An insert for balancing a joint during repair of the joint, the insert comprising: a first plate configured to interface with a bone structure of a joint; a second plate including a plate portion (120, 109) spaced apart from the first plate and configured to interface with an opposing bone structure of the joint, a transition portion extending from the plate portion protruding beyond the perimeter of the first plate, and a mounting portion extending beyond the first plate in a transverse direction relative to the transition portion in the direction of the first plate and an actuator located between the first plate and the plate portion and configured to apply a force to the plate portion, characterised in that the mounting portion further comprises a body extending downward from the transition portion, a first leg extending downward from the body, a second leg extending downward from the body adjacent to the second leg forming an outer recess there between, a first mounting guide protruding from the first leg, and a second mounting guide protruding from the second leg. a first plate configured to interface with a bone structure of a joint; a second plate including a plate portion (120, 109) spaced apart from the first plate and configured to interface with an opposing bone structure of the joint, a transition portion extending from the plate portion protruding beyond the perimeter of the first plate, and a mounting portion extending beyond the first plate in a transverse direction relative to the transition portion in the direction of the first plate and an actuator located between the first plate and the plate portion and configured to apply a force to the plate portion, characterised in that the mounting portion further comprises a body extending downward from the transition portion, a first leg extending downward from the body, a second leg extending downward from the body adjacent to the second leg forming an outer recess there between, a first mounting guide protruding from the first leg, and a second mounting guide protruding from the second leg. a plate portion (120, 109) spaced apart from the first plate and configured to interface with an opposing bone structure of the joint, a transition portion extending from the plate portion protruding beyond the perimeter of the first plate, and a mounting portion extending beyond the first plate in a transverse direction relative to the transition portion in the direction of the first plate and an actuator located between the first plate and the plate portion and configured to apply a force to the plate portion, characterised in that the mounting portion further comprises a body extending downward from the transition portion, a first leg extending downward from the body, a second leg extending downward from the body adjacent to the second leg forming an outer recess there between, a first mounting guide protruding from the first leg, and a second mounting guide protruding from the second leg. a body extending downward from the transition portion, a first leg extending downward from the body, a second leg extending downward from the body adjacent to the second leg forming an outer recess there between, a first mounting guide protruding from the first leg, and a second mounting guide protruding from the second leg.