I enjoy carving with a knife, but my hand begins to hurt after a while.
Carving with a knife can put stress on the wrist and will often aggravate arthritis and other conditions.  There are a few things you may wish to try.
First is adding a wrist brace that reduces the stress on your wrist.

Increasing the size of the knife handle will often provide some relief; this can be done by wrapping the handle in Vetrap or having a larger handle made.

Finally, your knives should be professionally sharpened, this reduces the force required to carve.
Knife Questions & Answers
Why are there so many different knives?
Knives perform varied tasks depending upon their shape and size.
Blade thickness varies depending on the wood to be carved and expected use.
Straight edged knives are used for most carving.

Up-turned cutting edge blades are used for recessed cuts.
What is the best carving knife?
Most knives are good quality but there is no one knife that everyone likes.
What steels are used in carving knives?

Most of these make excellent knives
I use O1 or W1 because of the low temperature requirements for heat treating.
What is the best handle shape?
I find the one that fits my hand has the best shape. (but seriously)
Try to avoid handles that are designed for one person or one cutting position.
I want to make my own handle; what material should I use?
Most hardwoods make good handles; but there are things to be cautious of.

Woods that contain much oil may not bond well with the blade.
Wood that is not sound may break away from the blade during use.
Some woods may cause an undesired skin reaction with continued use.

A good guide is to use common hardwoods such as Walnut, Cherry, Maple, Oak, Apple, etc.
I like Rhododendron, Holly, Plum, Apple and others; but do not like Sycamore, Mahogany, Black wood, or Ebony for knife handles.

What should I look for in a pocket knife for whittling?
What determines the best length blade for carving?
How many knives does a carver need?
The popular opinion is three; Roughing, Carving, and Detail. (Don't tell my wife)
What is a "Stab" knife used for?
As the name implies, it is used in a stabbing motion to emphasize and highlight certain areas of a chip carving.
What is the difference between a roughing, carving, and detail knife?
Do carving knives come ready to use?
How many knives do I need for Chip carving?

Two; a chip and a stab knife
Thin, locking blades, Good steel, Comfortable handle, Light weight
Most carving knives are not sold ready to use. 
Knife manufacturers only have time to put on a "Factory Edge."
Custom or hand made knives are (normally) sold ready to carve with.
Tool suppliers will usually sharpen the tools they sell; if requested at the time of purchase.
The best blade length is determined by two things; experience and what is being carved.
New carvers should start with a blade around 1-1/2".
More experienced carvers often prefer longer blades.

If you are carving "Pencil people" your knife will be quite short; but if you were carving a life-size decoy, it would require a long blade.
Most roughing knives have thicker and longer blades; and are used to remove large amounts of wood quickly without breaking the blade.

Detail knives have short thin blades for carving delicate details.

Carving knives do everything between those two extremes.
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What is the difference between a "Factory Bench Knife", a "Handmade Knife", and a "Custom Made Knife"?
A factory bench knife is a standard design originating in Europe; most are serviceable knives.  The bench knife has a small, straight handle with a straight cutting edge.  The blade length will normally be 1-1/2 inch to 1-3/4 inches long.

Handmade knives (most often) are made entirely by hand by a small company or a one-man operation.  The variety of blade shapes and styles cover most carving situations you may be faced with.  Handles are standardized by the knifemaker, as is the blade grind and finish.

Custom knives vary by the amount of customizing that goes into them.
Most often you will choose the handle and blade style, and perhaps the wood for the handle.
In rare instances, you have a say on all features of the knife.  This will include blade length, shape, grind, and perhaps even the steel that it will be made from.   The handle shape, wood type, color, and finish may also be specified.  Finally, a knife that is truely custom made for you will require hand measurements to insure a perfect fit.
If a person is missing fingers and cannot use a standard knife, can anything be done?
Yes, knives may be altered to compensate for missing fingers.  This is most common on custom made knives, but may be possible on handmade knives depending upon the knifemaker.
How are knife blades attached to the handles?
Handles are normally attached with rivets or epoxy, occasionally both are used.
Is the entire blade the same hardness?
On most small blades the answer is yes.  Larger blades such as roughout knives may be "edge quenched", this makes a superior knife for heavy work.
The edge is quenched first, or occasionally only the edge is quenched.
This process imparts more toughness to the remainder of the blade.
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