Complete rupture of the anterior tibial tendon.

The axial fast spin-echo T2-weighted image was obtained just below the tibial plafond. At this level, the anterior tibial tendon (ATT) is normally seen in cross section as a black oval structure anterior to the joint. On this image, the tendon sheath of the ATT is distended with T2-hyperintense material (arrow), but the tendon is not visible. The extensor hallucis longus (EHL), extensor digitorum longus (EDL), and peroneus tertius tendons (PT) are visible anteriorly. A portion of the oblique superomedial limb of the inferior extensor retinaculum (IER) is visible on either side of the empty ATT sheath.

The coronal image includes portions of the anterior tibial tendon (ATT) and extensor hallucis longus (EHL) tendons over the anterior tibia. The ATT appears thickened and terminates abruptly (arrow), rather than continuing to its usual insertion.

The sagittal fat suppressed fast spin-echo T2-weighted image visualizes the retracted torn ATT just anterior to the medial distal tibia (arrow), corresponding to the palpable mass on physical examination. The torn end of the tendon displays a thickened bulbous morphology, with increased intrasubstance signal.

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