A lead assembly for an implantable medical device includes a lead body having a proximal end, a distal end, and a longitudinal axis that extends between the proximal end and distal end. The lead assembly also includes a strain relief tube that surrounds a portion of the lead body. The strain relief tube includes a flexible material configured to include contours such that the portion of the lead body surrounded by the strain relief tube maintains a formed shape that varies from the longitudinal axis of the lead body. The contours vary in response to forces on the lead body to prevent strain at the distal end of the lead body.