Background Acute lateral ankle sprains (LAS) can lead to chronic injury if treated improperly. Therapeutic modalities such as deep oscillation therapy may enhance patient outcomes.

Objective To determine the effect of a single-session of deep oscillation therapy for an acute LAS compared to the standard of care.

Design Randomised controlled trial.

Setting Athletic training clinic.

Participants Thirty-eight active individuals (age = 20.21 ± 1.54 years; height = 176.20 ± 12.67 cm; body mass = 74.25 ± 14.54 kg; 22 females, 16 males) diagnosed with a Grade I or II LAS, within 48 h of injury participated. Thirty-seven participants completed the study; one participant was excluded.

Interventions Participants were randomly assigned to one of two groups. Group one received the standard of care (SC) for acute LAS (compression, elevation, and cryotherapy for 20 min) and a treatment of deep oscillation therapy (frequency = 150–65 Hz; 1:1 pulse to pause time) for 20 min. Group two received the same treatment as group one, however with placebo deep oscillation therapy.

Main outcome measurements Pre- and post-assessment measures included range of motion (ROM) in plantar flexion, dorsiflexion, inversion, and eversion (degrees), self-reported pain scores using the Numerical Pain Rating Scale (points) and limb swelling with water volumetry (mL).

Results Improvements in ROM were found in plantar flexion  (p = 0.041; mean increase = 2.11), dorsiflexion (p = 0.013; mean increase = 1.89) and inversion (p = 0.051; mean increase = 1.67) yet no interaction effect between groups (plantar flexion p = 0.311; dorsiflexion p = 0.224; inversion p = 0.663; eversion p = 0.123). Both treatments had significant decreases in pain scores (p ≤ 0.00, mean difference = 9.8), however no interaction effect between groups (p = 0.457). Significant differences in limb volume were found (p = 0.001, mean difference = 18.5 mL) for both treatments however no interaction effect between groups (p = 0.863).

Conclusions A single session of deep oscillation therapy does not improve acute outcomes above those observed with SC.