60 patients, aged 18-40 years, presenting with an isolated, unilateral, acute unstable inversion ankle sprain will be included in this bicentric, biphasic, randomized controlled trial. Patients will be randomized by envelope drawing. All patients will be allowed early mobilization and pain-depending weight bearing, limited functional immobilization by orthesis, PRICE, NSARDs as well as home and supervised physiotherapy. Supervised physical therapy will take place twice a week, 30 minutes per session, for 6 weeks, following a standardized intervention protocol. During supervised physical therapy, the intervention group will perform similar exercises on a side-alternating sinusoidal vibration platform as the control group. Two time dependent primary outcome parameters will be assessed. Short-term outcome after six weeks will be postural control quantified by the sway index. Mid-term outcome after one year will be assessed by subjective instability, defined by the presence of giving-way attacks. Secondary outcome parameters include return to pre-injury level of activities, residual pain, recurrence, objective instability, energy / coordination, Foot and Ankle Disability Index and EQ 5D.