moves more than considered
normal, or when compared to the same
joint on the opposite extremity, may be
deemed hypermobile.
Available Joint Motion
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Instability of a joint involves a
disruption of the osseous and
ligamentous structures of that joint,
resulting in a loss of function
Factor of joint integrity, elastic energy,
passive stiffness, and muscle
activation