A cardiac lead includes a lead body that defines a passage, a conductive element that extends through the passage, and a fixation assembly. The fixation assembly includes a threaded member threadably engaged with the conductive element such that rotation of the threaded member causes the threaded member to translate longitudinally relative to the conductive element. A fixation element has a first end coupled to the threaded member and a second end coupled to a fixed location. A resilient membrane extends over the fixation element such that rotation of the threaded member affects the resilient membrane radially with respect to the conductive element.