A ligament-tensioning device and method for activation of the ligament and/or capsule system in the implantation of a joint implant. The device includes a distal bearing plate for bearing against a distal skeletal part, and also includes first and second proximal bearing plates, each of which partially overlaps the distal bearing plate in a first in-use position, for bearing against a proximal skeletal part. The device further includes means for relative displacement of the proximal bearing plates to increase their spacing from the distal bearing plate. The displacement means includes a scissor-type guide means that supports the respective proximal bearing plate in the ventral-dorsal as well as the medial-lateral parallel position with respect to the distal bearing plate.