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Risk Factors and Sources of Injury > Palmar Flexion when Worksurface is Too High         
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Palmar Flexion when Worksurface is Too High

Sitting At A Height Adjustable DeskWhat is Palmar Flexion?

The natural position of the hand when extended is with the fingertips level with or slightly below the wrist. When the hand is angled downward from this position, the resulting position is called palmar flexion. This greatly reduces blood flow through the wrist and can quickly cause pain, fatigue and numbness.

Most standard desks are 29" high, which is (on average) the ideal height for someone who is 6' 0" tall.  Individuals shorter than this who make no other modifications and place the keyboard and mouse on the desktop will be in a position of palmar flexion.  The image at right shows the ideal positioning for a user, with no modifications to the workstation.

Why is Palmar Flexion a Risk Factor?

The position of Palmar Flexion reduces blood flow through both constriction of the ulnar artery as well as the accompanying sustained muscle tension. The result is a significant reduction in blood flow to the muscles of the hand and forearm. The median nerve also runs through the carpal tunnel in the wrist, and when adopting a position of Palmar Flexion the span of this tunnel is compressed. The accompanying increase of pressure on this nerve can lead to Carpal Tunnel Syndrome.  It can also eventually lead to Dupuytren's Contracture (Palmar Fibromatosis), which reduces the ability of the fingers to fully extend.

How Much Palmar Flexion is "OK" and not a Risk Factor?

For most individuals, even a minimal amount of Palmar Flexion will cause some discomfort and is a potential risk factor.

What are the Symptoms of "Too Much" Palmar Flexion?

Typically the initial indication will be a lump in the palm of the hand near the base of the fingers, which can present with or without accompanying pain.  As it progresses, a reduction in the flexibility (especially when using the extensor muscles to open the hand fully) and pain in the fingers can occur.

How can the Choice of Workstation Help to Reduce Palmar Flexion?

Adjustable Height or Sit Stand Workstations can be adjusted to the correct height for the user, which will not only reduce but will eliminate the position of palmar flexion.  On worksurfaces that are too high, the addition of an Articulating Keyboard Arm can bring the keyboard and mouse below the worksurface to the appropriate height for the individual.

What Other Strategies can be used to Reduce Palmar Flexion?

Most chairs have the ability to adjust in height. By raising the height of the seat, it may be possible to achieve the proper relative arm height. Note: This will usually also require the addition of a Foot Rest to prevent dangling feet.   

Often individuals will adopt positions of Palmar Flexion while they are asleep (without realizing it). The wearing of a wrist brace or support while sleeping can prevent accidental adoption of a position of Palmar Flexion when one is supposed to be at rest.


Last edited July 20th, 2018

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