n 1  :  either of two fibrous bands of fascia crossing the front of the ankle  a  :  a lower band that is attached laterally to the superior aspect of the calcaneus and passes medially to divide in the shape of a Y and that passes over or both over and under the tendons of the extensor muscles at the ankle - called also inferior extensor retinaculum   b  :  an upper band passing over and binding down the tendons of the tibialis anterior, extensor hallucis longus, extensor digitorum longus, and peroneus tertius just above the ankle joint - called also superior extensor retinaculum , transverse crural ligament   2  :  a fibrous band of fascia crossing the back of the wrist and binding down the tendons of the extensor muscles .
 
 
 
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