A good outcome in total knee arthroplasty depends on many factors: joint alignment, range of motion, patellar tracking and ligament stability. A correct soft tissue balance keeps the joint aligned in flexion and extension, and therefore constitutes the most important factor for durability of the implant. Indeed, incorrect soft tissue balancing is the primary cause of early implant failure necessitating revision surgery. Soft tissue releases, serving to correct imbalances, are performed until the flexion and extension gaps appear symmetrical and balanced. A knee is considered perfectly balanced when the flexion and extension gaps are perfectly rectangular and all the measurements are absolutely equal.Key Words: balance, ligament, total knee arthroplasty, valgus, varus. IntroductionA good outcome in total knee arthroplasty (TKA) depends on many factors: joint alignment, range of motion, patellar tracking and ligament stability. A correct soft tissue balance keeps the joint aligned in flexion and extension, and therefore constitutes the most important factor for durability of the implant; indeed, incorrect soft tissue balancing is the primary cause of early implant failure necessitating revision surgery.In the osteoarthritic joint, instability can be symmetrical causing cartilaginous or bony erosion without ligament changes, or asymmetrical. Asymmetrical instability, which is typical of severe osteoarthritis (OA), is characterized by the inevitable occurrence of structural soft tissue changes, serving to compensate for the deformity caused by asymmetrical bone loss. Such joint instability cannot be corrected by bone resections and implant alignment alone (Fig. 1). In the surgical correction of an asymmetrical joint deformity it can be necessary to perform additional procedures to ensure retention of the stretched ligamentous structures, or, if these are not sufficient, to opt for a constrained type of implant. In this regard, it is necessary to bear in mind the requirements of younger patients, in whom every effort should be made to avoid the use of constrained implants. Each single patient should be evaluated carefully and treated individually. Accurate and thorough pre-operative planning with full-length standing radiographs of the lower limb in anteroposterior and lateral views, and axial view are indispensable for choosing the prosthesis design and tibial bone resection level (1, 2). Testing for soft tissue balancing during TKA was introduced by Insall, who used spacer blocks and laminar spreaders intraoperatively to assess the extension and flexion gaps in varus and valgus stress (2). It is recommended that all osteotomies of the tibia and femur be performed first, followed by excision of all osteophytes. Posterior femoral condylar osteophytes should be excised because they can prevent full extension and influence posterior soft tissue tension (Fig. 2). Before performing soft tissue release for balancing, it is important to remember the following points: Soft tissue balancing in total knee arthroplasty...

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