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The following is informational only. See a doctor for professional medical advice.


An awesome feature of split keyboards like the Kinesis Advantage, Ergodox, and Corne are their thumb keys. They’re often advocated based on that thumbs are the strongest fingers, and thumb keys offload work from the pinkies: “thumbs good, pinkies bad.”

Left hand on a couple keyboards with thumb key clusters. Left: Dactyl Ergodox. Right: ZSA Moonlander.

Unfortunately, it is not all roses. Thumbs are strong, but not invincible. People can and do get thumb injuries from typing. Furthermore, thumbs are built and move in ways that are biomechanically distinct from the other fingers, so their susceptibility to injury are not entirely comparable.

Don’t get me wrong, multiple thumb keys are a fantastic tool. I wish more keyboards had them. The point is to take it in measure and not overdo it.

Dear reader, if you are interested in this topic, I assume you might have concerns about your thumbs. Please be careful that RSI can escalate quickly and irreversibly. If you have pain, it is important to see a doctor promptly.


Here are some stories of thumb pain related to typing. I am grateful to the folks who shared these so that we may learn from their experience.

On smaller keyboards

40% keyboards tend to make heavy use of thumb keys, so the possibility of injury there is especially concerning. About half of these stories involve the popular Corne and other small keyboards.

Larger keyboard users are affected too, they are represented in the following section.


u/copyconvert (2023-03-12). r/crkbd - RSI in thumb?

Does anyone find the outer thumb keys to be too far under the palm? I started using the corne to reduce the strain on my pinkies, and now my thumb hurts! :D I’ve set up the thumb keys to be layer switches. Number layer is the central thumb key on hold on both hands, with number pad on right hand, arrow keys is the outer thumb key on the right hand with arrows on the right hand

u/Xenioo (2022-10-11). r/ErgoMechKeyboards - Corne: Huge pain in the shoulder, thumbs and wrists

I always felt a discomfort using my corne, but thought it was because of the fact that I was tense due to not being used to it. Now ? I’m feeling real and important pain that makes my daily life really harder. My right thumb is hurting as hell, at first I thought it was because I was hitting the keycaps on the side. But the pain is searing through to the base of the thumb now, it’s almost unbearable

u/azzamsa (2022-06-12). r/ErgoMechKeyboards - Am I the only one that had issue with Corne thumb cluster style?

I feel like the thumb cluster on Corne is a bit inward. To hit the innermost key, I need to curl my thumb. In a long session, it leads to a pain in my hand. […] For small average Asian hands like me, this is an issue. Isn’t this issue more pronounced for people with a larger hand?

u/200orcs (2021-09-17). r/ErgoMechKeyboards - Thumb Pain ergonomics

I have pain in my thumbs, mostly in the right hand. No other finger or wrist issues. Currently I have a Corne, but I find the thumb cluster causes soreness. I think I need a keyboard without a thumb cluster that gets used for layers because the act of holding down a button sucks.


u/fowlie (2023-03-07). r/ErgoMechKeyboards - How to solve thumb fatigue?

I’ve been typing on a Cantor remix with Miryoku for about a year now. When I switched, my wpm dropped to like 20wpm. Now that my wpm is up to ~90wpm, I am starting to notice a thumb fatigue when I type as fast as I can. […] My main issue is, I think that the thumb cluster should be placed one key position further outwards, so that I don’t get my thumb folded back in under my other fingers as much. That way my fingers would strech more.


u/ThatChapThere (2022-11-11). r/olkb - I’m becoming a bit skeptical of multiple thumb keys, especially on a planck

I’ve been using a planck for a few weeks now, and while I don’t miss reaching in order to press symbols, the tendons in my forearms hurt after a while unlike on regular keyboards. They hurt most when pressing thumb keys. It’s not the pressing down that seems to be the problem, more the act of curling them under my palms.

