Background: To measure the degree of varus deformity in primary osteoarthritis knee and compare the various degree of varus deformity and knee function. Method: The Mechanical axis of the femur (MAF) and the Mechanical axis of the Tibia (MAT) to measure angle of varus deformity The patient was clinically examined and assessed for the function of the knee using the American Knee Society function score (AKSS) [Excellent, Good and Poor]. Result: Among 41 patients with 0 to 10 degrees of varus deformity, 53.65% had excellent (80-100) and 46.34% had good (70-79) knee society function scores. Among 32 patients with 11 to 15 degrees of varus deformity, 50% had excellent (80-100), 31.25% had a good (70-79) knee society function score, and 18.75% had a fair (60-69) knee society function score. Among 16 patients with 16 to 20 degrees of varus deformity, 75% had a poor (60) knee society function score, 12.5% had a fair (60-69) knee society function score, and 6.25% had a good (70-79) and 6.25% had excellent (80-100) knee society function score. Among 11 patients with 20 degrees of varus deformity, 100% had poor (60) knee society function scores. Hence, there was a statistically significant difference in the proportion of knee society function scores according to the degree of varus deformity (p0.05). The correlation between the degree of varus deformity and the AKSS was found to be statistically significantly high and negative (Correlation coefficient: -0.880; p<0.001). Conclusion: With the increase in the degree of varus deformity, there was a decrease in knee function score in primary osteoarthritis knee patients.