Background: muscular strength training improves range of motion, muscle strength, and functional capacity in patients with knee osteoarthritis (OA) OBJECTIVE: The aim of this study was to compare the effects of low-repetition high resistance and high repetition low resistance strengthening training of calf muscle in patients with mild and moderate knee osteoarthritis. METHODS: Forty-eight patients of both genders with mild to moderate bilateral knee osteoarthritis, their age ranged from 50-60 years. The patients were randomly assigned into three groups, group (A): 16 patients received conventional physical therapy treatment only. Group (B) consisted of 16 patients received conventional physical therapy and low repetition high resistance training of calf muscle. Group (C) consisted of 16 patients received conventional physical therapy and high repetition low resistance training of calf muscle. RESULTS: The study found a significant decrease in VAS and WOMAC in group B and group C compared to group A, but no significant difference in VAS between the two groups. However, group B showed significant increases in the strength of their right and left calf muscles compared to group A and C. CONCLUSION: Resistance training exercises for calf muscles are recommended as in adjunct to the treatment’s protocols for patients with knee osteoarthritis. Both high and low resistance training is effective in improving pain and function in patients with knee osteoarthritis. Also, high resistance training exercises are more effective than low resistance exercises.