Fingerpunch FFKB

u/knoted29 (2022-11-06). r/ErgoMechKeyboards - RSI - De Quervain’s Tenosynovitis from layer hold on extended thumb

Hi, I’m just wondering if anyone else has gotten RSI with a positive “Finkelstein’s Test for De Quervain’s Tenosynovitis”? The Ergonomist at work almost immediately diagnosed the cause as overuse of the Layer Hold key on the thumb while fully extended. Apparently neutral or tucked is OK, but extended is bad.


u/rhsanborn (2022-06-13). r/ErgoMechKeyboards - Skeletyl Thumb Pain

I love the sculpt of the Skeletyl, but my thumb hurts when I use it for any length of time. It looks like my thumb has to be in a really weird position to get to the thumb cluster. Am I just unlucky that my hand doesn’t fit?

On larger keyboards


u/raynethedark (2022-04-16). r/ergodox - Pain in the wrist/thumb

So I have been using my Moonlander for over a month now and the pain in my wrist/thumb/shoulder is terrible. I have tried adjusting the thumb area, the tilt, and the angle of the boards but nothing is helping. Any advise? I feel like the pain is from the design of the thumb cluster, I have small hands so I feel like it’s too far away even when tilted up…..

Miles McBain (2021-06-19). 60 Days with the ZSA Moonlander: Review

What I do know for sure is that with these hands I couldn’t find a way to use the thumb cluster without pain. Inflammation in my thumbs and wrists slowly accumulated during my time with the Moonlander, and really started to worry me around week 3 - 4 when I noticed pain away from the keyboard when I was doing things like gripping a steering wheel or holding a cup of coffee. The locus of pain was centred at the base of both thumbs running up to my second knuckle and back toward my wrists. I tried all sorts of things to get relief.

Kinesis Advantage

u/ConnorMooneyhan (2022-12-03). r/kinesisadvantage - Thumbs hurt on Advantage360

I never had finger pain before switching to the Advantage360 a few days ago, and now my right thumb just feels awful. I’m trying to relax it and not have it flexed all the time, and that helps a bit, but has anyone else experienced when getting used to the thumb clusters? Any tips?

u/albatrossninja (2021-05-14). r/ErgoMechKeyboards - Thumb Pain from Kinesis Advantage 2

I have a Kinesis Advantage 2, and I absolutely love it. I’ve been using it for around a year, and it really saved my wrists when I switched over, but lately I’ve gotten pretty severe tendonitis in my left thumb. I moved some of the mod keys to the pinky but it kind of defeats the purpose of the advantage. My hands are around average sized but aren’t exactly huge.

adreamer (2021-03-17). geekhack - Recommendations for a keyboard with bigger tent angle

I’m using kinesis advantage for 7-8 years. However, I get pain in right thumb(because of using thumb clusters I guess) from time to time. Recently I got a chance of using Goldtouch keyboard(for some days) and I liked it a lot.


u/MyGOSHICantBelieveIt (2020-05-20). r/ergodox - My ErgoDox may have given me RSI

As stated - my left thumb now has an intense shooting pain whenever I use my ergo. This might be because the positioning of both space and backspace on the left thumb engages the muscles/joint there so much more than with a regular keyboard (my left thumb was rarely if ever used on a regular keyboard).

u/openstruct (2020-04-29). r/ergodox - Increased wrist/thumb pain

I’ve been using a split keyboard for a few years now and recently switched to an ergodox ~9 months ago. The first few months were great, but now I’m starting to experience wrist/thumb pain and I can’t figure it out. I’m doing all the “right” things: wrist rests, shoulder width spacing, elbows are ~90 degrees, correct touch typing, damn good posture, but still pain. I’ve experimented with tenting but no dice.

