Ankle injuries represent one of the most commonly occurring musculoskeletal complaints. The vast majority of such injuries occur as a result of inversion trauma with the foot in some degree of plantar flexion and involve damage to the lateral structures of the ankle. Sprains of the lateral ankle ligaments are associated with significant costs  and account for an estimated 302,000 annual admissions to Accident & Emergency (A&E) Departments in the UK .
In addition to the immediate onset of pain, swelling and loss of joint motion, it has been reported that in 15 – 73% of cases, chronic ankle instability (CAI) with recurrent sprains and residual sensations of giving way may occur following lateral ankle sprain [3, 4]. However, the precise etiology of CAI is unclear and as a consequence the optimal intervention for the management of acute ankle sprain is controversial. While a significant body of evidence supports the use of early functional treatment [5–7], there is little high quality research evidence to suggest which interventions best augment this treatment approach. Clinicians therefore continue to treat such injuries pragmatically, with current recommendations ranging from no intervention to physiotherapy referral, prophylactic bracing, or cast immobilisation [8–11].
Cryotherapy (the application of ice for therapeutic purposes) is a common treatment modality employed in the management of acute soft tissue injuries. Despite its widespread clinical use, the precise physiological responses to ice application have not been fully elucidated. Moreover, the rationale for its use at different stages of recovery is quite distinct. In the acute inflammatory phase after soft tissue injury, cryotherapy is thought to decrease oedema formation via induced vasoconstriction, and reduce secondary hypoxic damage by lowering the metabolic demand of injured tissues [12, 13]. Cooling skin surface temperature to below approximately 15°C is also thought to exert a localised analgesic effect by inhibiting nerve conduction velocity [14, 15]. Short periods of ice application have been used during the later, sub-acute phase of inflammation to produce a similar analgesic effect, thus facilitating earlier and more aggressive therapeutic exercise after muscle injury [16, 17]. This combined use of cryotherapy and exercise has previously been termed cryokinetics . Recent evidence has suggested that the addition of exercise to ice application is more effective than ice application alone after various soft tissue injuries, including acute ankle sprain . However, by reducing the conduction velocity of other, non-nociceptive fibres, cold application may also have a number of deleterious effects, including reduced muscle torque . This is of particular relevance if ice is to be applied in combination with therapeutic exercise in the early stages after an acute soft tissue injury. Such effects could lead to the development of altered neuromuscular control patterns and potentially, to an increased risk of re-injury. Conversely, other evidence has shown that ice application does not negatively affect myotatic reflex activity , joint position sense , plantar flexion torque  or more functional measures of agility [24, 25]. Such conflicting findings may relate to the marked variation in cryotherapy protocols described in the literature, particularly in relation to the site, mode and duration of ice application. These factors, in addition to the level of subcutaneous fat, dictate the degree of superficial and deep tissue cooling, and therefore have a direct effect on the subsequent physiological response to cryotherapy .
Evidence from a large-scale systematic review suggested that intermittent ice applications of 10 minutes are most effective at reducing tissue temperature in both injured animal and healthy human models . Such ice applications have been shown to reduce skin temperature to 5°C immediately after treatment . A recent study by our research group also found that intermittent ice applications are more effective than continuous ice at reducing pain on activity after ankle sprain .
Given these findings, it seems a logical progression to examine if the analgesic effects of intermittent ice application can facilitate earlier therapeutic exercise, and subsequently improve clinical outcome following acute ankle sprain. The safety and effectiveness of incorporating therapeutic exercise with periods of intermittent ice application has not previously been examined in patients with acute soft tissue injury. The primary aim of the forthcoming trial is therefore to compare the effectiveness of standard intermittent versus cryokinetic ice applications in the management of acute grade I and grade II ankle sprains. In this manner we hope to contribute further to the existing evidence base in the area of acute soft tissue injury management.