Empty Sunrise Sign: An Arthroscopic Finding in Recurrent Patellar Dislocation.

Patellar dislocation is a relatively common knee injury and can be challenging to diagnose. We describe an arthroscopic finding we noted in recurrent patellar dislocation. Arthroscopic photos were evaluated from 50 knees with a history patellar dislocation and 100 control patients. We quantified the amount of patellar subluxation seen on a single arthroscopic view and coined it Empty Sunrise Sign if the patella did not overlap the trochlea. Empty Sunrise Sign was found in 82% of 50 cases with recurrent patellar dislocation and none of the 100 control cases. The finding was 100% specific for identifying a recurrent patellar dislocator. High interobserver agreement was noted. Empty Sunrise Sign suggests significant capsular laxity. This may need to be considered in the surgical treatment of recurrent patellar dislocation. Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.