CHAPTER 2:MUSCULOSKELETAL SYSTEM:
FRAMEWORK AND MOVEMENTS
KINESIOLOGYScientific Basis of Human Motion, 12th edition
Hamilton, Weimar & LuttgensPresentation Created by
TK Koesterer, Ph.D., ATCHumboldt State University
Revised by Hamilton & Weimar
Copyright © 2012 by The McGraw-Hill Companies, Inc. All rights reserved.McGraw-Hill/Irwin
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MUSCULOSKELETAL FRAMEWORK
An arrangement of bones, joints, and muscles.
Acts as a lever system allowing for a great number of coordinated movements.
An anatomical lever is a bone that engages in movement when force is applied to it.
The force is from a muscle attached to the bone or an external force (gravity or weight).
Muscles can produce motion only by shortening.
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THE BONES
Skeleton: provides support, muscle attachment, & protection
Axial: skull, spinal column, sternum, and ribs
Appendicular: upper and lower extremities
Fig 2.1
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THE BONES: SKELETAL CHANGES
Growth Osteogenesis Initial matrix Osteoblasts form bone on matrix. Bone forms in response to loading stress.
Degeneration Osteoclasts reabsorb bone in the absence of stress. Bones become more porous and brittle; osteoporosis.
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THE BONES:
Bone typesTwo types allow bone to
be strong, yet light.Compact: dense outer
boneCancellous: open,
spongy looking inner bone
Fig. 2.2
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TYPES OF BONES
Long: shaft or body with a medullary canal, and relatively broad, knobby ends Femur, tibia, humerus, ulna, radius, etc.
Short: relatively small, chunky, solid Carpals and tarsals
Flat: flat & plate like Sternum, scapulae, ribs, pelvis
Irregular: bones of spinal column Vertebrae, sacrum, & coccyx
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MECHANICAL AXIS OF A BONE
A straight line that connects the midpoint of the joint at one end of a bone with the midpoint of the joint at the other end.
The axis may lie outside the shaft.
Fig 2.3
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SKELETAL CHANGES
Epiphysis is a part of a bone separated from the main bone by a layer of cartilage.
Epiphyseal cartilage is where growth occurs. When this cartilage ossifies and closure is
complete, no more growth can occur. Tables 2.1 & 2.2: ages of ossification Need to be aware of epiphyseal injuries in children
& adolescents.
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ARTICULATIONS
Structure and function of joints are so interrelated that it is difficult to discuss them separately.
The configuration of the bones that form an articulation, together with the reinforcing ligaments, determine and limit the movements of the joint.
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STRUCTURAL CLASSIFICATION
Based on presence or absence of a joint cavity:Diarthrosis or Synarthrosis
Further classified either by shape or nature of the tissues that connect the bones.
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DIARTHROSIS: CHARACTERISTICS
Articular cavity Ligamentous
capsule Synovial membrane Surfaces are
smooth Surfaces covered
with cartilage Fig 2.5
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DIARTHROSIS: CLASSIFICATION Irregular joint: irregular surfaces, flat or slightly curved,
permits gliding movement. Hinge joint: convex/concave surfaces, uniaxial, permits
flexion/extension. Pivot joint: a peg-like pivot, permits rotation. Condyloid joint: oval or egg-shape convex surface fits into a
reciprocal concave surface, biaxial, permits flexion/extension, ab & adduction, and circumduction.
Saddle: modification of condyloid, both surfaces are convex and concave, biaxial, permits flexion/extension, ab & adduction, and circumduction.
Ball-and-socket: head of one bone fits into the cup of the other bone.
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TYPE OF JOINTS
Plane Hinge Pivot CondyloidIntercarpal Elbow Atlantoaxial Radiocarpal
Condyloid Saddle Ball & Socket Ball & SocketMCP joint Thumb Shoulder Hip
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SYNARTHROSIS: CHARACTERISTICS
No articular cavity, no capsule, synovial membrane or synovial fluid.
In two types, bones are united by cartilage or fibrous tissue.
Third type, not a true joint, but is a ligamentous connection between bones.
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SYNARTHROSIS: CLASSIFICATION
Cartilaginous joint: united by fibrocartilage permits bending & twisting motions.
Fibrous joint: edges of bone are united by a thin layer of fibrous tissue, no movement permitted.
Ligamentous joints: two bodies are tied together by ligaments, permits limited movement of no specific type.
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JOINT STABILITY Function of joints is to provide a means of moving or, rather, of being
moved. Secondary functions is to provide stability without interfering with the
desired motions. All joints do not have the same degree of stability.
Emerson’s law: “For everything that is given, something is taken”. Movement is gained at the expense of stability.
Resistance to displacement Factors responsible for stability
Bony structure Ligamentous arrangement Muscle tension Fascia Atmospheric pressure
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SHAPE OF BONY STRUCTURE
May refer to kind of joint:Hinge, condyloid, pivot, or ball-and-socket
Or specific characteristics of a joint:Depth of socket
More stable, less mobile
More mobile, less stable
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LIGAMENTOUS ARRANGEMENTS
Ligaments are strong, flexible, stress-resistant, somewhat elastic, fibrous tissues that form bands or cords.
Join bone to bone. Help maintain relationship of bones. Check movement at normal limits of joint. Resist movements for which joint is not
constructed. Will stretch when subject to prolonged
stress. Once stretched, their function is affected.
