This article examines the extent of anterior knee soft-tissue stretching that occurs in patients undergoing primary total knee arthroplasty for 331 consecutive patients. At the time of surgery, an anterior knee incision was drawn on the knee. Measurements were taken of the length of the incision with the knee in maximum extension and 90 degrees degrees of flexion. Incision length was 5.7 cm longer in flexion than extension. The surgical incision site stretched an average of 23.6% in flexion compared to the resting extension length.