Risk Factors for Foot and Ankle Pain After Total Knee Arthroplasty and the Role of Subtalar Joint Motion Capacity

Introduction: Total knee arthroplasty (TKA) restores the mechanical axis of the lower extremity, which is impaired due to gonarthrosis. Foot and ankle pain observed after TKA is not uncommon, and the exact cause has not been determined. This study aims to assess the role of the movement capacity of the subtalar joint and the clinical and radiological risk factors for foot and ankle pain after TKA. Methods: This study included 184 patients who underwent TKA due to primary varus gonarthrosis. Patients were evaluated clinically and radiologically before and after surgery. Lower extremity mechanical axis, talar-tilt angle, foot ground-talar dome angle, heel alignment ratio, heel alignment angle, heel alignment distance, and postoperative changes were the radiological angles measured. The Oxford Knee Score, American Orthopaedic Foot and Ankle Society Ankle-Hindfoot Score, visual analog scale score, and ankle and subtalar joint range of motion examinations were used clinically. Patients were grouped as those whose American Orthopaedic Foot and Ankle Society scores did not worsen after surgery (group 1) and those whose scores worsened (group 2). Results: The group 1 included 142 patients (77.2%) and group 2 included 42 patients (22.8%). The mean preoperative knee varus degree of group 1 was 11.49 ± 3.45, and that of group 2 was 14.26 ± 4.21 ( P < 0.001). The mean body mass index was 26.67 ± 2.31 for group 1 and 29.47 ± 3.14 for group 2 ( P < 0.001). Although no important difference was found between the groups in preoperative ankle motion capacity ( P = 0.086), subtalar joint motion was found to be markedly limited in group 2 ( P < 0.001). Conclusion: High preoperative knee varus degree and body mass index values, especially diminished preoperative subtalar joint motion capacity together with these values, are risk factors for postoperative foot and ankle pain after TKA. Level of Evidence: Level III, Retrospective comparative study.