Osseous injury associated with acute tears of the anterior cruciate ligament

Multiplanar spin-echo magnetic resonance imaging was performed on 54 patients with acute complete anterior cruciate ligament tears. Imaging was done within 45 days of index anterior cruciate ligament injury. Spin- echo T1- and T2-weighted images were used to deter mine the lesion morphology and location. Only the T2- weighted sagittal images were used for the incidence assessment; T2-weighted spin-echo imaging reflects free water shifts and best indicates the acute edema and inflammatory changes from injury. Eighty-three percent (45 of 54) of the knees had an osseous contusion directly over the lateral femoral con dyle terminal sulcus. The lesion was highly variable in size and imaging intensity; however, the most intense signal was always contiguous with the subchondral plate. Posterolateral joint injury was seen in 96% (43 of 45) of the knees that had a terminal sulcus osseous lesion determined by magnetic resonance imaging. This posterolateral lesion involves a spectrum of injury, in cluding both soft tissue (popliteus-arcuate capsuloliga mentous complex) and hard tissue (posterolateral tibial plateau) injuries. The consistent location of the osseous and soft tissue injuries underscores a necessary similar mechanism of injury associated with these acute anterior cruciate ligament tears. Based on these characteristic findings, several proposed mechanisms of injury are discussed.