The proximal interphalangeal joint (PIPJ) has always been considered as a low-motion joint with an almost constant angle during loading of the limb. Until very recently, its motion was not taken into account in kinematic studies in vivo. Recent in vivo studies yielded surprisingly high ranges of motion in this joint. The aim of this study was to measure, in terms of the 3 possible rotations (flexion/extension, collateromotion and axial rotation), the movements of the PIPJ in vitro during limb loading in a neutral position (500-6000 N) and after the addition of heel and toe wedges (6 degrees and 12 degrees). The joint coordinate system, as it was recently described for use in the horse, was used to compute the 3 components of rotation. With the hoof in neutral position, low-amplitude flexion movements (7.9 degrees) were observed. They were not associated with collateromotion or axial rotation. The flexion of the joint increased exponentially with load suggesting that, during the midstance phase, heavy loads are necessary to evoke substantial flexion. Raising the heels induced an early flexion of the joint with an increase of its total amplitude. Raising the toe produced an extension at 500 N, beyond which the amount of flexion was reduced. These results show that PIPJ flexion/extension during in vitro loading remains substantially smaller than suggested by in vivo studies based on skin markers. Raising the toe or heel directly affects the behaviour of this joint, but does not induce motion outside the sagittal plane. Hoof wedges are commonly used in clinical practice for purposes other than affecting PIPJ motion. In these cases, their biomechanical effects on this joint should be taken into account.