Fig. 1. Diagram of the rat tibia four-point bending apparatus with the rat in situ. (A) A mediolateral bending moment is produced in the portion of the tibial shaft between the two upper (padded) load points when a force is applied to the upper platen of the device. (B) By moving the lower load points inwards, so that they directly oppose the upper points, a force applied to the upper platen will squeeze the soft tissues intervening between the bone and the load points, as does the configuration depicted in A, but negligible bending of the shaft occurs. This sham configuration allows assessment of the effect of soft tissue irritation (and consequent inflammatory response) on bone formation, as distinct from a coordinated mechanically adaptive response (Robling et al., 2000).