Irreducible lateral dislocation of patella due to an intact retinaculum.

Lateral dislocation of the patella is a common injury that can be treated successfully nonoperatively. The authors present a patient with lateral dislocation of the patella in which the patella rotated 90 degrees about its vertical axis. The retinaculum had been avulsed from the anterior aspect of the patella but was otherwise intact. Because the intact retinaculum prohibited closed reduction, open reduction was performed. The patient has returned to full, unrestricted activities.