1. Kinesiology: The Skeletal System and Muscle Function
Joseph E. Muscolino, DC
Instructor, Purchase College
State University of New York
Owner, The Art and Science of Kinesiology
Stamford, Connecticut
Kinesiology: The Skeletal System and Muscle Function
Second Edition

2. Chapter 5: Joint Action Terminology
Joseph E. Muscolino, DC
● Chapter 5 begins Part III of the textbook. This part of the textbook focuses on skeletal arthrology, the study of the joints. Chapter 5 continues the exploration of motion in the body by addressing the various types of joint motion.

3. Lesson 5.1 Objectives
Define the key terms of this chapter and state the meanings of the word origins of this chapter.
With regard to joint motion, explain the function of joints, muscles, and ligaments/joint capsules.
● The textbook has a list of key terms and word origins for each chapter. Most of these terms will become familiar as the material is covered, but reviewing them, especially the word origins, before reading the chapter can be helpful. Definitions for the key terms are available from the Evolve Website.

4. Lesson 5.1 Objectives (cont’d.)
Describe the characteristics of axial motion.
Describe the characteristics of nonaxial motion.
Describe, compare, and contrast rectilinear and curvilinear motion.

5. Section 5.1—Overview of Joint Function
Joints allow movement.
Muscles create movement.
Ligaments/joint capsules limit movement.
● The primary function of a joint is to allow movement. The word allowing shows that joints are passive.
● The movement that occurs at a joint is created by a muscle. The word created shows that muscles are dynamic.
● Muscles do not necessarily have to create motion; rather, they create forces. Forces can create motion, but they can also modify or stop motion.
● Ligaments and joint capsules function to limit excessive movement at a joint.

6. Section 5.1—Overview of Joint Function (cont’d.)
Additional Characteristics of Joints:
Weight bearing
Shock absorption
Stability
● Weight-bearing joints need to be very stable to support the weight that is borne through them. Most every joint of the lower extremity and all the spinal joints of the axial body are weight-bearing joints.
● Joints can function to absorb shock due to the cushioning effect of the fluid within the joint cavity. This is especially important for weight-bearing joints.
● Mobility and stability are antagonistic properties: A more mobile joint is less stable; a more stable joint is less mobile.

7. Section 5.2—Axial and Nonaxial Motion
● Axial motion is a motion of a body part that occurs about or around an axis. Figure 5-1a shows the scapula upwardly rotating, which is an example of axial motion.
● What is another name for this type of motion?
This type of motion is also called circular motion because the body part moves along a circular path around the axis.
● Nonaxial motion does not occur about or around an axis. Figure 5-1b shows the scapula protracting, which is an example of nonaxial motion.
Figure 5-1

8. Section 5.3—Nonaxial/ Gliding Motion
● Nonaxial motion is also knows as a gliding motion because the bone that moves is said to glide along the other bone of the joint.
● What are some other synonyms for nonaxial motion?
Nonaxial motion is also known as a sliding motion, linear motion, or translation.
● The scapula is protracting in this illustration. The dashed lines represent the identical motion of three separate points along the scapula. The bold line demonstrates the motion of the entire scapula, which is a nonaxial or linear motion.
Figure 5-2

9. Section 5.3—Nonaxial/ Gliding Motion (cont’d.)
● Figure 5-3a shows nonaxial motion of one carpal bone of the wrist along an adjacent carpal bone.
● Figure 5-3b illustrates nonaxial motion of one vertebra along another vertebra at the disc and facet joints of the spine.
Figure 5-3

10. Section 5.4—Rectilinear and Curvilinear Nonaxial Motion
● In the diagram on the left, the skier is gliding along the snow in a straight line. This type of nonaxial linear motion is called rectilinear motion.
● In the figure on the right, the skier’s body is now jumping through the air along a curved path. What type of nonaxial linear motion is this movement called?
It is called curvilinear motion.
Figure 5-4

11. Lesson 5.2 Objectives
Explain the relationship between axial motion and the axis of movement.
Describe roll and spin axial motions.
Explain the relationship of roll, spin, and glide movements.
Be able to state the three components of naming a joint action.

