Kinetics and Arthrokinematics Quiz

Introduction to Kinesiology: Chapter 1

• Kinesiology is the study of movement.
• It's crucial for physical therapists because it aids in rational examination, accurate diagnosis, and appropriate treatment.

Kinematics

• Movement is categorized into two types:
  • Translation: Linear motion, which can be straight (rectilinear) or curved (curvilinear).
  • Rotation: Movement around a pivot point or axis.
• Active movement is caused by muscle stimulation.
• Passive movement is caused by forces other than muscle contractions.

Center of Mass (CoM)

• For a standing posture, the CoM is positioned anterior to S2.
• For a seated posture, the CoM is positioned anterior to T12.

Increased Stability of the Body

• Stability depends on the Line of Gravity and the Base of Support (BoS).
• An object is stable only when its Line of Gravity passes through its BoS.

Osteokinematics

• Sagittal Plane: Flexion/extension, Dorsiflexion/Plantarflexion, Forward/Backward bending.
• Frontal Plane: Abduction/adduction, Lateral flexion, Ulnar/radial deviation, Eversion/inversion.
• Horizontal (Transverse) Plane: Internal/external rotation (medial/lateral), axial rotation.

Axis of Rotation

• The axis of rotation passes through the convex bone of the joint.
• Movement at this point is equal to zero (pivot).

Degrees of Freedom (DoF)

• Joints have up to three degrees of freedom (DoF).
• For example, the glenohumeral (shoulder) joint has three DoF, the wrist joint has two DoF, and the humeroulnar (elbow) joint has one DoF.
• Accessory motion refers to slight passive translation of the joints, allowing for assessment of ligament integrity (hypomobility/hypermobility).
• Excessive translation may indicate ligamentous injury or abnormal laxity.

Quantity of Motion

• Range of motion(ROM) is measured to determine degrees of freedom.

Osteokinematic Perspective

• Open Chain: Distal segment moves on a proximal segment (ex. ulna on the humerus in a bicep curl).
• Closed Chain: Proximal segment moves on a distal segment (ex. humerus on the ulna in a tricep press down).

Arthrokinematics

• Roll: Multiple points on one articular surface contact multiple points on another articular surface.
• Slide: A single point on one articular surface contacts multiple points on other articular surface. Some classifications also refer to this as a "glide".
• Spin: A single point on one articular surface rotates on a single point on the other articular surface.
• Roll-slide combination: Occurs together as a limb moves or during certain pathophysiological conditions.
• Ovoid joint rule, otherwise known as the convex/concave rule: Important biomechanic principle seen in various joint types.

Closed- and Loose-Packed Position of Joint

• Closed-packed position: This position maximizes joint congruency and ligament/capsule tightness. Accessory motion is minimal making the joint very stable.
• Loose-packed position: Accessory movements are maximal. The joint is least congruent in this posture.

Kinetics

• Kinetics is a branch of mechanics that describes the effect of forces on the body.
• Force is a push or pull that produces, changes, or stops a movement (F=ma).
• Forces affecting the body include tension, compression, bending, shear, and torsion.

Impact of Forces on the MS System

• Forces can be beneficial or detrimental to the musculoskeletal system.
• Healthy tissue can partially resist changes in structure and shape.
• Weakened tissue may not be able to adequately resist loading.

Stress-Strain Relationship

• Different loading patterns produce different stress and strain effects on tissue. Stress-strain curves can depict these responses.

Creep

• Creep describes the gradual, time-dependent deformation of a material under sustained load, often exhibiting a change of structure over time.

Rate of Loading

• Rate of loading, like running, affects the properties of connective tissue in the body, impacting how much stiffness and stress occurs.

Internal Forces

• Internal forces originate within the body; those stemming from stimulated muscle are the largest.
• Additional internal forces include tension from stretched connective tissues (such as intramuscular CT, ligaments, and joint capsules) as well as from nerves, blood vessels, and skin.

External Forces

• External forces arise from outside the body, these commonly include gravity, external loads, and physical contact.

Force Vectors

• Force vectors are quantities fully specified by magnitude and direction.
• Analysis of force vectors involves:
  • Magnitude (shaft length): Amount of force.
  • Spatial Orientation (shaft of arrow): Position of force line.
  • Direction (arrowhead): Positive (up/right) or negative (down/left).
  • Point of application (base): Location where force acts.

