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Related Concept Videos

Relative Motion Analysis using Rotating Axes01:25

Relative Motion Analysis using Rotating Axes

Consider a component AB undergoing a linear motion. Along with a linear motion, point B also rotates around point A. To comprehend this complex movement, position vectors for both points A and B are established using a stationary reference frame.
However, to express the relative position of point B relative to point A, an additional frame of reference, denoted as x'y', is necessary. This additional frame not only translates but also rotates relative to the fixed frame, making it instrumental in...
Uncertainty in Measurement: Reading Instruments02:46

Uncertainty in Measurement: Reading Instruments

Counting is the type of measurement that is free from uncertainty, provided the number of objects being counted does not change during the process. Such measurements result in exact numbers. By counting the eggs in a carton, for instance, one can determine exactly how many eggs are there in the carton. Similarly, the numbers of defined quantities are also exact. For example, 1 foot is exactly 12 inches, 1 inch is exactly 2.54 centimeters, and 1 gram is exactly 0.001 kilograms. Quantities...
Relative Motion Analysis using Rotating Axes-Problem Solving01:29

Relative Motion Analysis using Rotating Axes-Problem Solving

Consider a crane whose telescopic boom rotates with an angular velocity of 0.04 rad/s and angular acceleration of 0.02 rad/s2. Along with the rotation, the boom also extends linearly with a uniform speed of 5 m/s. The extension of the boom is measured at point D, which is measured with respect to the fixed point C on the other end of the boom. For the given instant, the distance between points C and D is 60 meters.
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Rotational Motion about a Fixed Axis01:26

Rotational Motion about a Fixed Axis

A rigid body's rotation around a fixed axis makes every point within it trace a circular path around a specific line or point. The term given to this type of spinning is defined by the angular position, symbolized by the angle θ. This angle is gauged from a static reference line to the revolving object. From this angular position, any variation is referred to as angular displacement, denoted by dθ. The extent of this displacement can be calculated in degrees, radians, or revolutions, where one...

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Related Experiment Video

Updated: Jun 24, 2026

Isokinetic Robotic Device to Improve Test-Retest and Inter-Rater Reliability for Stretch Reflex Measurements in Stroke Patients with Spasticity
08:40

Isokinetic Robotic Device to Improve Test-Retest and Inter-Rater Reliability for Stretch Reflex Measurements in Stroke Patients with Spasticity

Published on: June 12, 2019

Interobserver and intraobserver reliability in the evaluation of mechanical axis deviation.

J Eric Gordon1, Ryan C Chen, Matthew B Dobbs

  • 1Department of Orthopaedic Surgery, Washington University School of Medicine, St Louis, MO, USA. Gordone@wudosis.wustl.edu

Journal of Pediatric Orthopedics
|March 24, 2009
PubMed
Summary

Assessing lower extremity alignment using the lateral distal femoral angle (LDFA), medial proximal tibial angle (MPTA), and mechanical axis deviation (MAD) shows excellent reliability. These measurements are dependable for evaluating varus or valgus deformities, regardless of observer experience.

Related Experiment Videos

Last Updated: Jun 24, 2026

Isokinetic Robotic Device to Improve Test-Retest and Inter-Rater Reliability for Stretch Reflex Measurements in Stroke Patients with Spasticity
08:40

Isokinetic Robotic Device to Improve Test-Retest and Inter-Rater Reliability for Stretch Reflex Measurements in Stroke Patients with Spasticity

Published on: June 12, 2019

Area of Science:

  • Orthopaedic surgery
  • Radiographic analysis
  • Biomechanical assessment

Background:

  • The lateral distal femoral angle (LDFA), medial proximal tibial angle (MPTA), and mechanical axis deviation (MAD) are standard metrics for evaluating lower extremity alignment.
  • Previous studies have not established the interobserver and intraobserver reliability of these crucial measurements.

Purpose of the Study:

  • To assess the interobserver and intraobserver reliability of LDFA, MPTA, and MAD measurements.
  • To determine if observer experience influences the reliability of these lower extremity alignment assessments.

Main Methods:

  • Three observer groups (surgeons, residents, interns) measured LDFA, MPTA, and MAD on 35 full-leg standing AP teleroentgenograms.
  • Measurements were repeated by each observer at least two weeks apart to evaluate intraobserver reliability.
  • A diverse range of lower extremity alignments (varus, valgus, normal) were included.

Main Results:

  • All measurements demonstrated excellent interobserver and intraobserver reliability (≥0.90), irrespective of observer experience.
  • Mean interobserver differences were 1.6 degrees for angles and 3.1 mm for MAD.
  • Mean intraobserver differences were 1.4 degrees for angles and 1.9 mm for MAD.

Conclusions:

  • Measurement of LDFA, MPTA, and MAD exhibits high reliability among observers.
  • The experience level of the orthopaedic professional does not significantly impact the reliability of these lower extremity deformity assessments.