Lateral femoral notch sign - ACL tear

Case contributed by Khalid Alhusseiny

Presentation

Painful right knee following twisting injury 10 days earlier.

Patient Data

Age: 25 years
Gender: Male

Right knee

x_ray

There is a bony depression seen along the lateral femoral condyle (lateral femoral notch sign) suggestive of an anterior cruciate ligament (ACL) tear. The suprapatellar fat pad is obliterated denoting joint effusion.

Right knee

mri

MRI was performed after the initial x-ray. It confirms the ACL tear with interruption of its fibers mainly at the femoral attachment. Associated bony bruises/edema are seen involving the lateral femoral condyle and proximal tibia. The medial collateral ligament is sprained. Moderate amount of knee joint effusion is seen.

Case Discussion

Lateral femoral notch sign refers to the appearance of osteochondral injury that occurs as a result of the impaction injury of the femoral condyle and tibial plateau during rotational movement. The sign can correlate well with an ACL tear in the context of a clinical history of twisting knee injury.

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