Background: Manual thigh girth measurement is a simple tool to roughly estimate capacity change of the thigh. Yet, there is no good evidence supporting the most relevant anatomical landmarks to detect girth difference from the normal limb.
Material and Method: The present study consecutively enrolled 30 patients sustaining unilateral anterior cruciate ligament deficiency and measured both thigh girths in series at 2-cm intervals from anteromedial joint line until 30 cm cephalad. The measurements were also performed in intervals at 1/16 ratio of the thigh length marked between the tibial tuberosity (TT) and the anterior superior iliac spine (ASIS). The results from both normal and the injured side were compared by analyzing means and standard deviations for the statistical difference.
Results: Levels of significant mean girth difference between the two thighs were located at 18 cm and 20 cm above the anteromedial joint line or at 6/16 (3/8 or approximately 1/3) the thigh length measured from the TT towards the ASIS.
Conclusion: In patients with knee problems using deficient ACL as the prototype, the most relevant level to detect thigh girth difference from the normal side is located at 18 cm and 20 cm above the anteromedial knee joint line or at 6/16 (3/8 orapproximately 1/3) the thigh length measured from the TT towards the ASIS.

Keywords: Thigh, Circumference, Girth, Measurement, Anterior cruciate ligament