Surgical management of a double-layered patella: a case report.

The double-layered patella (DLP) is a rare intra-articular disorder that in most cases is associated with multiple epiphyseal dysplasia (MED). The DLP usually consists of an anterior and a posterior layer with a cartilaginous interface between the two parts. In this article, we present a case of bilateral DLP of a 17-year-old female adolescent with MED, suffering clinical symptoms on her left knee. Upon clinical examination, a painful "snapping" of the patella at 30-40 degrees flexion of the left knee was evident and two osseous layers could be identified in standard radiographs. Arthroscopic examination revealed a transient cranial displacement of the posterior osteochondral layer at 30-40 degrees knee flexion that replaced beyond 40 degrees knee flexion with a visible jump. Surgical management in this case of DLP comprised open debridement of the soft tissue interface and fusion of the two osseous layers using double-threaded screws leading to an excellent outcome at 12 months follow-up.