'Cryo' means 'cold'.
Techniques of icing
The image shows a cryotherapy unit, where the container holds iced water which circulates around the knee joint.
You can also simply misten a towel and wrap it around some ice from the refrigerator. Remember that ice from the freezer is FAR colder than from the refrigerator so if you use freezer ice you need to crush it and use a good thick towel. Better is a bag of frozen peas. Ice the limb for about 15 minutes only. Repeat as needed but don't leave the ice on so long that the skin burns!