Query: Persistent complaints following implantation of a knee prosthesis are often a problem which is hard to overcome. On the one hand, general diagnostics do not reveal the cause of the complaints, on the other, pain symptoms in connection with deficient patella control cannot always be attributed to insufficient equilibrium of the soft tissues. In this prospective study, the rotation of the components was examined in connection with the pain described by 49 patients.

Method: The rotation of the prosthesis components was examined by means of axial CT scans in 49 patients with the complaint symptoms described above and without signs of loosening or malpositioning at the frontal or sagittal level. The results were set in relation to clinical symptoms, the Knee Society Score and a VAS.

Results: A direct relationship was found between the extent of the added inner rotation malpositioning of the components and a deteriorated Knee Score. No difference in the pain score in dependence on the extent of improper implantation could be observed. Incorrect tibial rotation was responsible in particular for patellar lateralization, subluxation or tipping.

Conclusion: The correlation between inner rotation malpositioning and deficient patellar control or signs of instability underlines the importance of intraoperative rotation adjustment in the prevention of knee pain. In unclear knee pain following knee endoprosthesis implantation, performance of a CT to determine the component rotation is indicated. If there is a rotation malpositioning, correction in a revision procedure should be considered.