D&D Disability – mechanics for basic lower-limb prosthetics

This is part of the series on representing disability in D&D.

In my previous post, I introduced Meurtle to the Domenechs, describing what it might be like getting his first prosthetic consultation (based on descriptions by amputees Jamie Andrews and Harry Parker). Now to turn the story into mechanics.

I have tried to think through appropriate impacts and effects with and without prosthetics, based on descriptions in the references (see end) and application of physics/engineering, but I don’t have personal experience or know anyone who does. So I would welcome people trying these mechanics out and giving feedback, particularly those who know what it is like living with a prosthetic leg (or two).

Like most of this site, these mechanics are licensed under Creative Commons licence CC BY-NC-SA 4.0. They can be freely shared and modified as long as I am attributed, they are not used commercially, and any modifications are shared similarly.

In developing these mechanics, I am trying to remember this statement from The Combat Wheelchair:

Remember: The Combat Wheelchair does not give a disabled character any kind of ‘advantage’ over the able-bodied characters in their party. It merely enables a disabled character to continue adventuring. You should not be punished for something you can’t help. To be punished for having a disability is cruel.

Anyone can be a hero.

Introduction to The Combat Wheelchair by Sara Thompson @mustangsart

Also the following from DnDDisability:

It’s very important to me when creating disability mechanics that nothing is worded in a negative way. I won’t use words like “severity” or “penalty” – we are not and never should be penalized for a disability. Word choice is so important when it comes to disability content…

@DnDDisability on Twitter

Principles

I am trying to work to the following guiding principles in my development:

  • The prosthetics allow disabled adventurers to participate fully in adventures
  • The rules should be simple enough to use at a table without constant referring back to the ruleset
  • More advanced/expensive prosthetics are available which are more durable and/or provide more advanced features
  • These advanced features may be beyond what a normal adventurer can do in some respect, however even advanced prosthetics still have downsides, and the more benefit they give, the more likely they are to be specialised for that benefit and impaired for general use
  • Putting on, taking off, changing or adjusting prosthetics takes time

There certain impacts of disability which are gritty but not necessarily heroic or interesting and may bog down the game, so these will be deferred to optional additional rules. These include the observations at the end of my previous post:

  • In real life, it requires months of training to become accustomed to prosthetics, and the stump is very sensitive to start with.
  • Wearing a prosthetic never gets completely comfortable in a “never think about it” kind of way. It takes time to put it on and take it off, and the tiniest bit of grit in the cup will just grind.
  • Even if everything is perfect, there will be good days and bad days, and if you wear your prosthetic for too long, or jar it, it will hurt and your stump will complain.
  • Even the best prosthetic isn’t as good as a real leg, and there are always tradeoffs. You see the blade runners in the Paralympics, but most prosthetics aren’t like that, and the blades gain springiness at the cost of stability – it’s harder to balance on them. If you haven’t got a blade, then jumping, or even doing things balanced on your prosthetic, will be much harder.

This post considers the impact of missing parts of legs, and some high-quality basic prosthetic legs. Future posts will expand these to include advanced features, adding and removing prosthetics and complications.

Movement types

These rules consider some different ways of moving. Here are mechanics for these.

Crawling

Crawling is half speed and the character is prone (see PHB p182)

Hopping

Hopping reduces base movement speed to 10’

  • You can hop for 5+CON modifier minutes; longer than this risks exhaustion:
  • For every additional minute past this limit, make a Constitution Saving Throw with DC 10 + minutes hopping past the limit or gain a level of exhaustion
  • Resting for half the time they spent hopping resets the hopping time to zero; starting to hop again before finishing the rest continues the count where it left off
  • For dashing, measure in rounds instead of minutes – they can dash for five rounds before risking exhaustion
  • Jumping distances are halved
  • After dashing or jumping, succeed on a Dexterity (Acrobatics) check or fall prone
Photo by Documerica on Unsplash

For example, Meurtle has CON 13 (+1). He can hop for 6 minutes before risking getting exhausted. After the 7th minute, he must make a DC11 CON Saving Throw or gain a level of exhaustion. After the 8th minute, he must make another CON Saving Throw, this time with DC12, and so on.

After hopping for 8 minutes, he needs 4 minutes rest. If he starts hopping again before this, he will need to make a DC13 CON saving throw the next minute. If he gets the full rest, he can hop for another 6 minutes before he needs to start making saving throws.

Moving with crutches

Moving with crutches reduces base movement speed to 10’. Normal movement doesn’t risk exhaustion, but every minute of dashing risks exhaustion in the same way as hopping at normal speed.

