Unexplained pain following total knee arthroplasty: Is rotational malalignment the problem?

Background: Malrotation of tibial and femoral components is a potential source of pain following total knee arthroplasty (TKA). This study aimed to 1) compare component rotation in TKA patients with unexplained pain versus a control group with well-functioning TKAs and 2) investigate the relationship between TKA component rotation and pain. Methods: Seventy one patients with unexplained pain after primary TKA were compared to a control cohort of 41 well functioning TKA patients. Both groups underwent post-operative computed tomography (CT) scans to assess component rotation. Findings were compared between the painful and control TKA groups. Results: We found no difference in femoral component rotation between the painful and control groups (mean 0.6° vs 1.0° external rotation (ER), p = 0.4), and no difference in tibial component rotation (mean 11.2° vs 9.5° internal rotation (IR), p = 0.3). Also, there was no difference in combined mal-rotation (tibial + femoral rotation) between the groups (mean 10.5° vs 8.5°IR, p = 0.25). Fifty-nine percent of patients in the painful group had tibial component rotation > 9°IR vs 49% in the control group. Conclusion: In the largest study yet on component rotation after TKA, we found no difference in the incidence of tibial, femoral, or combined component mal-rotation in painful versus well-functioning TKAs. Tibial component IR relative to the junction of the medial to middle thirds of the tibial tubercle appears to be common in patients with well-functioning TKAs. The significance of slight tibial IR should be interpreted with caution when evaluating the painful TKA. Level III retrospective case–control study.