Daerid (2014-05-23). geekhack - My year with the ErgoDox (or how I learned to stop worrying and love QWERTY)

A few months ago I started noticing a slight pain in the base of my right thumb, right where it meets the wrist. I didn’t really pay any attention to it at first, but it kept getting worse and worse. It didn’t register to me that it would be related to my keyboard, because “hey, I’m using an ergo board! there is no way!” […] After examining closely how my hands moved and what muscles I was using when typing on the ErgoDox, I realized that it was the placement of the thumb clusters.

Common thumb injuries

The following is a primer on a few common kinds of thumb injuries and the involved anatomy. In-depth references can be found in the links under Further Reading.

The following is informational only. See a doctor for professional medical advice.

Texter’s thumb, aka De Quervain’s tenosynovitis

Outside the niche world of custom ergo keyboards, a common kind of thumb injury is “texter’s thumb,” aka De Quervain’s tenosynovitis, from excessive texting on smart phones. A keyboard with thumb keys appears to pose a similar possibility of injury, since thumb use is comparable.

De Quervain’s tenosynovitis is a condition of inflammation on the thumb side of the wrist, in the sheath around the tendons that go to the thumb (the tendons for the extensor pollicis brevis and abductor pollicis longus muscles).

Tendon sheath for the extensor pollicis brevis and abductor pollicis longus.

De Quervain’s causes pain and swelling at the base of the thumb and thumb side of the wrist. It can make grasping and pinching movements painful and weak. It can become debilitating if untreated and may require surgery.

Thumb pain in carpal tunnel syndrome

Though not specific to the thumb, carpal tunnel syndrome is one of the most common kinds of injuries involving thumb pain. The carpal tunnel is a narrow passageway on the palm side of the wrist formed by the arch-shaped carpal bones and flexor retinaculum connective tissue. The flexor tendons to the fingers and the median nerve pass through the carpal tunnel.

Median nerve passing through the carpal tunnel.

Carpal tunnel syndrome (CTS), also more specifically referred to as Idiopathic Median Neuropathy at the Carpal Tunnel (IMNCT), is a condition where the median nerve is pinched in the carpal tunnel, perhaps because inflammation caused surrounding tissues to swell and decrease the space in the tunnel.

Damage to the median nerve can cause numbness, tingling, and burning sensations in the thumb and other fingers. The pain is usually worse at night. There may also be weakness and clumsiness. Carpal tunnel syndrome can lead to irreversible nerve damage and loss of hand function if untreated.

Ulnar collateral ligament (UCL) injury

Another common thumb injury is tearing the ulnar collateral ligament or UCL, a tissue in the metacarpophalangeal (MCP) joint where the thumb meets the palm.

The ulnar collateral ligament (UCL) and surrounding anatomy.
Close up of the metacarpophalangeal (MCP) joint.

The chronic version of UCL injury is called “gamekeeper’s thumb.” Historically, it was common for game keepers to kill a rabbit by breaking its neck between the thumbs, forefingers, and the ground. A force bending the thumb in the outward (valgus) direction engages the UCL. The stress from performing this practice regularly causes attrition in the UCL and can lead to a chronic injury.

Certainly, breaking a rabbit’s neck takes more force than holding a key. Yet it’s worth mentioning that the UCL is another weak point in thumb anatomy.


Many anecdotes above were at least partially to blame on misfitting between keyboard and the user’s hand size. When shopping for keyboards, you can use Splitkbcompare to make 1:1 prints of many keyboards and test how they fit your hands. (Printing tips: double check the paper type and page orientation, and measure the included centimeter marks to verify that the print scaled correctly.)

Trying my hand on a print of the Lily58.

A few anecdotes warn about certain problematic motions, like those where the thumb has to stretch to reach the key. In my keymap, I think about how often I press each key and avoid putting more than one “high-use” function on each thumb to reduce side-to-side and reaching motions. Instead of holding the thumb keys, I go for layer switches that toggle on tap or by using sticky (one-shot) keys.


It pays to keep a critical eye on ergonomics. Keep those thumbs healthy! 👍 👍

Further reading

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