Baseline for different leg amputation scenarios

Here is an attempt at mechanics for different scenarios which represent the base state unaided.

Missing foot

It is possible to walk if all you are missing is your foot or part of a foot. You would have enough of a leg that you could use your stump for support without becoming too uneven.

The foot is used to balance, so you would be less stable, and you would probably be slower.

  • Half speed on foot
  • Disadvantage on Dexterity checks made to balance
  • After dashing or jumping, succeed on a Dexterity (Acrobatics) check or fall prone

Missing both feet

Missing both feet is  significantly different from just missing one foot. The foot is used for stability, so without any feet you would be much less stable. The foot and ankle are also used for jumping.

  • Half speed on foot
  • Disadvantage on Dexterity checks made to balance
  • After dashing, automatically fall prone
  • Jumping is not possible
  • Melee attacks have a -2 penalty
  • Armour class is decreased by 1
  • Make a Dexterity (Acrobatics) check when hit with a Critical Hit, or when scoring 5 or lower on a melee attack, falling prone on a failed check

Missing an equal part of both legs

If you are missing an equal part of both legs, at least you are still balanced, so in many ways this is functionally equivalent to just missing both feet above. Your speed will be impacted by the amount of leg you are missing.

  • Missing part of both legs below knee: half speed on foot
  • Missing part of both legs above knee: maximum speed 10’
  • Disadvantage on Dexterity checks made to balance
  • After dashing, automatically fall prone
  • Jumping is not possible
  • Melee attacks have a -2 penalty
  • Armour class is decreased by 1
  • Make a Dexterity (Acrobatics) check when hit with a Critical Hit, or when scoring 5 or lower on a melee attack, falling prone on a failed check

Missing part of one leg

Once you’ve lost a significant portion of your leg, moving around on both legs becomes harder because you are unbalanced (literally) – your legs are different lengths so don’t both naturally meet the ground together (unless you have a similar amount missing from both legs).

  • Movement without some sort of aid is restricted to hopping or crawling (see above)
  • Disadvantage on Dexterity checks made to balance
  • Melee attacks have a -2 penalty
  • Armour class is decreased by 2
  • Make a Dexterity (Acrobatics) check with Disadvantage when hit with a Critical Hit, or when scoring 5 or lower on a melee attack, falling prone on a failed check

Missing unequal parts of both legs

Missing part of one leg is one thing, but without part of both legs you no longer even have a foot to help you balance or jump.

  • Movement without some sort of aid is restricted to crawling, and hence you are automatically prone (see above)
  • Dexterity checks made to balance have a penalty of -10 on the roll.
  • Melee attacks have a -2 penalty
  • Armour class is decreased by 2
  • Make a Dexterity (Acrobatics) check with Disadvantage when hit with a Critical Hit, or when scoring 5 or lower on a melee attack, falling prone on a failed check

Quality prosthetics

The Domenechs produce quality prosthetics which give the best results possible, are durable, and have the least side-effects. A future post will look at the downsides of cheaper models.

Domenech’s Walking Foot

Artificial right leg for amputation below knee, 1851-1920
From the Science Museum

Suitable for: missing foot

Indicative cost: 20gp

Description: a wooden foot with strapping which stretches up the lower leg attaching it securely. Clever springs incorporated into the ankle give a level of natural movement and jumping ability.

Effect: changes the impact of missing feet to:

  • Base speed is reduced by only 5’ from normal
  • Dexterity checks made to balance are normal
  • Jumping taking off from the prosthetic foot has half distance
  • If landing on the prosthetic foot after jumping, succeed on a Dexterity (Acrobatics) check or fall prone

Domenech’s Booted Foot

Suitable for: missing foot

Indicative cost: 30gp+

Description: similar to the walking foot, but the strapping is incorporated into a fine leather boot; comes with matching boot for the other leg.

Domenech’s Peg Leg

Pin leg, for below-knee amputation, probably English, 1900-1930
From the Science Museum

Below Knee

Suitable for: missing leg below knee

Indicative cost: 30gp

Description: a beautiful turned and polished wooden pole attached to a shaped leather socket for the stump, with a laced leather wrapping attached to the socket with three leather straps which go either side of and behind the knee; this laced wrapping grips the thigh. Can have an additional strap which goes over the shoulder for additional security.

Above Knee (Leather Socket)

Artificial leg (probably above-knee)
From the Science Museum

Suitable for: missing leg above knee

Indicative cost: 25gp

Description: a beautiful turned and polished wooden pole attached to a shaped leather socket, with a laced upper section which helps it grip the thigh above the stump. Can have an additional strap which goes over the shoulder for additional security.

