You have an insect, not a disease, that is spread by eggs in the soil. It is unlikely that you would be able to get all of the eggs by removing the soil. Solarizing the the soil has been somewhat, temporarily, helpful.
The best method of control is a good, healthy soil that supports predators of the Root Knot Nematode. There is also much evidence that planting certain members of the Matigold family can help control them.
Perhaps this link will be of some help.

Here is a link that might be useful: Root Knot Nematodes

Thanks kimmsr. What are the chances over the next 10 or 20 years that the Nematodes would spread to my other fruit trees if I do not actively spread them through tools and do not disturb the contaminated dirt around the fig?

I've worked incredibly hard over the last 10yrs experimenting with different kinds of fruit that will be successful in my high desert climate. Of these I've searched far and wide to acquire and plant the perfect cultivars of apricots, pomegranates, and jujubes. I've put up cedar log windbreaks, a rainwater catchment, etc.etc I want my grand kids to be able to enjoy the 'fruit' of my labor. What am I really looking at here? How contagious is it? I don't want this to spread and have to continually battle this pest with more time, money, and work, or have sickly, unproductive fruit trees the rest of my life! ugh! Now that I've introduced nematodes through a potted plant(don't remember the nursery now)do I need to consider scraping it all and moving?!

The key to limiting nematodes in the garden is to NOT move SOIL or PLANTS from the infested area, or near it, to other parts of the garden.

Give up your dreams of getting rid of the nematodes.
Won't happen unless you move to a nema-free site.

Instead, focus on the plants that will grow successfully in spite of them. Likely your county's Extension Service office has helpful info for you. Locate your office here: http://www.csrees.usda.gov/Extension/

Know that certain marigolds can *only* reduce RKN populations if planted in a solid stand for an entire season and without the RKN host plant in the area.

Jean,
who gardened successfully (including figs) in SoCal for 30-some years in spite of RKN

Here is a link that might be useful: locate your county's Extension Service office

Jean,
Thanks for sharing your knowledge and experience with me. I think I'll just start growing figs in containers. I had already dug up a fig tree about 5 ft from the contaminated one last week because it wouldn't fruit for me. Today upon closer inspection revealed that part of its roots - on the side next to my contaminated tree had the root knots on it. I refilled the hole this afternoon with the pile of dirt I created when I had dug it, and the angle of the sunlight illuminated that I was stirring up the dirt in the air as I worked.
Now I'm paranoid everything in a 20 ft radius will get the RKN and that my very footsteps are spreading the nematode eggs. Is it THAT contagious, or am I just being OCD?

Kimmsr, nematodes are not related to insects in any way. They are not even arthropods.

cstair, I am not sure that 'contagious' is the right word for these very small round worms. They do certainly spread, slowly but surely, and there isn't much you can do about it. They move through the soil on their own, and we certainly assist in their spread many of our gardening activities.

I would avoid RKN susceptible plants like crazy and try to find out what you can grow that is reported to be resistant to the damage.

Your local extension office might have some pertinent information regarding these nematodes.

Thanks rhizo. This is kind of the straw. I'm thinking of selling my house, moving to married housing, and getting my masters. I can take cuttings of my rare poms, and in a few years move south to a better climate for my poms, figs, jujubes, and plant olives as well. What kills the eggs so I can be sure to disinfect my cuttings? I feel like I need a hazmat suit.