Joint Reaction Force

• A force that exists at the joint
• Reaction to the net internal and external forces
• Includes the force between joint surfaces, actions from bony structures in the periarticular area.

Musculoskeletal Torques

• Force can cause linear or rotational movement
• The resulting rotational movement depends on the moment (lever) arm: distance between the body axis and the point of force application.

Muscle and Joint Interaction

• Overall effect of a muscle force on a joint. Force with moment arm produces torque and force without a moment arm produces a stabilizing force.

Types of Muscle Activation

• Isometric: Constant length, no change in joint angle, internal torque = external torque
• Concentric: Shortening of muscle fibers, internal torque greater than external torque
• Eccentric: Lengthening of muscle fibers, internal torque is less than external torque during muscle lengthening.

Terminology Related to Muscles

• Agonist: Main muscle doing the movement
• Antagonist: Muscle opposing the movement.
• Synergists: Muscles that supplement the agonist muscle.
• Force couple: Muscles contracting at the same time but creating different motions..
• Reciprocal inhibition: Contraction of one muscle group inhibiting the opposing muscle group.
• Co-contraction: Simultaneous contraction of agonist and antagonist muscles for joint stabilization.
• Passive insufficiency: When a two-joint muscle is stretched beyond its optimal range, affecting its ability to produce an action.
• Active insufficiency: When a two-joint muscle shortens beyond its optimal range, affecting its ability to produce powerful movements.

Musculoskeletal Levers

• A structural lever for force transmission, there are three types of levers:
  • First class: Axis of rotation is positioned between the load and the effort. Possible MA values less than 1, equal to 1 or greater than 1. Example: Head and neck.
  • Second class: Load is positioned between the axis of rotation and effort. The MA is greater than 1. Example: Calf muscles.
  • Third class: Effort is positioned between the axis of rotation and the load. The MA is less than 1. Example: Elbow flexor muscles.

Mechanical Advantage

• Ratio of moment arm of force to the moment arm of resistance
• Dictates how work is done by the body
• Shortens the distance over which muscles must contract, amplifying rotational motion around a joint. Example: Muscle force may be less than resistance but still exert the necessary function, based on the mechanical advantage at play.

Basic Structure and Function of Human Joints: Chapter 2

• Joints connect bones, allowing movement.

Joint Classification

• Synarthroses: Fibrous and cartilaginous; little or no movement.
  • Fibrous: Sutures (in skull), teeth (gomphosis), distal tibiofibular joint, forearm (interosseous membrane).
  • Cartilaginous: Symphysis, costal cartilage.
• Diarthroses (synovial): Most joint types of the extremities, considerable movement.

Seven elements of synovial joints

• Articular cartilage
• Articular capsule
• Synovial membrane
• Synovial fluid
• Capsular ligaments
• Blood vessels
• Sensory nerves

Additional elements for some synovial joints

• Glenoid labrum, articular discs, accessory ligaments, and bursa.

Mechanical Classification of synovial joints (See Table 2-1)

• Details of specific joint types including hinge, pivot, condyloid, ellipsoid, ball and socket, and planar movements are outlined.

Hinge Joint

• Motion occurs perpendicular to the axis of rotation in one plane. Examples include the humero-ulnar joint and interphalangeal joints.

Pivot Joint

• Rotational motion occurs in one plane, where the bone spins along an axis parallel with the axis of rotation. Examples include the proximal radioulnar joint and the atlanto-axial joint.

Ellipsoid Joint

• Biplanar motion occurs between paired surfaces, where one is convex and the other concave allowing for flexion/extension and abduction/adduction. Example: Radiocarpal joint.

Ball-and-Socket Joint

• Triaxial motion in three planes. The large convex and concave joint surfaces allow for complete rotation. Example: glenohumeral joint and hip joint.

Plane Joint

• Two flat surfaces slide/rotate in up to two planes or across opposing faces. Examples include intercarpal and intertarsal joints.

Saddle Joint

• Biplanar motion occurs where one side of each bone is convex and the other concave at right angles. Each joint surface fits into the opposing bony structure. Example: Thumb CMC joint.

Condyloid Joint

• Bi or tri-axial movement. A typical example would be the metacarpophalangeal joint.

Simplified Synovial Joint Classification

• A summary of the classification of various joint categories and how they function.