12. Section 5.5—Axial/ Circular Motion
● When moving in a circular path around an axis, not every point on the body part moves an equal amount; points closer to the axis move less than points further from the axis.
● Does every point on the body part move along the circular path through the same angle?
Yes. Every point moves through the same angle in the same direction at the same time as every other point on the body part.
● What are some synonyms for axial motion?
They are circular, angular, and rotary motion.
Figure 5-5

13. Section 5.6—Axial Motion and the Axis of Movement
● What occurs during axial motion?
The body part that is moving moves along a circular path. If we place a point at the center of this circular path, we will have the point around which the body part moves. Every axial movement moves around an axis.
● The axis of movement is the imaginary line around which axial motions occur. In Figure 5-6a, the axis is mediolateral in orientation. In Figure 5-6b, the axis is anteroposterior in orientation. Axes of movement are always perpendicular to the plane in which the motion is occurring.
Figure 5-6

14. Section 5.7—Roll and Spin Axial Movements
● Axial movements can be broadly divided into two categories.
● The first category, called rolling (or rocking) movement, is where the body part changes its position in space and one end of the bone moves more than the other end of the bone. Flexion of the arm at the shoulder joint is an example of this movement, as seen in Figure 5-7a.
● The second category, called spinning (or rotation) movement, is where the body part does not change its position in space; rather it rotates or spins, staying in the same location, as seen in Figure 5-7b (the arm is laterally rotating).
Figure 5-7

15. Section 5.8—Roll, Spin, and Glide Movements Compared
● Roll, glide, and spin are the fundamental component motions that make up all named motions that kinesiology students learn.
● This figure shows the fundamental motions of roll, spin, and glide by showing the convex-shaped bone as moving on the concave-shaped bone. It is also possible for the concave-shaped bone to move along the convex-shaped bone.
● Which of these movements is a linear nonaxial movement?
Figure 5-8c shows the linear nonaxial movement called glide.
Figure 5-8
(Modeled from Neumann DA: Kinesiology of the musculoskeletal system: foundations for physical rehabilitation, St Louis, 2002, Mosby.)

16. Section 5.8—Roll, Spin, and Glide Movements Compared (cont’d.)
Figure 5-9
● An analogy of a car tire helps illustrate the joint motions of roll, spin, and glide.
● The tire rolling along the ground in Figure 5-9a illustrates roll.
● The tire that is spinning without changing location represents spin in Figure 5-9b.
● Figure 5-9c shows the tire that is gliding (sliding or “skidding”) along the ground.

17. Section 5.9—Naming Joint Actions Completely
Three Steps to Describe an Action:
Directional term
Body part
Joint
● The advantage to being more complete in naming joint actions is that it requires us to clearly see exactly what is happening with each action of the body that occurs.
● Most of the commonly thought of actions of the human body are axial movements, and generally the axis of movement is a line that runs through the joint. In describing these movements, we use terms that indicate the direction that the body part has moved. We also name the body part that moves and the joint where motion occurs.

18. Section 5.9—Naming Joint Actions Completely (cont’d.)
● Figure 5-10 illustrates flexion of the right forearm at the elbow joint. Notice the three steps are included: directional term, body part, and joint.
● A bone can be named as doing the moving instead of a body part and is sometimes more advantageous because it is a more specific description. For example, instead of saying that the arm moves, we could say that the humerus moves.
Figure 5-10

19. Lesson 5.3 Objective
Define joint action terms and be able to show examples of each one.

20. Section 5.10—Joint Action Terminology Pairs
Major Pairs of Directional Terms:
Flexion/extension
Abduction/adduction
Right lateral flexion/left lateral flexion
Lateral rotation/medial rotation
Right rotation/left rotation
● These five major pairs of directional terms will be covered in this lesson. Additional pairs of directional terms will be covered in the following lessons, along with additional joint action terms.
● Each term of a pair is the opposite of the other term of the pair.
● These terms do not describe a static location; rather they describe the direction that a body part is moving at a joint.

