Diets high in processed foods, sweets, sugars, baked breads, chips, cookies and pastries all promote inflammation which promotes arthritis. A menu too high in omega-6 fatty acids (soy, safflower, sunflower, corn oils), and trans-fats (hydrogenated and partially hydrogenated fats) also promote inflammation. Furthermore, diets like the above tend to be too high in calories, upset blood sugar balance and lead to weight gain. Being overweight greatly increases the stress on the low back, hip and knee joints.
Conversely, diets high in relatively unprocessed, low-temperature-cooked (even raw) foods rich in omega-3 fatty acids (chia and flaxseed, walnuts, fatty fish, grass fed meats) and high antioxidant foods (fruits, vegetables, beans, herbs, spices and tea) are anti-inflammatory.
There are other nutrients that may promote joint health. Glucosamine and chondroitin are well-known. Gelatin, MSM (a naturally occurring sulfur compound in our diets), vitamin D, folic acid and B12 may play a role as well.
My favorite medical food shake for joint inflammation is UltraInflamX 360 by Metagenics.