In the case of a sprain there is trauma to a joint and it involves a ligament. Depending on how bad the injury is, depends on the degree of damage. There is usually swelling, tenderness or pain and it is hard to move the joint. The usual treatment is to Rest the area, use ice initially and compression to prevent swelling. Elevation of the part is helpful while resting. In 48 hours you start alternating hot and cold compresses if there are still symptoms. I add ice to the cold
water I am using for the cold compress and make the hot one as hot as the person tolerates, but don't want to burn them. You use hot for 3 minutes and cold for 1 minutes. This is done 2-3 times per day. Always end on cold. The reason for this is that it moves blood and lymph and helps clean up the debris left in the joint as well as brings in nutrients to help the healing. Very simple and very powerful treatment.
Herbs:
I usually use a mix of herbs in an external oil. When it is a sprain it includes ligament damage and Ruta or Rue is specific for ligament damge in both an oil used externally or the homeopathic taken internally. I don't use Rue internally as a whole herb as it can be toxic. For inflammation and to decrease the bruising faster, you can use Arnica or Saint John's Wort. Some people mix these herbs together and keep it available as a Trauma Oil. Technically Arnica
should not be used on open skin. I use Calendula on open skin wounds usually.
Yes, Comfrey poultices are used externally, but I understand the frozen ground.