Introduction. The mobility of the lateral meniscus body is restricted by a menisco-tibio-popliteus-fibular complex (MTPFC), composed by the lateral menisco-tibial ligament (LMTL), the popliteo-fibular ligament (PFL) and the popliteo-meniscal ligaments (PML). The aim of this study was to identify, measure and determine the main structures of this anatomic complex by Magnetic Resonance Image (MRI).

Methods. 105 knees without prior injury neither surgical history were analyzed by MRI in a Reference Center for Musculoskeletal Radiology. 60% were right knees and 40% were left with an average age of 50.13 years ± 14.86 (37.70 - 62.55). 58 knees (55.2%) corresponded to male patients and 47 knees (44.76%) to female patients. All the measurements were performed by two musculoskeletal radiologists. The peripherical structures of the lateral meniscus body were identify to determine the location, size and thickness of the whole MTPFC and of each one of its three main structures described (LMTL, PFL and PML). The distance to other “key areas” in the lateral compartment was also studied and compared by gender.

Results. The LMTL was found in 97.1% of the MRIs, 93% for the PFL and 90.4% for the PML. There were no significant differences between the prevalence of the MTPFC between genders. The anteroposterior distance (mm) of the LMTL in an axial view was 20.70 ± 3.95 (20.70 ± 3.95), the anterior thickness of the LMTL middle 1.14mm (SD ± 0.31; 95% CI: 0.87-1.40), and the posterior thickness of the LMTL 1.26mm (SD ± 0.17; 95% CI: 1.12-1.40) and the height (mm) in a coronal view was 10.80 ± 1.99 (9.13-12.47). The lenght (mm) of the PFL in a coronal view was 8.72 ± 2.51 (6.62-10.82), the thickness (mm) was 1.42 ± 0.47 (1.02-1.82) and the width (mm) in an axial view was 7.86 ± 2.23 (5.98-9.73). The length (mm) of the inferior PML was 12.85 ± 2.24 (10.97-14.73) and 16.23 ± 3.42 (12.38-19.33) for the superior PML. The width of the PML was 3.08 ± 0.62 (2.55-3.60) and the thickness (mm) in a sagital view was 1.21 ± 0.31 (0.95-1.48). In all knees, the same radiological and anatomical pattern was observed, consisting of the fibers of the LMT, PFL and PML.

Conclusions. The MTPFC, formed by its three main ligaments (LMTL, PFL and PML) can be easily identified by MRI, with a constant morphological and anatomical pattern. More studies are required to evaluate whether MRI can be useful for the diagnosis and study of lesions that affect the peripheral structures of the lateral meniscus body.