Patellar impingement by synovial cord following anterior cruciate ligament reconstruction

We found a cordlike structure (synovial cord) in the patellofemoral joint causing patellar impingement in a 45-year-old man after anterior cruciate ligament (ACL) reconstruction. Arthroscopic examination revealed that a cylindrical cordlike soft tissue with a smooth surface extended between the medial and lateral capsule of the patellofemoral joint. The tissue histologically consisted of dense collagen fibers in parallel bundles covered with thin layers of synovial tissue; in addition, there was a proliferation of small vessel patches surrounded by hemosiderin-laden macrophages, which indicated bleeding episodes due to impingement in the patellofemoral joint. To our knowledge, this is the first case report of a synovial cord in the patellofemoral joint causing patellar impingement following ACL reconstruction.