Part 3: Why Does Carpal Tunnel Syndrome Occur? Structural Explanation.

Why does it happen? Tendons, which connect the muscle to bone, are made of primarily collagen which has high tensile strength. This means that they can withstand a lot of stretch when pulled in the direction of the fibers. For an example, an elastic band is easy to pull length-wise, but not width-wise. When the wrists are mainly straight (also known as neutral position), the tendons are subjected to tensile strength. When the wrists are bent forward or backwards (flexed or extended respectively as seen in the bottom picture), the tendons are exposed to compressive and frictional forces, a position in which the tendons are not structurally strong. The nerves are also compressed or stressed, when the wrist is flexed or extended respectively. When the wrists are deviated to the right or left (seen in the top part of the picture), shear forces are increased. So it can be concluded that straight wrists will be less stressful on the tendons and therefore are less likely to result in injury.

Problems occur when the wrists are flexed, extended or deviated, repeatedly and/or for a long duration.

This ergo-tip is a part of an ergo-tip series about musculoskeletal injuries. Please visit the table of contents at for other available posts. There will be one post released every Tuesday.