Unstable Total Knee Arthroplasty

Cho, Woo Shin

Abstract

Instability after total knee arthroplasty (TKA) is directly related with the success of an operation. It has been reported that about 10~22% of revisions are caused by instability. The patient's satisfaction is diminished from the early stage of the postoperative period due to pain, recurrent swelling and difficulty when walking. Complications such as infection, wear and the loosening rate are also increased. There are many factors causing unstable TKA. Among the patients factors, neuromuscular pathology, other joint deformity and clinical obesity may play a role. These factors can be avoided by careful preoperative evaluation of patients. Yet the most common causes of instability are from the surgical technique, including the size of the implant, the alignment, gap balancing, soft tissue release and the patella tracking. Surgeons can achieve stable joint by performing a proper surgical procedure. Postoperatively trauma and overuse may provoke instability and patients can feel an unstable knee as a result of wear and loosening. Knee instability can be classified into the instability of flexion and extension, genu recurvatum and global instability. The first step to treat instability is to detect the causes of instability. The second step, of course, is to correct the causes. Either conservative treatment or revision surgery can be chosen according to the degree and causes of instability. Because the result of revision treatment is not as successful as primary TKA, careful evaluation of the patient as well as a meticulous surgical procedure should done for revision TKA.