Prospective and experimental clinical study on the effects of knee joint deformities and the implantation of a total knee arthroplasty on the ankle joint

Introduction: Clinical experience has shown that patients may complain of ankle pain after total knee arthroplasty. However, this observation has so far only been reported in retrospective studies and case reports. The aim of this study was to validate the evidence of this phenomenon in a prospective study. In addition, it was planned to study the influence of coronal and sagittal knee joint deformities as well as the implantation of a TKA on the ankle joint radiologically and functionally in order to ultimately identify risk factors for developing ankle pain after TKA. Methods: Patients with end-stage osteoarthritis of the knee joint who were planned to undergo TKA were included in this prospective study. The examinations were carried out one week preoperatively and three months postoperatively. The knee and ankle joints were examined clinically and radiologically (mTFA, TT, HAVA, ADTA, Meary's angle). Subjective complaints of the ankle and knee joint were assessed using patient-reported outcome measures. Ankle joint stability was recorded using an arthrometer. Gait analysis was performed using insoles with pressure-sensitive sensors. Preoperatively, 82 patients (varus n=52, valgus n=30), postoperatively 69 patients (varus n=45, valgus n=24) were examined. Results: The mTFA correlated significantly with the HAVA (cor=-0.72, p=<0.001) and the TT (cor=0.23, p=<0.006) preoperatively. In contrast, higher values of the mTFA did not correlate with inversion (Varus: cor=-0.24 p=0.095 Valgus: cor=0.11, p=0.5) or eversion capacity (Varus: cor=0.27, p=0.06, Valgus: cor=0.3, p=0.11). The ADTA significantly correlated with posterior translation (cor=0.24 p=0.049). The varus group showed a lateral gaitline preoperatively, although the hindfoot was positioned in valgus. Patients in the valgus group showed medialised gaitlines despite a hindfoot varus. Postoperatively, 16 patients (23.2%) reported increased ankle pain. Risk factors for increased ankle pain were a preoperatively increased TT in the varus group and a preoperatively pathologically lateralised gaitline in the valgus group. Postoperative ankle pain did not correlate with the mTFA, restricted ankle ROM or ankle instability. Conclusion: The observation that patients may complain of increased ankle symptoms after TKA was confirmed in this study. Preoperatively, an increased TT (varus group) and a lateralised gaitline (valgus group) were identified as risk factors. Therefore, patients with varus knee osteoarthritis and postoperative ankle symptoms, who have an increased TT, could benefit from insoles with a lateral shoe edge or in select cases from supramalleolar realignment osteotomies. Patients with valgus knee osteoarthritis and postoperative ankle pain who have a lateralised gaitline could, for example, be treated with physiotherapy and gait training.