Application of Functional Alignment Principles and Stepwise Gap Balancing in Staged Bilateral Total Knee Arthroplasty for Severe Varus Knee Osteoarthritis With Lateral Femoral Bowing Using Conventional Instrumentation: A Case Report

Severe varus deformity with apparent lateral femoral bowing can complicate component alignment and softtissue balancing during total knee arthroplasty (TKA) performed with conventional instrumentation.Functional alignment principles emphasize restoration of balanced soft tissues and stable knee kinematics rather than rigid correction to neutral mechanical alignment.We report a case of bilateral Grade IV osteoarthritis with severe varus deformity managed using conventional jig-based TKA and rectangular gap balancing principles.A 70-year-old female presented with bilateral knee pain for more than 25 years associated with progressive deformity, difficulty in ambulation, and limitation of daily activities.Clinical examination revealed fixed varus deformity of approximately 20° on the right side and 15° on the left side, fixed flexion deformity of 20° bilaterally, medial soft tissue contracture, and relative lateral laxity.Flexion was preserved up to 110° and 115° in the right and left knees, respectively.Radiographs demonstrated bilateral Grade IV osteoarthritis with severe medial compartment degeneration and radiographic evidence of lateral femoral bowing.The patient, therefore, underwent staged bilateral TKA using conventional instrumentation, with the left knee replaced first, followed by the right knee during a subsequent admission after satisfactory recovery from the initial procedure.Femoral preparation was performed using a conventional intramedullary alignment guide.A 5° distal femoral valgus resection was performed on the left knee, while a 6° distal femoral valgus resection was used on the right knee.The resection angle was individualized according to the deformity characteristics and intraoperative assessment of coronal alignment and soft-tissue balance rather than applying a uniform valgus angle to both knees.Sequential balancing consisting of osteophyte excision, selective medial release, posteromedial release, and medial reduction osteotomy was performed to achieve balanced rectangular flexion and extension gaps.Postoperative radiographs demonstrated satisfactory component positioning and restoration of acceptable coronal alignment.Complex varus knee morphology and lateral femoral bowing may be successfully managed using functional alignment principles even when advanced technologies are unavailable.Careful deformity assessment and stepwise soft tissue balancing remain critical to achieving stable ligament tension and satisfactory knee kinematics.Functional alignment and rectangular gap balancing can be successfully achieved in severe bilateral varus knees with lateral femoral bowing using conventional instrumentation.Individualized balancing strategies may facilitate improved postoperative range of motion, Oxford Knee Scores (OKS), and clinically stable knees on examination without the need for robotic or navigation-assisted systems.