Method: Twenty-seven patients were included in this study conducted from 1st January to 31st December 2013. All patients were skeletally mature and scheduled to undergo primary anterior cruciate ligament reconstruction using 4S-STG autograft. Ultrasonographic examination of semitendinosus and gracilis tendons to measure the cross sectional area was conducted and anthropometric data (weight, height, leg length and thigh circumference) was measured one day prior to surgery. True autograft diameters were measured intraoperatively using closed-hole sizing block in 0.5 mm incremental size.

Results: There is a statistically significant correlation between the measured combined cross sectional area (semitendinosus and gracilis tendons) and 4S-STG autograft diameter (p = 0.023). An adequate autograft size (at least 7 mm) can be obtained when the combined cross sectional area is at least 15 mm2. There was no correlation with the anthropometric data except for thigh circumference (p = 0.037). Autograft size of at least 7 mm can be obtained when the thigh circumference is at least 41 mm.