Comparison of bone contusion seen by MRI in partial and complete tears of the anterior cruciate ligament.

OBJECTIVE: Bone contusions are frequently found in association with complete tears of the anterior cruciate ligament (ACL) and can be a helpful secondary sign in diagnosis. We compare the frequency, location, and significance of bone contusions in complete and partial ACL tears.

MATERIALS AND METHODS: Twenty-nine patients with complete and 42 patients with incomplete tears of the ACL were examined by MRI for the presence of accompanying bone contusions within 1 month of injury.

RESULTS: Bone contusions were found in 72% of the complete ACL tears but in only 12% of the partial tears. Of the partial ACL tears with accompanying contusions, 80% were high grade injuries that eventually went on to complete rupture within 6 months. Only 16% of the partial ACL injuries without bone contusion progressed to complete rupture at 1-2 year follow-up. There was no difference between the bone contusions of partial and complete tears in terms of general appearance and location. They were predominantly in the lateral compartment (90%) and had a specific predilection for the mid portion of the lateral femoral condyle and the posterior portion of the lateral tibial plateau, often occurring in tandem.

CONCLUSION: Bone contusions occur with much less frequency in partial ACL tears than in complete tears but their presence in partial rupture favors a high grade tear that is likely to become complete.