The following was published by the National Safety Council in their July 2017 NSC Instructor Insider Newsletter and provides good advice when treating bone, joint and muscle injuries.
Ice and Injuries; How and How Long?
You already know that first aid guidelines include applying ice to an injured body part, such as a bone, joint or muscle injury. However, what type of ice is best? And how long should ice be applied? Here are some facts to remember when applying ice to an injury:
Ice from frozen water is best: Several studies show that crushed ice, shaved ice and ice cubes are the most effective at cooling the body. Instant ice packs are not as effective at cooling the body, and often do not last as long.
Be careful with instant ice packs: The temperature of instant ice packs, which become cold via a chemical reaction, can vary greatly. Some instant ice packs can become too cold initially, which can damage the skin. Others may not become cold enough, or stay cold long enough to have a meaningful effect on an injury.
Use a wet barrier: If a barrier is used between the skin and ice, it should be wet. This helps the cold application penetrate deeper into body tissue.
Do not ice continuously: NSC First Aid programs recommend icing an injured body part for 20 minutes (or 10 minutes if it produces discomfort), remove for 30 minutes, then reapply. The "more is better" approach should not be used when icing an injury. Continuous icing can potentially cause tissue and nerve damage, and some studies show that it may actually have the reverse effect by increasing swelling.