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MUSCULAR ARRANGEMENT
Muscles that span joints aid in stability.
Especially when bony structure contributes little to stability.
Fig 5.13
Muscles acting to stabilize the shoulder
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FASCIA AND SKIN
Fascia consists of fibrous connective tissue. May form thin membranes or tough, fibrous
sheets. Intense or prolonged stress may cause
permanent stretch. Iliotibial tract and thick skin covering the knee
joint are examples.
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ATMOSPHERIC PRESSURE
Negative pressure in joint capsule forms a vacuum.
The suction created is an important factor in resisting dislocation of a joint.
Key in hip and shoulder joints.
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FACTORS AFFECTING THE RANGE OF MOTION (ROM) Three factors that affect the stability of a joint are
also related to its ROM:1. Shape of articular surfaces.2. Restraining effect of ligaments.3. Muscles and tendons (single most important
factor). Flexibility should not exceed muscle’s ability to
maintain integrity of joint. Additional factors include: injury or disease,
gender, body build, heredity, occupation, exercise, and age.
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METHODS OF ASSESSING A JOINT’S RANGE OF MOTION
Measure degrees from starting position to its maximal movement.
Goniometer: axis placed directly over center of joint, one arm held stationary, other arm held to moving segment.
Fig 2.7
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METHODS OF ASSESSING A JOINT’S RANGE OF MOTION
Videotape: joint centers are marked to be visible in projected image.
Joint angles can be taken from images.
Segment action must occur in picture plane.
Fig 2.8 85°
91°
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AVERAGE RANGES OF JOINT MOTION
Ranges vary and it is difficult to establish norms.
Age, gender, body build, and level of activity may all be factors.
Four sets of ranges are presented in table 2.4.
Illustration of joint ROM for most fundamental movements are found in Appendix B.
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ORIENTATION OF THE BODY
Center of Gravity: imaginary point representing the weight center of an object
Line of Gravity: imaginary vertical line that passes through the center of gravity
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ORIENTATION OF THE BODYPLANES OF THE BODY
Fig2.8
Sagittal Frontal Transverse
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ORIENTATION OF THE BODYAXES OF MOTION
Bilateral: axis passes horizontally from side to side; perpendicular to sagittal plane.
Anteroposterior or AP: axis passes horizontally from front to back; perpendicular to frontal plane.
Vertical: axis is perpendicular to the ground and transverse plane.
Rotation occurs in a plane and around an axis. Axis of movement is always at right angles to the
plane in which it occurs.
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ORIENTATION OF THE BODYSTANDARD STARTING POSITIONS
Fig 2.10
Fundamental Standing Position
Anatomical Standing Position
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FUNDAMENTAL MOVEMENTS SAGITTAL PLANE ABOUT A BILATERAL AXISFlexion: reduction in joint angle. Examples:
Tipping the head forward Lifting the foot & leg backward from knee Raising entire lower extremity forward-
upward as though kicking Raising forearm straight forward Elbow straight, raising entire upper extremity
forward-upward
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FUNDAMENTAL MOVEMENTS SAGITTAL PLANE ABOUT A BILATERAL AXIS
Extension: return movement from flexion.Hyperflexion: arm is flexed beyond vertical.Hyperextension: continuation of extension
beyond starting position.Reduction of Hyperextension: return
movement from hyperextension.
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JOINT MOTIONS IN THE SAGITTAL PLANE AROUND A BILATERAL AXIS.
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FUNDAMENTAL MOVEMENTS FRONTAL PLANE ABOUT AN AP AXIS
Abduction: movement away from the midline.Adduction: return movement from abduction.Lateral Flexion: lateral bending of head or trunk.Hyperabduction: arm abducted beyond vertical.Hyperadduction: move across in front of the body.Reduction of Hyperadduction: return movement.Reduction of Lateral Flexion: return movement.
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JOINT MOTIONS IN THE FRONTAL PLANE AROUND AN ANTERO-POSTERIOR AXIS.
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FUNDAMENTAL MOVEMENTS TRANSVERSE PLANE ABOUT A VERTICAL AXIS(Point of reference for the upper extremities is the
midpoint of the fundamental (not anatomic) position.)
Rotation Left & Right: rotation of head, neck, or pelvis.
Lateral & Medial Rotation: rotation of thigh and upper arm.
Supination & Pronation: rotation of forearm along long axis.
Reduction of Lateral Rotation, Medial Rotation, Supination, or Pronation: rotation of segment back to mid-position.
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TORSO MOTION IN THE TRANSVERSE PLANE AROUND A VERTICAL AXIS.
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FUNDAMENTAL MOVEMENTS COMBINATION OF PLANES
Circumduction: whole segment describes a cone. arm circling and trunk circling
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NAMING JOINT ACTION IN COMPLEX MOVEMENTS All joint actions are named as if they were
occurring in anatomical position. The plane and axis are identified as those
in which the movement actually occurs.Non-axial MovementsMovements in plane joints are non-axial
gliding movements between articular facets of spinal column.
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ANALYZING JOINT MOTIONS
Alignment: optimum alignment should be based on efficiency, effectiveness, and safety.
Range of Motion: ROM demands of an activity must be compatible to avoid injury.
Flexibility: reduces internal resistance to motion.
