Flexion and extension instability

Total knee replacement is one of the most successful orthopedic procedures, yet failures still occur. Instability in flexion or extension represents one of the frequent causes of unsuccessful outcomes. Although trauma may cause acute ligamentous injury, the majority of cases of instability are likely due to intraoperative decisions. Failure to restore medial-lateral soft tissue balance with symmetric flexion and extension spaces may produce postoperative instability. In this article the etiologies and management of instability are reviewed. In addition, surgical techniques for creating symmetric, balanced flexion and extension gaps are presented.