Abstract
A hypermobile lateral meniscus is difficult to diagnose on MRI because there is no tear or morphological abnormality of the meniscus, and it is usually diagnosed on arthroscopy by reproducing the anterior subluxation of the posterior horn of the lateral meniscus. A case in which CT findings suggested a possibility of hypermobile lateral meniscus is reported. The patient, in her 20s, presented with painful locking symptoms of her left knee. CT in a locked position of the knee joint showed that the posterior horn of the lateral meniscus was anteriorly subluxated. After CT examination, she was able to extend her left knee without treatment. MRI in a neutral position of the knee joint performed 2 days later showed that the lateral meniscus was normal in position and appearance. Based on the CT findings, it was thought that her symptoms could be due to a hypermobile lateral meniscus. Careful observation of the lateral meniscus on CT at the symptomatic state may be useful for diagnosis of hypermobile lateral meniscus.
