Anatomical Analysis of the Femoral Insertions of the Lateral Collateral Ligament and Popliteal Tendon in the Chilean Population: A Magnetic Resonance Imaging Study.

Background: Injuries to the posterolateral corner (PLC) of the knee can significantly impair stability and function. In particular, variations in the femoral insertions of the lateral collateral ligament (LCL) and popliteus tendon (PT) may affect surgical planning for PLC injuries. However, these anatomical features are underexplored in the Chilean population. This study seeks to characterize the femoral insertions of the LCL and PT in Chilean patients based on magnetic resonance imaging (MRI) findings. Methods: This cross-sectional, observational study was conducted at a single center, including 43 patients aged 18 and older who underwent knee MRI scans. Imaging was performed using a 1.5 Tesla MRI scanner with isotropic voxel dimensions of 0.65 x 0.65 x 0.65 millimeters. Two musculoskeletal radiologists independently measured the distance between the centroids of the LCL and PT insertion points on the femur. An intraclass correlation coefficient (ICC) was calculated to assess inter-observer reliability, and a paired t-test was used to compare the measurements. A p-value < 0.05 was considered statistically significant. Results: Among the 43 patients (51.2% male, 48.8% right knees), the average distance between the LCL and PT insertion centroids was 11.7 mm (SD 1.61). The measurements by the two radiologists were similar (observer 1: 11.5 mm; observer 2: 11.8 mm), with no significant differences (p = 0.326). The ICC for inter-observer agreement was 0.83 (95% CI: 0.69-0.91), indicating high reliability. Conclusions: In this Chilean cohort, the average distance between the LCL and PT femoral insertions was 11.7 mm, a value that differs from previously reported ranges. These findings may help refine surgical approaches to PLC injuries. Level of evidence: Level III, cross-sectional observational study.