Gelenkmoment

Gelenkmoment, literally joint moment, is the rotational effect produced about a joint axis by the forces acting on the body segment(s) connected at the joint. In biomechanics and robotics, it is synonymous with joint torque and represents the net effort required to rotate or stabilize a joint against external loads, gravity, and muscular forces. The moment is measured in Newton-meters (Nm) and depends on the distance (moment arm) from the joint axis to the line of action of the force and on the component of the force that acts to rotate the joint.

Calculation: In a rigid-body model, the moment about a joint axis equals the sum over forces of r × F projected onto the joint axis. In gait analysis and biomechanics, joint moments are often obtained through inverse dynamics, combining kinematic data (segment angles, angular velocities, accelerations) with external forces (ground reaction forces) to compute time histories of joint moments for flexion/extension and other axes. Sign conventions are defined by the chosen axis and positive directions.

Interpretation: The net Gelenkmoment reflects the combined action of all muscles crossing the joint, external loads, and the dynamics of the limb. It does not equal a single muscle force; it is the resultant moment produced by coordinated muscle activity to achieve movement or stabilization. The magnitude and pattern over time provide insight into joint loading, muscle function, and rehabilitation status.

Applications: Gelenkmoments are used in gait analysis, sports biomechanics, rehabilitation engineering, the design of orthoses and prostheses, and robotics to assess joint loading and control strategies, evaluate injury risk, and guide therapeutic or training interventions.