Observation of anomalous insertion of the medial meniscus on the anterior cruciate ligament. 
We wanted to determine the frequency of occurrence and types of anomalous insertions of the medial meniscus to the anterior cruciate ligament (ACL) in Finnish patients.  In 987 consecutive arthroscopies from January 1996 to August 1998, the meniscal pathology was mapped using videoprints and drawings.  We found 11 anomalous medial meniscus insertions to the ACL.  There were 4 female and 6 male patients in the series.  In 1 woman, the anomaly was bilateral.  The mean age of the patients was 30.6 years (range 14 to 63 years).  The anomalous band was excised in all patients.  The anomaly usually was not the finding that caused the need for arthroscopy.  In 3 knees, the anomaly was the only pathologic finding.  The frequency of this anomaly occurring was approximately 1.2%.  The anomalous medial meniscus insertion to the ACL is a very rare clinical finding.  Arthroscopic surgeons should be aware of its existence as well as of other anterior horn insertion variations of the medial meniscus.