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Knee Displacement

Overview​

Displacement measured at the knee represents the movement of the knee in impact scenarios and can provide insight into the risk of lower extremity injuries, as knee movement may influence the forces or motion experienced by surrounding anatomy [1]. For example, high levels of displacement at the knee may indicate large forces being transferred from the femur into the pelvis, which could result in hip or pelvic fractures [1]. Additionally, if an Injury Assessment Reference Value (IARV) is associated with the ATD used in the selected load test, the calculated maximum lateral force will be reported as a percentage of the IARV [2]. The IARV is a threshold value used to assess injury risk during an impact. Each ATD has its own IARV, which varies depending on the type, sex, and size of the dummy [2].

Required Signals​

  • Displacement at the Left and Right Knee (X)
  • Displacement at the Left and Right Femur (X)

Calculation​

  1. Convert knee displacement to millimeters (mm) (if applicable)
  2. Filter the displacement signal (CFC = 180)
  3. Truncate displacement signal to start at 0 seconds (if applicable)
  4. Calculates the minimum filtered displacement value and inverts value
  5. Calculates the percent of the IARV threshold that the minimum filtered knee displacement value reaches

References​

[1] Huelke D, O'Day J, States J. "Lower Extremity Injuries in Automobile Crashes". The University of Michigan and University of Rochester, March 1981.

[2] Rupp J, Miller C, Reed M, Madura N, Ritchie N, Schneider L. "Characterization of Knee Impacts in Frontal Crashes". The University of Michigan Transporation Research Institute, Paper 07-0345.