Arthritis is actually not a single disease but a group of medical conditions that primarily affect the joints in the body. There are several types of arthritis, and each type has different causes. Osteoarthritis is probably the most common type of arthritis, and it is often simply related to aging, but can also be caused by infections or by injuries. Rheumatoid arthritis is also fairly common, and this type of arthritis is an autoimmune disease, in which the immune system itself attacks the joints. You have not mentioned which type of arthritis you are suffering from, but there are some common factors in the treatment for all types of arthritis.
A salt water bath is sometimes recommended for arthritis; the treatment is supposed to provide some amount of relief from the pain. Rubbing the salt on your body is not quite the same thing — ideally, you should soak yourself in warm salt water for ten to fifteen minutes. Instead of sea salt, you can also use Epsom salts. However, this is only a minor part of the treatment, and hopefully you are simultaneously taking other measures as well. These include exercising regularly, modifying your diet, and losing weight if necessary.
answered by G M