Constraint is limitation of motion in a joint, e.g., due to an axis mechanism or to conformity between two articular surfaces.In addition to flexion and extension,the normal knee has some anterior-posterior translation and rotates around a vertical axis. If these motions are impeded by excessive constraint in a prosthetic design, no physiological motion will be possible. Unfavorable long-term results and complications have been reported in this setting. Possible sequels of excessive constraint are fatigue of the bone-prosthesis interface, limitation of motion, patellar displacement, or periprosthetic fracture. ConstraintConstraint is limitation of motion between two bodies linked by a joint.