MR-IMAGING OF PATELLAR RETINACULAR LIGAMENT INJURIES

Seventeen patients with patellar retinacular ligament injuries were ev aluated with magnetic resonance (MR) imaging. MR findings were correla ted with clinical, surgical, and arthroscopic findings. The injuries i nvolved the medial retinacular ligament in 16 of 17 patients and the m edial and lateral retinacular ligament in one patient. Nine of 17 pati ents showed MR evidence of a patellar dislocation. In these patients, a triad of findings that included focal impaction injuries involving t he lateral femoral condyle, osteochondral injuries of the medial patel lar facet, and injuries of the medial retinacular ligament were seen. Seven of the nine patients with patellar dislocation injuries had fran k osteochondral injuries. The injured retinaculum had an indistinct, i rregular appearance associated with edema and hemorrhage. The patellar dislocations were clinically unsuspected in the initial evaluation of eight of these nine patients. In eight of 17 patients, the mechanism of injury was a patellar tendon tear (n = 1) or valgus hyperextension (n = 7). In the seven patients with hyperextension injuries, three had associated meniscal and cruciate ligament tears. MR imaging can help define patellar retinacular and associated osteochondral injuries, whi ch may be clinically useful information.