21. Section 5.11—Flexion/Extension
● What is flexion?
Flexion is movement at a joint so that the ventral (soft) surfaces of the two body parts at that joint come together.
● What is extension?
Extension is the opposite of flexion. It is movement at a joint so that the dorsal (harder) surfaces of the body parts come closer together.
Figure 5-11

22. Section 5.11—Flexion/Extension (cont’d.)
Insert 5-11C
● Generally, flexion of a body part involves an anterior movement of that body part; extension of a body part involves a posterior movement of that body part.
● The exception to this rule is at the knee joint and further distally, illustrated in Figure 5-11c. Flexion in these locations is a posterior movement of the body part and extension is an anterior movement.
Figure 5-11

23. Section 5.11—Flexion/Extension (cont’d.)
● This illustration shows flexion and extension of the hand.
● Where is the axis of movement in these diagrams?
It is at the wrist joint.
Figure 5-11

24. Section 5.12—Abduction/Adduction
● What is abduction?
Abduction is a movement at a joint that brings a body part away from the midline of the body.
● What is adduction?
Adduction is the opposite of abduction; the body part moves closer toward the midline.
● Abduction and adduction of the thigh occur at the hip joint.
Figure 5-12

25. Section 5.12—Abduction/Adduction (cont’d.)
● Abduction involves a lateral movement of a body part.
● Adduction involves a medial movement of a body part.
● Abduction and adduction of the arm take place at which joint?
They take place at the shoulder joint.
Figure 5-12

26. Section 5.12—Abduction/Adduction (cont’d.)
● This diagram illustrates abduction and adduction of the hand at the wrist joint.
● The fingers and toes do not abduct/adduct relative to the midline of the body. Where is the reference line about which abduction/adduction of the fingers occurs?
It is an imaginary line through the middle finger.
● The reference line about which abduction/adduction of the toes occurs is an imaginary line through the second toe.
Figure 5-12

27. Section 5.13—Right Lateral Flexion/Left Lateral Flexion
● What is right lateral flexion?
Right lateral flexion is a movement at a joint that bends a body part to the right side.
● Left lateral flexion is the opposite of right lateral flexion; the body part bends to the left side.
● Around what axis do right lateral flexion and left lateral flexion movements occur?
They occur around an anteroposterior axis.
Figure 5-13

28. Section 5.13—Right Lateral Flexion/Left Lateral Flexion (cont’d.)
● Lateral flexion motions are frontal plane motions of the axial body and are not the same motions as flexion motions, which are sagittal plane motions.
● Figure 5-13c and Figure 5-13d show an anterior view and lateral view (respectively) of right and left lateral flexion of the neck at the spinal joints.
● What is another name for lateral flexion?
Lateral flexion is often called side bending.
Figure 5-13

29. Section 5.14—Lateral Rotation/Medial Rotation
● Lateral rotation is a movement at a joint wherein the anterior surface of the body part rotates away from the midline of the body.
● Medial rotation is the opposite of lateral rotation; the anterior surface of the body part rotates toward the midline of the body.
● Figure 5-14a and Figure 5-14b show lateral and medial rotation of the arm at the shoulder joint.
Figure 5-14

30. Section 5.14—Lateral Rotation/Medial Rotation (cont’d.)
● Lateral and medial rotation movements occur in which plane?
They occur in the transverse plane.
● Lateral rotation and medial rotation are terms that can be used for the body parts of the appendicular skeleton only.
● Figure 5-14c and Figure 5-14d show lateral and medial rotation of the thigh at the hip joint.
Figure 5-14

31. Section 5.15—Right Rotation/Left Rotation
● What are right rotation and left rotation?
Right rotation is a movement at a joint wherein the anterior surface of an axial body part rotates to the right. Left rotation is the opposite; the anterior surface of the body part rotates to the left.
● In what plane do right rotation and left rotation movements occur?
They occur in the transverse plane around a vertical axis.
Figure 5-15

32. Section 5.15—Right Rotation/Left Rotation (cont’d.)
● Figure 5-15b and Figure 5-15c show right rotation and left rotation of the trunk at the spinal joints.
● What two terms are often used when describing the actions of muscles that can rotate an axial body part within the transverse plane?
They are ipsilateral rotation and contralateral rotation.
● Ipsilateral rotation and contralateral rotation do not define joint actions; rather, they indicate the actions of a muscle.
Figure 5-15

33. Lesson 5.4 Objective
Define joint action terms and be able to show examples of each one.

34. Joint Action Terminology Pairs
Specialized Directional Terms:
Plantarflexion/dorsiflexion
Eversion/inversion
Pronation/supination
Protraction/retraction
Elevation/depression
Upward rotation/downward rotation
● The major pairs of directional terms that are used throughout the body were introduced in Lesson 5.3. This list of pairs of directional terms is used for certain actions at specific joints of the body. More of these terms will be added in Lesson 5.5.

