A prospective randomized trial was performed to compare conservative functional treatment and operative functional treatment for rupture of the lateral ankle ligament. On the basis of the results observed 1 and 2 years after injury, primary functional therapy with a orthetic support appeared to be the method of choice. In a 100-point clinical check-up scale we were not able to find any statistical differences between the treatments. This type of conservative treatment gives a high degree of mechanical stability, a shorter time off work and the ability to take a full, active part in sports within 3 months in all cases. Operative treatment is indicated only in cases of dislocation of the foot and ankle, ankle ligament rupture with additional osteochondral talus fracture, and second-stage injuries or reruptures.