Ankle sprain is a common condition in the general population, with a prevalence of 11.88%, and an incidence of seven sprains per 1000 exposures in athletes, resulting in a high frequency of chronic ankle instability. Therefore, effective therapies are increasingly sought after by clinicians. Cryotherapy is a low-cost and easy-to-use treatment option, being considered a potentially effective therapy in the acute inflammatory phase due to preclinical research findings, which suggest that cryotherapy can control inflammatory processes and promote local analgesia by decreasing nerve conduction velocity, which could lead to improved clinical outcomes. However, the current literature lacks evidence on clinical outcomes to support its use, raising the importance of new randomized controlled trials with low risk of bias and appropriate comparator groups.

The aim of this not applied study protocol is to investigate the effectiveness of cryotherapy on function, pain intensity, swelling, and dorsiflexion range of motion in people with an acute episode of ankle sprain.

This is a two-arm prospective randomized controlled trial protocol, designed according to the SPIRIT guideline. People over 18 years old with a clinical diagnosis of grade I or II ankle sprain, and time of up to 72 hours from the injury episode, will be randomly allocated in the Ice Group, which consists of home medical prescription of immersion of the ankle in an ice bucket or, secondarily, ice packs, combined with elevation and non-steroidal anti-inflammatory drugs or to the No-Ice Group, which consists of the same medical prescription as the experimental group, but with no ice included. Our primary outcome is function, as measured by the Lower Extremity Functional Scale (LEFS). Our secondary endpoints are pain intensity (Numeric Pain Scale, 0-10), swelling (figure-of-eight method), and dorsiflexion range of motion (goniometry). Follow-ups will be performed at post-treatment (7 to 14 days) and 12 weeks after allocation. A sample size of 82 participants will be required for a minimum detection of the estimated 9-point effect size of the primary endpoint, with a power of 80%, a power of 5%, and an expected dropout rate of 20%. Statistical analysis will be performed following the intention-to-treat principle. Data normality will be tested by the Kolmogorov-Smirnov test. Parametric data will be analysed with mixed effects models for repeated measures with post-hoc Bonferroni analysis, and in case of non-parametric data, with generalized linear models of mixed effects. Effect sizes will be interpreted based on their minimal clinically important differences.

The results of this study may help to clarify the effects of cryotherapy in the treatment of acute ankle sprains and may guide clinicians in making better decisions.