Symmetrical Axis of Rotation Approach (SARA) is an optimization algorithm that uses function calibration frames between a Parent and Child segment to estimate the Axis of Rotation. The Parent and Child segments are expected to be rigid, these can either use Rigid Cluster or Skin Based Markers + OSCT processing.

The main value of this operation is to provide a more repeatable Knee Joint Axis. SARA locates the joint axis only, Kinematic and Kinetics are still calculated by a Full Biomechanical Model (ie Plug-in Gait).

The SARA method has been implemented in Nexus 2.

Research Publication: Rainald M. Ehrig, William R. Taylor, Georg N. Duda, Markus O. Heller. A survey of formal methods for determining functional joint axes. Journal of Biomechanics 40 (2007) 2150–2157