E4 Load Distribution

Topic

Load distribution models how external and internal forces are transmitted through the body's joint and skeletal structures.

External forces are the first type modeled: body weight—acting constantly on joint and skeletal structures due to gravity—and additional loads a person holds, lifts, or carries, which add to body weight and increase the total force these structures must bear.

Alongside external forces, load distribution also models internal forces: the force generated by contracting muscles to support or move the body, and the resistive force of ligaments stretching to hold a joint together. Both internal forces combine with external forces to alter the total load ultimately borne by each joint or skeletal structure.

When combined, external and internal forces are transmitted through joint and skeletal structures, generating articular contact pressure at every point where two joint surfaces meet; the greater the total force passing through a joint—and the smaller the surface area over which that force is distributed—the higher the articular contact pressure borne by that area.

Based on these contact pressures, load distribution analysis identifies zones of overload: areas where articular contact pressure exceeds that of the rest of the structure because they concentrate greater force, a smaller contact area, or both.

Identifying these overload zones allows load distribution analysis to predict the risk of tissue damage: the closer the articular contact pressure in an overload zone comes to the failure threshold of the supporting tissue, the greater the risk that the area will sustain an injury.

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