Background: Obesity is one of the most serious health threats facing today's society that considering key risk factors for osteoarthritis development. This increase in total knee arthroplasty (TKA) is due to its superior postoperative outcome. Objective: This study aimed to reduce morbidity and improving outcomes of patients suffering from primary knee osteoarthritis by using TKA. Patients and methods: This study included 12 obese patients with advanced knee osteoarthritis at conducted in Orthopedic Department, Zagazig University Hospitals. All patients had undergone TKA prosthesis that used in this study was the NexGen Legacy posterior- stabilized (LPS)-Fixed Bearing Knee Systems with or without stem. All patients were followed up post operatively for clinical evaluations. Results: There are progressive improving of knee function, range of motion and whole patient lifestyle after TKA noticed obvious after 6 months from surgery as the score values show that mean post-operative KSKS score (45.42 ± 6.64) was higher than mean pre-operative KSKS score (73.17 ± 12.9), with change improvement 61.1% (p-value <0.001).  The Also, mean post-operative KSFS score (51.5 ± 3.8) was higher than mean pre-operative KSFS score (73.17 ± 12.90), with change improvement 41.3% (p-value <0.001). Conclusion: TKA in morbid obese patients, regardless their age and other comorbidities had many advantages as a very obvious pain improving. The functional improvement was very obvious with great impact on the whole lifestyle.