35. Section 5.16—Plantarflexion/Dorsiflexion
● What are plantarflexion and dorsiflexion?
Plantarflexion is the movement at the ankle joint wherein the foot moves inferiorly, toward the plantar surface of the foot. Dorsiflexion is the opposite of plantarflexion; the foot moves superiorly toward its dorsal surface.
● In what plane and around what axis do these movements occur?
Plantarflexion and dorsiflexion occur in the sagittal plane and are axial movements that occur around a mediolateral axis.
Figure 5-16

36. Section 5.17—Eversion/Inversion
● Eversion is the movement between tarsal bones wherein the plantar surface of the foot turns away from the midline of the body.
● Inversion is the opposite of eversion; the plantar surface of the foot turns toward the midline of the body.
● At what joint do these movements occur?
They occur at the tarsal joints (i.e., the subtalar joint), not at the ankle joint.
● In what plane and around what axis do these movements occur?
They occur in the frontal plane and take place around an anteroposterior axis.
Figure 5-17

37. Section 5.18—Pronation/Supination
● Why can the hand not pronate and supinate?
The hand cannot pronate and supinate because these motions are not occurring by a motion of the hand relative to the forearm. Pronation and supination are movements of the forearm (not the hand) at the radioulnar joints.
● Pronation is the movement of the forearm wherein the radius crosses over the ulna.
● Supination is the opposite of pronation; the radius uncrosses to return to a position parallel to the ulna.
Figure 5-18

38. Section 5.19—Protraction/Retraction
● What is protraction?
Protraction is a movement at a joint that brings a body part anteriorly.
● Retraction is the opposite of protraction; the body part moves posteriorly.
● Figure 5-19a and Figure 5-19b show protraction and retraction of the mandible at the temporomandibular joint.
Figure 5-19

39. Section 5.19—Protraction/Retraction (cont’d.)
● Figure 5-19c and Figure 5-19d show protraction and retraction of the scapula at the scapulocostal joint.
● Protraction and retraction of the scapula are also known by what other terms?
They are also knows as abduction and adduction of the scapula.
Figure 5-19

40. Section 5.20—Elevation/Depression
● What are elevation and depression?
Elevation is defined as a movement at a joint that brings a body part superiorly. Depression is the opposite of elevation; the body part moves inferiorly.
● Elevation and depression can be axial or nonaxial movements depending on the body part.
● These figures illustrate depression and elevation of the mandible at the temporomandibular joint, which is an axial movement.
Figure 5-20

41. Section 5.20—Elevation/Depression (cont’d.)
● Figure 5-20c and Figure 5-20d show depression and elevation of the scapula at the scapulocostal joint.
● Elevation and depression of the scapula are nonaxial movements. There is no axis around which the motion occurs.
● With regard to elevation/depression of the pelvis, it is worth pointing out that if one side of the pelvis elevates, the other side depresses, and vice versa.
Figure 5-20

42. Section 5.21—Upward Rotation/Downward Rotation
● Upward rotation and downward rotation are terms that may be used to describe the movement of what body parts?
They are used to describe movement of the scapula and the clavicle.
● What is the scaption plane and where is it located?
The actual plane that the scapula moves within is the plane of the scapula, sometimes called the scaption plane, which lies between the sagittal and frontal planes.
Figure 5-21

43. Section 5.21—Upward Rotation/Downward Rotation (cont’d.)
● Figure 5-21b shows the scapula in anatomic position. Figure 5-21c illustrates upward rotation of the clavicle at the sternoclavicular joint. Downward rotation of the clavicle would be returning to anatomic position.
● Upward rotation and downward rotation of the clavicle are axial movements that occur in a transverse plane around an axis that is approximately mediolateral in orientation.
Figure 5-21

44. Lesson 5.5 Objectives
Define joint action terms and be able to show examples of each one.
Explain the two uses of the term hyperextension.
Demonstrate and be able to state the component actions of circumduction.

