Background: The kneeling stress radiograph is valuable for quantifying posterior cruciate ligament (PCL) injuries. However, this method presents drawbacks, including patient discomfort during filming, radiation exposure, variability attributable to patient cooperation, and technician skill requirements. The modified Lachmeter technique offers an alternative approach. Its notable advantages are reproducibility, less patient pain or discomfort, and reduction of radiographic exposure.
Purpose: To compare and find the correlation of the side-to-side difference (SSD) value between the modified Lachmeter technique and the kneeling stress radiograph.
Study design: Cohort study (diagnosis); Level of evidence, 2.
Methods: A total of 33 patients with isolated PCL injury were measured for the SSD value using a modified Lachmeter technique and a kneeling stress radiograph. Demographic data and SSDs were collected from each method and analyzed.
Results: The sample entailed 26 men and 7 women, with a mean of 37.58 years (range, 15-65 years). There were 14 patients with right knee injuries and 19 patients with left knee injuries. The mean difference in absolute values between the 2 methods was 2.32 ± 2.29 mm. Interobserver and intraobserver intraclass correlation coefficients of the modified Lachmeter showed almost perfect agreement (0.909 and 0.977, respectively).
Conclusion: The SSD showed an excellent correlation between the modified Lachmeter technique and kneeling stress radiographs. Consequently, the modified Lachmeter technique holds promise as an alternative to stress radiography for patients with isolated PCL injuries.
Keywords: PCL injury; modified Lachmeter technique; posterior cruciate ligament; side-to-side difference; stress radiography.
© The Author(s) 2025.