During the development of degenerative joint disease (osteoarthritis, chondropathy), a diagnostic or even pathogenetic role is attributed to the phenomenon of intraosseous pressure (IOP). Owing to technical problems and a lack of systematic experimental or clinical studies on the control mechanisms of the IOP, the actual importance of this factor is still not known with certainty. Now, a measuring method that enables correct recording of the IOP and standardized on-line processing of the measured signal minimize artefact-related problems. The technique is evaluated for reliability in an in vitro model of the human patella and in a limited clinical study of the IOP in patients undergoing knee surgery for various reasons. Factors such as intra-articular effusion, joint position or changes in intra-articular soft tissue are examined for their influence of the primary signal.