Apparatus and methods for positioning a body part of a patient. An apparatus can comprise a portable support structure configured to be placed on a patient support surface under a body part of a patient and retention elements attached to the support structure. At least a portion of the support structure is configured to move from lowered position to a raised position above the lowered position. The retention elements are configured to receive the body part. Each retention element has a holding portion and an open region, and each retention element faces at least partially sideways in a retention position.