Background: soft tissues balancing and flexion knees deformity were difficulties’ in patients with advanced knee arthritis managed by Total Knee Arthroplasty (TKA). Objectives: the purpose of our study was the evaluation of clinical and radiological results of patients with advanced primary Osteoarthritis knee with fixed flexion deformity. Patient & Method: prospective study of twenty five knees (twenty one patients unilateral and two patients bilateral) with primary Advanced OA with moderate to severe fixed flexion deformity with varus knee deformity in ten knees (varus range 15- 25o). All patients were managed by primary TKA with appropriate soft tissues balancing from June, 2010 to July, 2018 in our university hospital. There were 9 male and 12 female with bilateral knee deformity in two female patients. They were classified into two groups, group I: patients with moderate flexion deformity (MF) with flexion deformity less than 30°, in 14 knees (56%) and group II: patients with severe flexion deformity (SF) with flexion more than 30° in 11 knees ( 44%). Metal augment in 7 knees long stem tibia in 4 cases 100 mm all was sacrificed PCL with posterior stabilized prosthesis. The patient’s clinical and radiological information were evaluated preoperative, Intraoperative and postoperative at a standard period and yearly follow up for two years. Results: We had no intraoperative complications in this study. Soft tissue release surgery and additional bone cuts were performed in group II. The mean age was 59±5.97 (range 48-71), mean flexion contracture deformity was 34±11.63 (range 20-60), mean preoperative ROM was 65±9.34 (range 45-80) and mean postoperative ROM was 99±932 (range 65-110). There was no difference between group I and group II postoperative ROM (112±10.23 and 115±9.2). In group I mean Knee Society Score (KSS) improved from 34 (0 to 71) to 88 (38 to 100) (p < 0.001) and the KSS Functional Score from 43 (0 to 70) to 86 (0 to 100). No knees required manipulations under anaethesia (MUA) and none of the knees had flexion instability. Group II mean Knee Society Score (KSS) improved from 28(0 to 56) to 85 (40 to 100) and the KSS Functional Score from 43 (0 to 70) to 84 (0 to 100). Two knees (8%) required manipulations under anaethesia (MUA) and none of the knees had flexion instability. We had no infection complication and no cases with patellar dislocation or subluxation seen in this study. Conclusion: Preoperative planning of the knees with severe flexion contracture managed by primary TKA with good soft tissues balancing can be performed successfully.