Kinesiology Flashcards
Joint Movement
The movement at a joint occurs in pairs of opposing movements. In other words, if the joint can move forward it can generally move backward, if it moves inward than it should also move outward. The bones that form the joint will move toward one another or away from one another during an action. Generally, there is a greater degree of range of motion available when the bones are moving toward one another than when they are moving away from one another. This arrangement creates a more stable musculoskeletal system.
The amount of movement will be determined by the natural length of the muscles, tendons crossing the joint, and shape of the bone itself. Bony opposition is when bony structure determines the limit of movement, such as the olecranon at the elbow. Some bones, such as the patella, actually help the joints to follow a track smoothly to increase range. Ligaments are particularly critical in limiting movement, so as to create stability in the skeletal system and to prevent hypermobility or excessive movement. Therefore, we must take into consideration all of these effects when we see an animal in movement and are trying to assess how the muscles may be affected.
Types of Joint Movements:
Flexion and Extension
Flexion and Extension The most common pair of joint movements is flexion and extension. These joint movements are in opposition to one another. Picture an animal (or human) in the fetal position. All joints are in a state of flexion when in the fetal position. The opposite movement, exiting the fetal position, is extension. Here is another example; your elbow is in flexion when your arm is bent and in extension when your arm is straight.
- Flexion: Movement occurs in a sagittal plane and decreases the angle formed at the articulation of the bones. Flexion is the movement closing the joint, bringing two bones closer together, or decreasing the joint angle.
- Extension: Movement occurs in a sagittal plane and increases the angle formed at the articulation of the bones. Extension is the opening of the joint moving two bones apart or increasing the joint angle.
Types of Joint Movements:
Abduction and Adduction
Abduction and Adduction Abduction and adduction apply to the relationship between the limbs and the body or mid-line. Adduction and abduction occur at the hip and shoulder.
- Abduction: Movement occurs in a transverse plane and takes the limb lateral or away from the midline of the body. Abduction means to take away, so abduction is the movement of the limb away from the mid-line of the body such as when you raise your arm to the side.
- Adduction: Movement occurs in a transverse plane and takes the limb medial or toward the midline of the body. Adduction means to add to the body, moving toward or even across the mid-line such as when you place your hand over your heart.
Types of Joint Movements:
Lateral Flexion
Lateral Flexion This movement should not be confused with flexion described above. Lateral flexion describes flexion to one side and is specific to the axial skeleton, the spinal column, and skull.
Any portion of the midline, to varying degrees, can flex sideways, as in going around a curve or turning to scratch an itch. In this movement, muscles on one side of the body are contracting while the same muscles on the opposite side are lengthening to allow the movement. This is called unilateral action because the movement occurs to one side (uni = one).
Since the movement is also lateral flexion, it ends up a mouthful; unilateral lateral flexion. Unilateral lateral flexion is distinguished from bilateral flexion (generally called flexion) where the muscles on both sides are moving in tandem, not in opposition. In this textbook, we will use the word flexion to describe bilateral flexion and the term lateral flexion to describe unilateral lateral flexion, which is needlessly redundant. However, since you may see these terms used in other literature, we have taken the time to note them here. An example of bilateral flexion is when you lower your head and neck toward your chest.
Types of Joint Movements:
Rotation
Rotation Rotation involves movement around an axis or point, like the lid of a jar. Rotation occurs along the spine at the facet joints. The neck is the most mobile aspect of the spine and the atlantoaxial joint between the first and second cervical is responsible for the greatest degree of rotation. The second cervical vertebrae, you will remember, is called the axis and has a finger-like projection around which the first cervical vertebrae can turn or rotate.
• Rotation: Movement occurs around the circumference of the joint creating a rolling motion. Rotation is limited in quadrupeds. It occurs along the spine and in the limbs
Types of Joint Movements:
In the limbs, rotation is either internal (medial) or external (lateral).
- Internal Rotation (medial): When the front (cranial aspect) of the limb turns towards the mid-line. An example is when you look at your watch. The opposite movement is external or lateral rotation.
- External Rotation (lateral): When the cranial aspect of the limb rotates away from the midline. An example would include hitch-hiking.
Joint Action:
Flexion
Movement Description:
Decreasing joint angle
Joint Action:
Extension
Movement Description:
Increasing joint angle
Joint Action:
Abduction
Movement Description:
Movement away from body midline
Joint Action:
Adduction
Movement Description:
Movement toward body midline
Joint Action:
Rotation
Movement Description:
Rotation about and axis
Joint Action:
Circumduction
Movement Description:
Movements that create a complete circle (as opposed to a rotation of less than 360 degrees.) A joint that cab do flexion, extension, abduction, adduction, and rotation
Movements of the Canine Body:
Head and Neck
The head and neck are the most mobile aspect of the axial skeleton. Various factors can affect the health of the muscles in this region, including feeding habits, tooth structure, collars, and handling or conformation. Any of these items can cause an animal to adopt a posture which is more comfortable in the short-term, but inefficient for long-term performance.
Movements of the Canine Body:
Head
The movements of the head: • Flexion • Extension • Lateral flexion • Rotation
The first two joints of the cervical spine are responsible for the yes and no movements of the head. The greatest amount of flexion and extension occurs at the atlanto-occipital joint between the skull and first vertebrae (the “yes” movement). The greatest amount of rotation occurs at the atlantoaxial joint between the first and second vertebrae (the “no” movement).
Other muscular movements possible at the head include the movements of the jaw:
• Depression: Opening of the jaw • Elevation: Closing the jaw
There are also movements of the eyes and nose and a tremendous scope of movement at the ears.
Movements of the Canine Body:
Neck
Neck movements occur at the articulations of the seven cervical vertebrae and the first thoracic vertebra.
The movements of the neck: • Flexion • Extension • Lateral flexion • Small degrees of rotation
A crucial aspect of the head and neck anatomy is the nuchal ligament. This ligament runs from the base of the skull to the area of the withers like a rope or cord. It is continuous with the supraspinous ligament which ends at the sacrum. It serves as an attachment site for several important muscles
Movements of the Canine Body:
Shoulder and Forelimb
The muscling of the shoulder and forelimb along with the skeletal structure determine the quality of movement at the shoulder. As discussed earlier, the shoulder of the dog does not possess a clavicle or a shoulder girdle. Instead, a sling of soft tissue structures (muscles, tendons and ligaments) supports the scapula. This sling allows the shoulder to swing in a pendulum like fashion and to be supported between the two pillars formed by the legs like a hammock. Proper shoulder muscling should blend well with the neck and trunk. Excessive development in any one muscle or group of muscles may cause faulty movement or posture.
Movements of the Canine Body:
Shoulder
While the human scapula lies along the back, the animal’s scapula lies along the sides of the ribcage. The shoulder movement is primarily: • Flexion • Extension
The shoulder has less range of motion in: • Abduction • Adduction • Internal rotation • External rotation
The gliding nature of the scapulothoracic joint allows minute degrees of movement in nondescript planes.
Movements of the Canine Body:
Forelimb- Elbows, Wrists, Digits
Below the shoulder, the joints are primarily designed for: • Flexion • Extension
The smaller metacarpal bones and the sesamoids between the digits also allow for gliding movements to reduce friction and concussion.