Axis of Rotation

• Imaginary line extending through a joint along which rotation occurs.
• Instantaneous axis of rotation changes during joint motion, and the path it takes is termed the evolute.

Tissues in the Body

• Connective tissue
• Muscle
• Nerve
• Epithelium

Periarticular C.T.

• Types of connective tissues encountered in the periarticular region of a joint, these are the primary tissues that connect the joint structures.

Dense Connective Tissue

• Tissues that resist tension, aid in binding structures, and transfer forces between anatomical structures. Type I collagen is the primary compositional component; relatively low elastin content.

Articular Cartilage

• Hyaline cartilage that distributes and absorbs joint forces, reduces friction.

Fibrocartilage

• High amount of type I collagen
• Provides support and mechanical stabilization for the joint
• Dissipates loads across several planes, important functional role in joint arthrokinematics.

Bone

• Provides structure and support throughout the body.
• Composed of type I collagen, calcium deposits, and other minerals.
• Bone resists deformation and acts as a structural component in leverage.

Factors Affecting Connective Tissue

• Blood supply, age, and immobilization affect connective tissue, delaying recovery and potentially impacting function.

Muscle: the Primary Stabilizer and Mover of the Skeletal System: Chapter 3

• Muscles stabilize bones through postural control, create movement through contraction, and provide shock absorption throughout movement.

Muscle Morphology

• Different muscle shapes impact their functional properties and how their individual shapes and architecture accommodate their role in bodily functions. Examples include strap, fusiform, unipennate, bipennate, multipennate, quadrilateral, digastric, tricipital, triangular, and cruciform.

Muscle Architecture

• Physiological cross-sectional area (Sum = volume/length) relates to force potential; thicker muscles generate greater force than thinner muscles.
• Pennation angle refers to the oblique arrangement of muscle fibers relative to the tendon. A higher pennation angle results in more force vector parallel with the tendon in a given muscle.

Muscle & Tendon: Force Generation

• Passive Tension from series elastic components (tendon & Titin), provides tension when muscles are stretched.
• Parallel Elastic Components from epimysium, perimysium, and endomysium provide essential support for muscle structure and function.
• Muscles generate force as a response to external loads using the series and parallel elastic components of connective tissue and contractile proteins.

Active Length-Tension Curve

• Ideal resting length of muscle fiber
• Describes the relationship between muscle length and its ability to generate active force

Internal Torque-Joint Angle Curve

• Internal torque (force exerted by muscles) changes as the joint angle fluctuates.
• Torque is greater in concentric contractions compared to isometric contractions; torque (force production) is maintained, despite changes in muscle and bony structure length.

Muscle as a Skeletal Mover: Force Modulation

• During concentric and eccentric movements, a precise relationship between a muscle's maximal force and its contraction (elongation) velocity is established.

Max Muscle Force & Speed of Contraction

• The relationship between muscle load and contraction velocity is examined, including concentric, isometric and eccentric muscle contraction types.

Force-Velocity Curve

• Concentric: Amount of muscle force is inversely proportional to the velocity of muscle shortening.
• Eccentric: Amount of muscle force is directly proportional to the velocity of muscle lengthening.
• Isometric: Zero velocity
• Muscle force is greatest in the eccentric phase.
• Relationship between muscle contraction speed and the force generated at such a rate

Comparing Activations

• Eccentric contraction results in the greatest average force production per crossbridge. This is due to several factors, including quicker reattachment of crossbridges and the viscoelastic properties within the fibers.

Functional Significance

• Less effort and more efficient movements arise from eccentric muscle contractions; elongated muscles store energy for concentric contractions.

Positive vs. Negative Work

• Positive work performed during concentric actions versus negative work during eccentric actions.

Activating Muscle via the Nervous System

• Motor units (MUs) consist of motor neurons and the muscle fibers they innervate.
  • Smaller motor units produce fine motor control and small forces; larger MUs are for less refined movements and greater force production.

Recruitment

• Muscle recruitment involves activating more motor units to generate greater force.
• Small motor units are recruited earlier than large ones. Recruitment orders can influence the rate at which a muscle must contract (faster or slower rates).

Test your knowledge on kinetics, joint mechanics, and arthrokinematics with this quiz. Explore concepts related to forces, joint positions, and tissue response in the human body. Perfect for students in anatomy or physical therapy courses.