Always wrap a light weight towel or use a clothing barrier between you and the cold pack. Ice should NOT be used directly on the skin.  You can use crushed ice in a ziplock bag, or a gel ice pack, even a bag of peas.  Since inflammation often accompanies joint dysfunction, ice should be applied for 6 minutes when using hard ice, or 12 minutes if using a gel ice pack.  Ice helps to reduce inflammation and numbs the pain when used in short spurts like 12 minutes at a time.  Repeat its application 3-4 times with a 45 minute rest period in between applications of cold.