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The cruciate ligaments were resected with their bony insertions during total knee arthroplasty carried out in 12 patients with severe rheumatoid or osteoarthritis. The ligaments were examined histologically and biomechanically, using ten specimens from healthy adults as a control. A significant difference was found in the tensile stiffness and viscoelastic properties of the ligaments between the arthritic and the control group. The ligaments in the rheumatoid knees had a distinctly inferior tensile strength compared with the osteoarthritic knees. Total knee replacement, which also replaces ligament function, should therefore be considered in severely damaged rheumatoid knees.

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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.

Compared to injuries of the other knee ligaments, a rupture of the posterior cruciate ligament (PCL) is relatively rare. Treatment may be conservative or operative. A rupture that has been operated on temporarily can be stabilised using a Grammont patello-tibial transfixation (olecranisation). Flexion and extension between 30 degrees and 60 degrees are allowed. The advantage of this method is that it avoids complete immobilisation of the joint and also the reduction of pull on the PCL. However, patients treated with this method show long-term osteoarthritis of the retropatellar joint area. Our study aimed to show the distribution of forces at the dorsal patellar surface in the following: (1) knee with intact ligaments; (2) knee with PCL rupture; (3) knee with PCL rupture plus olecranisation. Fourteen fresh knee specimens were investigated in a Plitz/Wirth knee kinemator. The femur was fixed while the tibia was flexed between 5 degrees and 120 degrees. Pull was placed on the patella and on the dorsal side of the tibia with weights over the tendons of the quadriceps and the roots of the ischio-crural muscles. With the aid of a special measurement device in the patella, the medially laterally, proximally and distally acting forces in a movement cycle could be measured as well as the total retropatellar force in the above experimental setups.(ABSTRACT TRUNCATED AT 250 WORDS)