The cruciate ligaments are generally regarded as regulators of the joint kinematics, but also increasingly as a "Sensory organ" regulating the periarticular musculature, which influences the position of the contact surfaces and the direction and magnitude of the resultant forces. Indirectly, therefore, they influence the long-term stress distribution, which is itself reflected in the distribution of the subchondral mineralisation. An experimental investigation was therefore undertaken to see whether, in terms of this distribution, the distribution of the stress alters postoperatively, since this could be regarded as an early cause of degenerative change. We examined the distribution of the subchondral mineralisation of six tibiae from six adult Merino sheep 1 year after anterior cruciate ligament reconstruction with patellar tendon. The contralateral tibia we used as controls. Maximum subchondral mineralisation of both the medial and the lateral joint surfaces in all the control joints was found to be central. In the treated knees, however, the medial joint surface maxima were found to have been displaced towards the dorsomedial edge of the surface in every case. If the density pattern on the control side is accepted as the expression of a normal stress distribution, the distribution patterns on the treated side must indicate a pathologic distribution of stress. Reconstruction of the anterior cruciate ligament is therefore--at least in the animal model--not able to prevent the development of a pathologic stress distribution.(ABSTRACT TRUNCATED AT 250 WORDS)