The double ACL sign: an unusual bucket-handle tear of medial meniscus.

Several characteristic magnetic resonance imaging (MRI) signs of meniscal bucket-handle tears are well known and widely used. This case report presents a new MRI sign of a meniscal bucket-handle tear. A 17-year-old boy visited our hospital because of the pain in his left knee. Preoperative MRI on sagittal view showed a tear in the anterior horn of the medial meniscus and a displaced fragment of the medial meniscus in front of the original anterior cruciate ligament (ACL), which looks like another ACL. Under arthroscopic examination, the bucket-handle medial meniscus displaced parallel to the ACL was observed. A longitudinal tear was extended from the anterior horn to the posterior horn of medial meniscus. To our knowledge, this new MRI sign of bucket-handle tear, "the double ACL sign", has not been previously reported. Level of evidence V.