Above Knee (Wooden Socket)

Wooden leg for amputation above knee, 1861-1920
From the Science Museum

Suitable for: missing leg above knee

Indicative cost: 35gp

Description: a beautiful turned and polished wooden pole attached to a shaped wooden socket. Can have an additional strap which goes over the shoulder for additional security.

Effect (Below and Above Knee)

Effect (single): changes the impact of a missing leg (below or above knee) to:

  • Half speed on foot
  • Disadvantage on Dexterity checks made to balance
  • After dashing or jumping, succeed on a Dexterity (Acrobatics) check or fall prone

Effect (pair): changes the impact of two missing legs (below or above knee) to:

  • Half speed on foot
  • Disadvantage on Dexterity checks made to balance
  • After dashing, automatically fall prone
  • Jumping is not possible
  • Melee attacks have a -2 penalty
  • Armour class is decreased by 1
  • Make a Dexterity (Acrobatics) check when hit with a Critical Hit, or when scoring 5 or lower on a melee attack, falling prone on a failed check

Domenech’s Walking Leg (Below Knee)

Suitable for: missing leg below knee

Indicative cost: 40gp

Description: a shaped wooden foot and calf culminating in a shaped socket for the stump, with a laced leather wrapping attached to the socket with three leather straps which go either side of and behind the knee; this laced wrapping grips the thigh to for extra security. Clever springs incorporated into the ankle give a level of natural movement and jumping ability. Can have an additional strap which goes over the shoulder for additional security.

Effect: changes the impact of a single missing leg (below knee) to:

  • Base speed is reduced by only 5’ from normal
  • Dexterity checks made to balance are normal
  • Jumping taking off from the prosthetic foot has half distance
  • If landing on the prosthetic foot after jumping, succeed on a Dexterity (Acrobatics) check or fall prone

Domenech’s Walking Leg (Above Knee)

Artificial leg for amputation above left knee, 1901-1919
From the Science Museum

Suitable for: missing leg above knee

Indicative cost: 50gp

Description: shaped wooden foot, calf, knee and lower thigh, culminating in a shaped socket, with a laced upper section which helps it grip the thigh above the stump. Has a hinge in the knee which can be released to fold when sitting, or can be locked straight for walking. Can have an additional strap which goes over the shoulder for additional security.

Effect (single): changes the impact of a single missing leg (above knee) to:

  • Base speed is reduced by 5’ from normal
  • Dexterity checks made to balance are normal
  • Jumping taking off from the prosthetic foot has half distance
  • If landing on the prosthetic foot after jumping, succeed on a Dexterity (Acrobatics) check or fall prone

Effect (pair): changes the impact of two missing legs (above knee) to:

  • Base speed is reduced by 5’ from normal
  • Disadvantage on Dexterity checks made to balance
  • Jumping has half distance
  • After dashing or jumping, succeed on a Dexterity (Acrobatics) check or fall prone

Notes

As I said at the top, I have tried to think through appropriate impacts and effects with and without prosthetics based on descriptions in the references and application of physics/engineering, but I don’t have personal experience or know anyone who does. So I would welcome people trying these mechanics out, particularly those who know what it is like living with a prosthetic leg, and giving feedback. You can get in touch in replies to this post, by Twitter to @Melestrua, or email to Melestrua@melestrua.net

References

Key reading which has informed this:

  • Jamie Andrew’s “Life and Limb” (as mentioned above). Jamie lost part of both arms and legs to frostbite in a storm when mountain climbing.
  • Harry Parker’s “Hybrid Humans”. Harry is a former soldier who lost part of his leg to an IED in Afghanistan. He looks into both the history and the latest advances in robotics, tech and implants, and also talks about the impact on his life. It was his description of the Cybathlon at a trade show which brought home to me how underwhelming even the most advanced prosthetics are compared to real legs (see pp107-108 in the chapter “Freedom is expensive”).
  • Artificial Parts, Practical Lives, Modern Histories of Prosthetics. A collection of essays examining different aspects of prosthetics through history.
  • The Body Factory. A graphic novel where a guy who has part of his arm amputated after a motorbike accident is taken through the history and future of prosthetics by Ambrose Paré, the French barber-surgeon who revolutionlised the art of amputation.
  • The Cormoran Strike series. Cormoran is a former solider who lost part of his leg in Afghanistan, and the author has done a lot of research talking to similar veterans to make his life with a prosthetic realistic. He is always pushing beyond what is sensible for his leg, and then having to live with the dull ache and aftermath.
  • The Science Museum website

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