Physics: Kinematics and Arthrokinematics
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Questions and Answers

What is the state in which there is no acceleration?

  • Arthrokinematics
  • Kinematics
  • Dynamics
  • Equilibrium (correct)

    • What type of motion occurs when a joint moves?

  • A combination of rolling, sliding, and spinning (correct)
  • Only spinning
  • Only rolling
  • Only sliding

    • What happens in a pure rolling motion?

  • The same point on one surface contacts new points on the other surface
  • The surfaces do not move
  • Each subsequent point on one surface contacts a new point on the other surface (correct)
  • There is no contact between the surfaces

    • Why is the combination of rolling, sliding, and spinning important in joint movement?

    <p>To permit a large range of motion while using a small articular surface</p> Signup and view all the answers

    What happens to the femur during the last part of knee extension?

    <p>It spins (internally rotates) on the tibia</p> Signup and view all the answers

    What would happen to the knee joint if there were only rolling of the condyles of the femur on the tibial plateau?

    <p>The knee would dislocate</p> Signup and view all the answers

    What occurs during anterior movement of the tibia?

    <p>An anterior movement of the concave tibial plateau on the femur</p> Signup and view all the answers

    What is the point of congruency in joint pairs called?

    <p>Close-packed position</p> Signup and view all the answers

    In which joint does the close-packed position occur at dorsiflexion?

    <p>Ankle joint</p> Signup and view all the answers

    What is the term for the position where the ovoid joint surfaces do not fit perfectly?

    <p>Loose-packed position</p> Signup and view all the answers

    In which joint does the close-packed position occur at full extension?

    <p>Elbow, Wrist, Hip, and Knee joints</p> Signup and view all the answers

    What occurs when the joint is in a close-packed position?

    <p>The joint is mechanically compressed and difficult to distract</p> Signup and view all the answers

    What is the advantage of the close-packed position in the hip and knee joints during standing?

    <p>It provides an economy of energy expenditure</p> Signup and view all the answers

    What type of motion occurs in addition to angular motions in a joint?

    <p>Translatory motion</p> Signup and view all the answers

    What is the result of the close-packed position in the MPJs during gripping action?

    <p>Mechanical advantage</p> Signup and view all the answers

    What is the state of the ligamentous and capsular structures in the open-packed position?

    <p>Slack and relaxed</p> Signup and view all the answers

    What is the benefit of the close-packed position in terms of joint stability?

    <p>It reduces the need for muscle forces</p> Signup and view all the answers

    What is the consequence of larger joint surfaces in the context of Range of Motion (ROM)?

    <p>ROM would be limited</p> Signup and view all the answers

    What occurs in an open kinematic chain?

    <p>The distal segment moves in space while the proximal segment is fixed or stable</p> Signup and view all the answers

    Which of the following is an example of a closed-chain motion?

    <p>Performing a squat</p> Signup and view all the answers

    What happens to the thigh in the motion of standing to sit?

    <p>The thigh approaches the pelvis</p> Signup and view all the answers

    What type of motion occurs during walking and stair climbing?

    <p>Alternation of closed-chain motion and open-chain motion</p> Signup and view all the answers

    What happens to the leg in the motion of standing up from a chair?

    <p>The leg moves forward on the fixed foot (dorsiflexion)</p> Signup and view all the answers

    What type of end-feel occurs when the motion is stopped by contact of bone on bone?

    <p>Hard or Bony End-feel</p> Signup and view all the answers

    Which type of end-feel is characterized by pain on motion but absence of resistance?

    <p>Empty End-feel</p> Signup and view all the answers

    What type of end-feel occurs when the limitation is from ligamentous, capsular, or muscle structures?

    <p>Firm or Springy End-feel</p> Signup and view all the answers

    What is the term for a normal end-feel that is not characteristic of the normal joint end-feel and occurs at a different place in the ROM of a joint?

    <p>Pathologic end-feel</p> Signup and view all the answers

    Which type of end-feel is characterized by a rebound feel at the inner of ROM?

    <p>Springy end-feel</p> Signup and view all the answers

    What type of end-feel occurs when the motion is stopped by the contact of adjacent soft tissues?

    <p>Soft End-feel</p> Signup and view all the answers

    Study Notes

    Kinematic Chains

    • A kinematic chain refers to a series of articulated segmented links, such as the connected pelvis, thigh, leg, and foot of the lower extremity.
    • There are two types of kinematic chains:
      • Open kinematic chain: the distal segment of the chain moves in space while the proximal segment is fixed or stable.
      • Closed kinematic chain: the distal segment is fixed, and proximal parts move.

    Examples of Kinematic Chains

    • Squat: an example of a closed-chain motion.
    • Leg curl from sitting in a chair: an example of an open-chain motion.
    • Reaching or bringing the hand to the mouth: an open-chain motion.
    • Performing a chin-up: a closed-chain motion.
    • Standing to sit and sitting down in a chair: both are closed-chain motions.
    • Walking and stair climbing: alternation of closed-chain motion and open-chain motion.

    Convex-Concave Principle

    • Normal interphalangeal joint movements follow the convex-concave principle.
    • Close-packed position: the ovoid surfaces of joint pairs match each other perfectly in only one position of the joint, usually occurring at one extreme in the range of motion.
    • Open-packed position: the ovoid joint surfaces do not fit perfectly and are incongruent.

    Characteristics of Close-Packed Position

    • Maximum area of surface contact occurs.
    • The attachments of the ligaments are farthest apart and under tension.
    • Capsular structures are taut (under tension).
    • The joint is mechanically compressed and difficult to distract.

    Characteristics of Open-Packed Position

    • The ligamentous and capsular structures are slack.
    • The joint surfaces may be distracted several millimeters.
    • This position allows the necessary motions of spin, roll, and slide and may decrease joint friction.

    Mechanical Advantage of Close-Packed Position

    • Provides great mechanical stability to the joint.
    • Reduces the need for muscle forces to maintain a position.
    • Examples: standing position, gripping action.

    Accessory Motions

    • Joint surfaces can be moved passively a few millimeters in translatory motion, called accessory movements or joint play.
    • Examples: equilibrium, dynamics.

    Arthrokinematics

    • Three types of motion can occur between the two articulating surfaces: rolling, sliding, and spinning.
    • In a pure rolling motion, each subsequent point on one surface contacts a new point on the other surface.
    • In sliding and spinning, the same point on one surface contacts new points on the mating surface.
    • Most normal joint movement has some combination of rolling, sliding, and spinning.
    • The knee joint shows the combination of these movements most clearly.

    Arthrokinematics in Sit-to-Stand

    • Rising from a seated to a standing position: the femur is extended on the fixed tibia, the femoral condyles roll and slide so that they are always in contact with the tibial condyles.
    • In the last part of knee extension, the femur spins (internally rotates on the tibia).

    Clinical Importance of Arthrokinematics

    • Arthrokinematics (combination of roll, slide, and spin) permits a large range of motion while using a small articular surface.
    • If joints possessed only one of these motions, this would limit the range of motion.

    End-Feel

    • The end-feel is the resistance felt at the end of the range of motion.
    • Normal end-feel: hard, firm, or soft.
    • Examples: hard or bony end-feel, firm or springy end-feel, soft end-feel.
    • Pathologic end-feel: an end-feel that is not characteristic of the normal joint end-feel and occurs at a different place in the range of motion.
    • Examples: empty end-feel, hard end-feel, springy end-feel, sudden hard-feel, capsular feel.

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    Description

    Test your knowledge of kinematics and arthrokinematics concepts, including equilibrium, dynamics, and types of motion in joints.

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