Total Knee Arthroplasty in Patients With Ankle Osteoarthritis Affects Contralateral Ankle Alignment and Postoperative Outcome of Total Knee Arthroplasty

Background: This study investigated the impact of total knee arthroplasty (TKA) on the alignment of the ankle joint, focusing on changes in coronal alignment of both ankles. Methods: This retrospective study, conducted at our hospital, included 64 patients older than 70 years who underwent TKA for varus knee osteoarthritis (OA). Using full-length standing radiographs of both lower extremities taken preoperatively and 6 months postoperatively, we assessed ankle OA grading based on the Takakura-Tanaka classification and measured mechanical hip-knee-ankle (mHKA) and the tibiotalar angle (TTA) on both the surgical and contralateral side. Additionally, we examined the impact of ankle OA on postoperative clinical scores, the Knee injury and Osteoarthritis Outcome Score, following TKA. Results: Based on the classification, ankle OA stage 2 or higher was present in 13 cases on the surgical side and 13 cases on the contralateral side. On the surgical side, mHKA changed from 12.2 to 1.8 degrees varus ( P < .001) and TTA from 1.7 to 1.0 degrees varus ( P = .002). On the contralateral side, mHKA changed from 4.0 to 5.4 degrees varus ( P = .04), and TTA from 2.7 to 3.0 degrees varus ( P < .001). In ankle OA stage 2 or higher patients, contralateral TTA changed from 5.2 to 6.5 degrees varus ( P < .001) and unchanged in stage 1 patients. Ankle OA stage 2 or higher patients had worse ADL outcomes than stage 1 patients (score: 67.2 and 78.3, respectively, P = .03). Conclusion: This study suggests an apparent interrelationship between knee and ankle OA and the potential negative influence of TKA on ankle OA.