- 1 Definition/Description
- 2 Lewis Hunting Reaction
- 3 Application Methods
- 4 Conditions treated
- 5 Pros
- 6 Cons
- 7 Possible Risks/Undesirable Effects
- 8 Resources
Cryotherapy, also known as ice application, is the simplest and oldest way to treat injuries. Its worldwide use spread because of its effectiveness, convenience, low cost and ease of transportation. Ice is believed to control pain by instigating local anaesthesia. It also decreases oedema, nerve conduction velocities, cellular metabolism and local blood flow. The effect of the cryotherapy depends on the method, the duration, temperature of the ice and the depth of the subcutaneous fat. 
Lewis Hunting Reaction
The Lewis hunting reaction or hunting response is a process of alternating vasoconstriction and vasodilation in extremities exposed to cold. The term Lewis reaction is used too, named after Thomas Lewis, who first described the effect in 1930. Vasoconstriction occurs first to reduce heat loss, but also results in strong cooling of the extremities. Approximately five to ten minutes after the start of cold exposure, the blood vessels in the extremities will suddenly vasodilate. This is probably caused by a sudden decrease in the release of neurotransmitters from the sympathetic nerves to the muscular coat of the arteriovenous anastomoses due to local cold. This cold-induced vasodilation increases blood flow and subsequently the temperature of the fingers. A new phase of vasoconstriction follows the vasodilation, after which the process repeats itself.
Vasodilation can be cold induced after initial period of vasoconstriction when cold is maintained for longer than approximately 15 min or when temperature is reduced below 10C.
- Ice Packs : It is most common method of cryotherapy. There are different types of ice used in ice packs. The most common types are ice packs made with cubed, crushed and wetted ice. It was discovered that wetted ice is better to lower surface temperature during treatment and maintaining the lower temperature during recovery. It is also more effective in lowering the intramuscular temperature during treatment.
- Ice Spray : A cooling effect can also be produced by icing spray for a similar effect.
- Immersion : Simple or whirlpool immersion.
- Ice Massage : slow strokes in circular motion for 5-10 mins.
More recently whole body cryotherapy has become popular for athletes, to help aid recover, as well as in persistent pain patients such as rheumatological conditions. More research is needed to understand the effect on the body and its relation to pain.
- Acute soft tissue injuries e.g. ankle sprain, muscular sprain, ligament sprain
- Myofascial trigger points
- Acute swelling
- Post orthopaedic surgery e.g. TKR, ACL reconstruction, arthroscopic shoulder surgery.
- Acute sports injuries
- Pain relief
- Swelling reduction
- Decreased surface temperature
- Effective on a wide range of soft tissue injuries
- Little evidence regarding duration and frequency of treatment to be effective
- Compression has been shown to be more effective post operatively
- In rare cases bradycardia and frostbite symptoms have been observed. 
- Some more advanced cryotherapy devices can reduce range of movement following TKR due to immobilisation of the joint. 
Possible Risks/Undesirable Effects
Inhibit Muscle Function
- Cooling can temporarily Inhibit muscle function with potential for increased risk of injury/re‐injury
- Be cautious when having patients weight bear/undertake complex exercise after icing a lower extremity
Elderly patients with impaired sensation and/or circulation will be more vulnerable to an ice‐burn, therefore consider using less intense icing techniques (e.g., moderately cold ice pack wrapped in an insulating layer(s) of towel/cloth)
- Younger patients with intact sensation and circulation may benefit most from direct immersion of the limb in cold water then progressively adding ice cubes
- Cold gel packs stored in a freezer have a surface temperature below 0°C (32°F) and thus an insulating layer should be used between the cold pack and the patient’s skin
Cryotherapy‐Induced Nerve Injuries
- Most common when cold is applied in combination with compression
- Check capillary refill during application of ice combined with compression therapy to ensure adequate blood flow
Generalized Cooling and Decrease in Core Temperature
- Shivering and piloerection are signs of decrease in core temperature which may compromise patient safety (especially in the elderly and those with fever)
- The application of therapeutic cryotherapy should produce only local effects
Ice may contribute to shortening of collagen fibres in connective tissue
- After gaining ROM by warming, stretching and then strengthening in the newest part of the ROM, it is likely counterproductive to cool the tissue in a shortened position
- If one wishes to cool the tissue post stretch and exercise, it is best to do so with the tissue in a lengthened position
- In patients with significantly restricted ROM due to scar tissue, it may be preferable not to use ice.
Be aware of conditions in which icing is contraindicated
- CRPS, haemoglobinuria, cryoglobulinemia,
- Peripheral vascular disease
- Impaired circulation: Raynaud’s disease
- Hypersensitivity to cold
- Skin anaesthesia
- Bleakley C, McDonough S, MacAuley D. The use of ice in the treatment of acute soft-tissue injury: a systematic review of randomized controlled trials. The American journal of sports medicine. 2004 Jan;32(1):251-61.
- Dykstra JH, Hill HM, Miller MG, Cheatham CC, Michael TJ, Baker RJ. Comparisons of cubed ice, crushed ice, and wetted ice on intramuscular and surface temperature changes. Journal of athletic training. 2009 Mar;44(2):136-41.
- Daanen HA. Finger cold-induced vasodilation: a review. European journal of applied physiology. 2003 Jun 1;89(5):411-26.
- Galiuto L. The use of cryotherapy in acute sports injuries. Annals of Sports Medicine and Research. 2016;3(2):1060.
- Banfi G, Lombardi G, Colombini A, Melegati G. Whole-body cryotherapy in athletes. Sports medicine. 2010 Jun 1;40(6):509-17.
- George Eliot Hospital. Applying an Icepack - Physiotherapy Advice Video Available from: https://www.youtube.com/watch?v=gJOMV2mZ1B0 [last accessed 28/09/2020]
- Ni SH, Jiang WT, Guo L, Jin YH, Jiang TL, Zhao Y, Zhao J. Cryotherapy on postoperative rehabilitation of joint arthroplasty. Knee Surgery, Sports Traumatology, Arthroscopy. 2015 Nov 1;23(11):3354-61.
- Hubbard TJ, Denegar CR. Does cryotherapy improve outcomes with soft tissue injury?. Journal of athletic training. 2004 Jul;39(3):278.
- Thienpont E. Does advanced cryotherapy reduce pain and narcotic consumption after knee arthroplasty?. Clinical Orthopaedics and Related Research®. 2014 Nov 1;472(11):3417-23.
- Prohaska J, Badri T. Cryotherapy. InStatPearls [Internet] 2020 Feb 7. StatPearls Publishing.