45. Joint Action Terminology Pairs
Specialized Directional Terms:
Anterior tilt/downward tilt
Opposition/reposition
Lateral deviation to the right/lateral deviation to the left
Horizontal flexion/horizontal extension
● In this lesson, the remaining pairs of directional terms used for certain actions at specific joints of the body will be covered.

46. Joint Action Terminology
Additional Joint Action Terms:
Hyperextension
Circumduction
● The additional terms hyperextension and circumduction will also be covered.

47. Section 5.22—Anterior Tilt/Posterior Tilt
● Anterior tilt and posterior tilt describe movements of the pelvis.
● Anterior tilt is the movement of the pelvis wherein the superior aspect of the pelvis tilts anteriorly.
● Posterior tilt is the movement of the pelvis wherein the superior aspect of the pelvis tilts posteriorly.
Figure 5-22

48. Section 5.22—Anterior Tilt/Posterior Tilt (cont’d.)
● In what plane do anterior tilt and posterior tilt occur?
They occur in the sagittal plane.
● In the frontal plane the term depression (or lateral tilt) of the pelvis is used.
● To learn the tilt actions of the pelvis, it can be helpful to think of the pelvis as a basin that holds water. Whichever way the pelvis tilts, water will spill out in that direction. Figure 5-23 illustrates this point.
Figure 5-23

49. Section 5.23—Opposition/Reposition
● Opposition is the movement of the thumb wherein the pad of the thumb meets the pad of another finger.
● Reposition is the opposite of opposition; the thumb returns to its starting position.
● What are the components of opposition/reposition?
Flexion and extension of the thumb occur in the frontal plane around an anteroposterior axis. Abduction and adduction of the thumb occur in the sagittal plane around a mediolateral axis. Medial and lateral rotation of the thumb occurs in the transverse plane around a vertical axis.
Figure 5-24

50. Section 5.24—Right Lateral Deviation/Left Lateral Deviation
● What is right lateral deviation?
Right lateral deviation is a movement at a joint that brings a body part to the right.
● Left lateral deviation is the opposite of right lateral deviation; the body part moves to the left.
● Lateral deviation of the mandible at the temporomandibular joint (TMJ) is a linear nonaxial movement.
Figure 5-25

51. Section 5.24—Right Lateral Deviation/Left Lateral Deviation (cont’d.)
● Lateral deviation of the trunk is an axial movement that often occurs as the reverse action of a muscle that crosses the glenohumeral joint from the arm to the trunk.
● In Figure 5-25b and Figure 5-25c the hand is holding onto an immovable object and is fixed; when muscles such as the pectoralis major and latissimus dorsi contract, the trunk is laterally deviated to the right, toward the right arm.
Figure 5-25

52. Section 5.25—Horizontal Flexion/Horizontal Extension
● Horizontal flexion is a horizontal movement in an anterior direction of the arm at the shoulder joint or thigh at the hip joint.
● Horizontal extension is the opposite of horizontal flexion; a horizontal movement in a posterior direction of the arm or thigh.
● Figure 5-26 illustrates horizontal flexion and horizontal extension of a person’s left arm at the shoulder joint.
● In what plane do these actions occur?
They occur in the transverse plane.
Figure 5-26

53. Section 5.26—Hyperextension
● The term hyperextension is commonly used in what two ways?
In this text, it is used to denote movement that is beyond what is considered to be a normal or healthy range of motion. However, in other sources, it is also sometimes used to describe normal, healthy extension beyond anatomic position.
● This illustration shows a woman extending her arm at the shoulder joint toward anatomic position; she then “hyperextends” her arm beyond anatomic position. (Note: This text does not adopt this use of the term hyperextension.)
Figure 5-27

54. Section 5.27—Circumduction
● Circumduction is a combination of actions of a body part that occur sequentially at a joint.
● Does circumduction involve some form of rotation?
No rotation occurs during circumduction.
● Which body parts can circumduct?
The arm, thigh, hand, foot, head, neck, trunk, and pelvis can all circumduct.
Figure 5-28

55. Lesson 5.6 Objectives
Explain how oblique plane movements are broken down into their component cardinal plane actions.
Explain the concept of a reverse action and demonstrate examples of reverse actions.

