Displacement of the posterior horn of the lateral meniscus into posterolateral compartment: an unusual injury pattern.

We report a case of acute ACL injury with an unusual lateral meniscal tear pattern. The entire posterior horn of the lateral meniscus was avulsed from its attachments while remaining in continuity with the body of the meniscus. It was displaced posteriorly and laterally to the popliteus tendon so that it was not immediately visible at the time of arthroscopy. This type of displacement of the posterior horn of the lateral meniscus is difficult to identify at arthroscopy and has not previously been described in the literature to our knowledge. We recommend to surgeons who encounter an absent posterior horn of the lateral meniscus to consider this injury pattern.