Joint line level in revision total knee replacement: assessment and functional results with an average of seven years follow-up

Introduction It has been shown that the distance between the joint line (JL) and the fibular head is constant in both knees in a given individual. We analysed the influence of the JL level difference between the revised knee and the native knee from the functional outcomes after TKR revision. Methods This multicentre study assessed retrospectively a consecutive series of 177 revised total knee replacements. Patients with contralateral knees that had undergone previous major surgery or trauma were excluded. The JL level difference between both knees was measured on Knee's AP standing X-rays and compared to the KSS Knee and Function scores at the final follow-up. Results Eighty-five cases were analysed at a mean of seven years follow-up. There was a significant increase in KSS Knee and Function scores after surgery. The average elevation of the JL was 2.2 mm (s.d. 2.66 mm) compared with the healthy contralateral knee. When the JL was elevated more than 4 mm this correlated with a decreased KSS Function score and decreased post-operative knee flexion. Conclusions Poorer functional results are significantly associated with an elevation in the JL compared to the contralateral healthy knee. In those patients with a suitable contralateral knee the JL level to restore can be assessed by the distance between the femoral condyle and the apex of the fibular head of the contralateral knee.