Chapter 2: The Musculoskeletal System: The Skeletal Framework and Its Movements

Outline

• The Bones

  Skeletal Changes

  Types of Bones

  Mechanical Axis of a Bone

• Articulations

  Structural Classification

  Suggestions for Studying Joint Structure

  Joint Stability

  Factors Affecting the Range of Motion

  Methods of Assessing a Joint's Range of Motion

  Average Ranges of Joint Motion

• Orientation of the Body

  The Center of Gravity

  The Line of Gravity

  Orientation Planes of the Body and Axes of Motion

  Standard Starting Positions

• Fundamental Movements of the Major Body Segments

  Movements in the Sagittal Plane about a Bilateral Axis

  Movements in the Frontal Plane about an Anteroposterior Axis

  Movements in the Transverse Plane about a Vertical Axis

  Movements in a Combination of Planes

  Naming Joint Actions in Complex Movements

  Nonaxial Movements

• Analyzing Joint Motions

• Laboratory Experiences

Objectives

At the conclusion of this chapter, the student should be able to:

1. Classify joints according to structure and explain the relationship between a joint structure and its capacity for movement.

2. Explain how the schedule of ossification of epiphyseal cartilage is related to the nature of activities suitable for different age groups.

3. Name the factors that contribute to joint range of motion and stability and explain the relationship that exists between range of motion and stability.

4. Assess a joint's range of motion, evaluate the range, and describe desirable procedures for changing it when indicated.

5. Name and define the orientation positions and planes of the body and the axes of motion.

6. Demonstrate and name fundamental movement patterns using correct movement terminology.

7. Isolate and name single joint actions that are part of complex movements.

8. Perform an anatomical analysis of the joint actions and planes of motion for a selected motor skill.

It is customary—especially for students of human movement and exercise—to begin the study of anatomy with a detailed study of the bones, then to proceed to the joints, and then to the muscles. This path of investigation sometimes dampens the enthusiasm of students, whose chief focus of interest is movement. Therefore, this chapter and the next emphasize the concept of the total musculoskeletal system as a mechanism for motion. It is hoped that by using this concept the student will find the study of the structural elements of this system more meaningful.

As the phrase implies, the musculoskeletal framework is an arrangement of bones and muscles. Adjacent bones are attached to one another by joints, which provide for the motion of the articulating bones, and the muscles that span the joints provide the force for moving the bones to which they are attached. Mechanically, the total bone–joint–muscle structure is an intricate combination of levers that makes possible a great number of coordinated movements, ranging from the small hand and finger motions used in assembling a television set or playing the piano to the total body movements of a swimmer or a pole vaulter. Any single one of the levers involved in such movements is relatively simple.