You can avoid a lot of joint problems by getting a good mix of saturated fats from animals (and plants) and monounsaturated fats from plants and minimizing your intake of omega 6 fats. The aim is a 1:1 ratio of omega 6 fats to omega 3 fats, but realistically, a 2:1 ratio O6:O3 is easier to achieve. Just avoid at all costs the typical vegetable oils like soy, safflower, canola, peanut etc. The consumption of healthy oils and fats reduces inflammation not just in your joints but throughout your body and in fact, NSAID pain relievers also do the same thing. This is why pain relievers help the symptoms of arthritis! But you can prevent it altogether by just eating healthy fats to begin with. I didn't even know this would be an outcome of eating this way, but one day I realized I had no more beginning arthritis and no more pains in my feet and someone told me it was because of the fats.
Other than that, arthritis is also an auto-immune issue and eating this way will minimize the propensity to develop auto-immune problems by minimizing foods that open little cracks in your intestines to let foreign proteins in. Those foods tend to be wheat and gluten and a few other things. If you are too far gone already, you might have to avoid tomatoes and white potatoes, peppers and other plants in the nightshade family.
So eat lots of nutrient-dense foods that Mark lists in his blog pages and book and you should do just fine.