Our bodies need water, at least 50 ounces a day.  Staying hydrated is very beneficial for joints and muscles.  It helps your body maintain the proper blood volume and allows nutrients to move through your body and into your joints.  Joints are like hinges that are connected by ligaments and coated with cartilage to keep the bones from rubbing together. Plenty of fluids keeps your joints and cartilage cushioned and lubricated, and keeps waste moving through your body.  If your body has enough fluid then your joints have the cushioning and nourishment that they need.