A portable joint testing device that generates reproducible measurements of rotation about all three axes with load-bearing activities includes a first position sensor mounted on a first bone proximate the joint for transmitting first position data； a second position sensor mounted on the second bone proximate the first joint for transmitting second position data； and at least one force sensor mounted on the second bone for quantifying forces applied to the second bone and for transmitting force data. A controller collects the force data and the first and second position data, and transmits or generates a laxity envelope for varus/valgus and/or internal/external rotation of the first bone relative to the second bone or vice versa.
