Bone Bruise Sign - Orthopaedia

Location	Knee
Diagnosis	ACL tear
Discussion	Sagittal T2 weighted and proton density images which reveal complete tear of the ACL with mild increase in marrow signal in the adjacent osseous structures. The bone bruises, as evidenced by increased signal within the marrow, is likely caused by anterior subluxation of the tibia at the time of tear of the ACL accompanied by impaction of the middle portion of the lateral femoral condyle against the posterior portion of the lateral tibial plateau. Signal intensity abnormalities are probably secondary to edema, hemorrhage, and microfracture.
Reference	Gentili A, Seeger LL, Yao L, Do HM: Anterior cruciate ligament tear: indirect signs at MR imaging. Radiology 1994 Dec;193(3):835-40. Graf BK, Cook DA, De Smet AA, Keene JS: Bone bruises on magnetic resonance imaging evaluation of anterior cruciate ligament injuries. Am J Sports Med 1993 Mar-Apr;21(2):220-3. Murphy BJ, Smith RL, Uribe JW, Janecki CJ, Hechtman KS, Mangasarian RA: Bone signal abnormalities in the posterolateral tibia and lateral femoral condyle in complete tears of the anterior cruciate ligament: a specific sign? Radiology 1992 Jan;182(1):221-4.