[TA] synovial tendon sheaths of flexor tendons enabling movement of tendons posterior to the lateral malleolus and across tarsal bones, passing deep to the fibular retinacula; includes (1) the common tendinous sheath of fibulares (peronei) muscles [TA] (vagina communis tendineum musculorum fibularum (peroneum) [TA]); and (2) the plantar tendinous sheath of fibularis (peroneus) (muscle) [TA]) (vagina plantaris tendinis musculi fibularis (peronei) longi [TA]). SYN: vaginae tendinum tarsales fibulares [TA].