56. Lesson 5.6 Objectives (cont’d.)
Explain how drawing in a vector can help us learn the actions of the muscle.
Draw a vector that represents the line of pull of a muscle; and if the muscle’s line of pull is oblique, be able to resolve that vector into its component cardinal plane vectors.

57. Section 5.28—Naming Oblique Plane Movements
● Figure 5-29 shows movement that is within an oblique plane that is between the sagittal and frontal planes. This one movement is described as flexion and abduction of the arm at the shoulder joint (or abduction and flexion of the arm at the shoulder joint; the order does not matter).
● An oblique plane is a plane that is not purely sagittal, frontal, or transverse. It is instead a combination of two or three cardinal planes.
Figure 5-29

58. Section 5.28—Naming Oblique Plane Movements (cont’d.)
● To describe oblique plane motions, one must state the separate components of the cardinal planes. The analogy to geographic movements, as illustrated here, greatly facilitates this explanation.
● This person is walking in a northwesterly direction. In geographic terms, this movement is describes as northwest, instead of saying that the person is walking north and west.
Figure 5-30

59. Section 5.28—Naming Oblique Plane Movements (cont’d.)
● Figure 5-31 illustrates movement occurring within an oblique plane. This oblique plane is a combination of all three cardinal planes; therefore the movement that is occurring has component actions in all three cardinal planes.
● What movements are taking place in this illustration?
The person is flexing, adducting, and medially rotating the right thigh at the hip joint.
● Does the order of these actions matter?
No, it is not important.
Figure 5-31

60. Section 5.29—Reverse Actions
● What is a reverse action?
A reverse action is when a muscle contracts and the attachment that is usually considered to be more fixed moves, and the attachment that is usually considered to be more mobile stays fixed.
● Figure 5-32a shows a medial view of the brachialis muscle.
● Figure 5-32b shows the brachialis muscle contracting and causing flexion of the forearm at the elbow joint. This is the usual action of the brachialis.
Figure 5-32

61. Section 5.29—Reverse Actions (cont’d.)
● Figure 5-32c illustrates the brachialis muscle contracting to do a pull-up. Since the hand is fixed to the pull-up bar, the arm moves instead of the forearm. The resulting action is flexion of the arm at the elbow joint, which is a reverse action, because the attachment that is usually considered to stay fixed did the moving.
● Figure 5-32d shows both attachments of the brachialis moving, so both the forearm and the arm are flexing at the elbow joint; therefore the usual action and the reverse action are occurring at the same time.
Figure 5-32

62. Section 5.30—Vectors ● What is a vector?
A vector is an arrow drawn to represent the line of pull of a muscle.
● What are the two components of a vector and what do they represent?
The two components of a vector are the arrowhead, which points in the direction of the muscle’s line of pull, and the stem whose length tells us the magnitude of the muscle’s pull.
● The vector in this illustration indicates that the muscle’s line of pull is medial.
Figure 5-33

63. Section 5.30—Vectors (cont’d.)
● The vector in Figure 5-34b represents the direction of fibers and resultant line of pull of the rhomboids upon the scapula.
● The rhomboid’s pull on the scapula is diagonal (i.e., oblique).
Figure 5-34

64. Section 5.30—Vectors (cont’d.)
● To resolve a vector, break down an oblique plane motion into its component cardinal plane motions.
● In this illustration, the vector arrow of the rhomboids is resolved into component green vectors that represent the cardinal plane actions of the rhomboids. The component vector arrows begin at the tail of the vector arrow and end at the vector’s arrowhead. In this case, the horizontal component vector arrow shows that the rhomboids can retract (adduct) the scapula; the vertical component vector arrow shows that the rhomboids can elevate the scapula.
Figure 5-34

65. Section 5.30—Vectors (cont’d.)
● Figure 5-35 shows the vector analysis of the actions of the right coracobrachialis muscle.
● When resolving the vector, which represents the overall pull of the coracobrachialis upon the arm at the shoulder joint, what component vectors should be drawn?
The vertical vector (green) begins at the tail of the yellow arrow and represents the muscle’s ability to flex the arm; the horizontal vector (green) ends at the head of the yellow arrow and represents the muscle’s ability to adduct the arm. Therefore, the coracobrachialis can both flex and adduct the arm at the shoulder joint.
Figure 5-35